diff --git a/libc/calls/_timespec_sleep.c b/libc/calls/_timespec_sleep.c
index 472241876..d660712c1 100644
--- a/libc/calls/_timespec_sleep.c
+++ b/libc/calls/_timespec_sleep.c
@@ -32,7 +32,7 @@ struct timespec _timespec_sleep(struct timespec delay) {
   if (!(rc = clock_nanosleep(CLOCK_REALTIME, 0, &delay, &remain))) {
     return (struct timespec){0};
   } else {
-    _npassert(rc == EINTR);
+    _npassert(rc == EINTR || rc == ECANCELED);
     return remain;
   }
 }
diff --git a/libc/calls/_timespec_sleep_until.c b/libc/calls/_timespec_sleep_until.c
index 088cdb6e8..f4c5adfe3 100644
--- a/libc/calls/_timespec_sleep_until.c
+++ b/libc/calls/_timespec_sleep_until.c
@@ -27,9 +27,9 @@
  *
  * @return 0 on success, or EINTR if interrupted
  */
-int _timespec_sleep_until(struct timespec abs_deadline) {
+errno_t _timespec_sleep_until(struct timespec abs_deadline) {
   int rc;
   rc = clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &abs_deadline, 0);
-  _npassert(!rc || rc == EINTR);
+  _npassert(!rc || rc == EINTR || rc == ECANCELED);
   return rc;
 }
diff --git a/libc/calls/blockcancel.internal.h b/libc/calls/blockcancel.internal.h
new file mode 100644
index 000000000..e3baf981e
--- /dev/null
+++ b/libc/calls/blockcancel.internal.h
@@ -0,0 +1,19 @@
+#ifndef COSMOPOLITAN_LIBC_CALLS_BLOCKCANCEL_H_
+#define COSMOPOLITAN_LIBC_CALLS_BLOCKCANCEL_H_
+#include "libc/thread/thread.h"
+#if !(__ASSEMBLER__ + __LINKER__ + 0)
+COSMOPOLITAN_C_START_
+
+#define BLOCK_CANCELLATIONS \
+  do {                      \
+    int _CancelState;       \
+  pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &_CancelState)
+
+#define ALLOW_CANCELLATIONS                \
+  pthread_setcancelstate(_CancelState, 0); \
+  }                                        \
+  while (0)
+
+COSMOPOLITAN_C_END_
+#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
+#endif /* COSMOPOLITAN_LIBC_CALLS_BLOCKCANCEL_H_ */
diff --git a/libc/calls/blocksigs.internal.h b/libc/calls/blocksigs.internal.h
index 1886f02c1..b4747498f 100644
--- a/libc/calls/blocksigs.internal.h
+++ b/libc/calls/blocksigs.internal.h
@@ -1,5 +1,5 @@
-#ifndef COSMOPOLITAN_LIBC_CALLS_BLOCKSIGS_INTERNAL_H_
-#define COSMOPOLITAN_LIBC_CALLS_BLOCKSIGS_INTERNAL_H_
+#ifndef COSMOPOLITAN_LIBC_CALLS_BLOCKSIGS_H_
+#define COSMOPOLITAN_LIBC_CALLS_BLOCKSIGS_H_
 #include "libc/calls/struct/sigset.h"
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 COSMOPOLITAN_C_START_
@@ -16,4 +16,4 @@ COSMOPOLITAN_C_START_
 
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
-#endif /* COSMOPOLITAN_LIBC_CALLS_BLOCKSIGS_INTERNAL_H_ */
+#endif /* COSMOPOLITAN_LIBC_CALLS_BLOCKSIGS_H_ */
diff --git a/libc/calls/fcntl.c b/libc/calls/fcntl.c
index f27beb4e9..8a5adfd89 100644
--- a/libc/calls/fcntl.c
+++ b/libc/calls/fcntl.c
@@ -112,7 +112,7 @@ int fcntl(int fd, int cmd, ...) {
       if (fd < g_fds.n && g_fds.p[fd].kind == kFdZip) {
         rc = _weaken(__zipos_fcntl)(fd, cmd, arg);
       } else if (!IsWindows()) {
-        if (cmd == F_SETLKW) {
+        if (cmd == F_SETLKW || cmd == F_OFD_SETLKW) {
           rc = sys_fcntl(fd, cmd, arg, __sys_fcntl_cp);
         } else {
           rc = sys_fcntl(fd, cmd, arg, __sys_fcntl);
diff --git a/libc/calls/openpty.c b/libc/calls/openpty.c
index 779512cf3..13bedb0dd 100644
--- a/libc/calls/openpty.c
+++ b/libc/calls/openpty.c
@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
+#include "libc/calls/blockcancel.internal.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/ioctl.h"
 #include "libc/calls/struct/metatermios.internal.h"
@@ -43,31 +44,12 @@ struct IoctlPtmGet {
   char sname[16];
 };
 
-/**
- * Opens new pseudo teletypewriter.
- *
- * @param mfd receives controlling tty rw fd on success
- * @param sfd receives subordinate tty rw fd on success
- * @param tio may be passed to tune a century of legacy behaviors
- * @param wsz may be passed to set terminal display dimensions
- * @params flags is usually O_RDWR|O_NOCTTY
- * @return 0 on success, or -1 w/ errno
- */
-int openpty(int *mfd, int *sfd, char *name, const struct termios *tio,
-            const struct winsize *wsz) {
+static int openpty_impl(int *mfd, int *sfd, char *name,
+                        const struct termios *tio,  //
+                        const struct winsize *wsz) {
   int m, s, p;
   union metatermios mt;
   struct IoctlPtmGet t;
-  if (IsWindows() || IsMetal()) {
-    return enosys();
-  }
-  if (IsAsan() && (!__asan_is_valid(mfd, sizeof(int)) ||
-                   !__asan_is_valid(sfd, sizeof(int)) ||
-                   (name && !__asan_is_valid(name, 16)) ||
-                   (tio && !__asan_is_valid(tio, sizeof(*tio))) ||
-                   (wsz && !__asan_is_valid(wsz, sizeof(*wsz))))) {
-    return efault();
-  }
   RETURN_ON_ERROR((m = posix_openpt(O_RDWR | O_NOCTTY)));
   if (!IsOpenbsd()) {
     RETURN_ON_ERROR(grantpt(m));
@@ -90,3 +72,33 @@ OnError:
   if (m != -1) sys_close(m);
   return -1;
 }
+
+/**
+ * Opens new pseudo teletypewriter.
+ *
+ * @param mfd receives controlling tty rw fd on success
+ * @param sfd receives subordinate tty rw fd on success
+ * @param tio may be passed to tune a century of legacy behaviors
+ * @param wsz may be passed to set terminal display dimensions
+ * @params flags is usually O_RDWR|O_NOCTTY
+ * @return 0 on success, or -1 w/ errno
+ */
+int openpty(int *mfd, int *sfd, char *name,  //
+            const struct termios *tio,       //
+            const struct winsize *wsz) {
+  int rc;
+  if (IsWindows() || IsMetal()) {
+    return enosys();
+  }
+  if (IsAsan() && (!__asan_is_valid(mfd, sizeof(int)) ||
+                   !__asan_is_valid(sfd, sizeof(int)) ||
+                   (name && !__asan_is_valid(name, 16)) ||
+                   (tio && !__asan_is_valid(tio, sizeof(*tio))) ||
+                   (wsz && !__asan_is_valid(wsz, sizeof(*wsz))))) {
+    return efault();
+  }
+  BLOCK_CANCELLATIONS;
+  rc = openpty(mfd, sfd, name, tio, wsz);
+  ALLOW_CANCELLATIONS;
+  return rc;
+}
diff --git a/libc/intrin/assertfail.greg.c b/libc/intrin/assertfail.greg.c
index 725842ea2..fe80c9271 100644
--- a/libc/intrin/assertfail.greg.c
+++ b/libc/intrin/assertfail.greg.c
@@ -27,6 +27,7 @@
 #include "libc/log/internal.h"
 #include "libc/runtime/runtime.h"
 #include "libc/runtime/symbols.internal.h"
+#include "libc/thread/thread.h"
 
 relegated void __assert_fail(const char *expr, const char *file, int line) {
   int me, owner;
@@ -36,6 +37,7 @@ relegated void __assert_fail(const char *expr, const char *file, int line) {
     ftrace_enabled(-1);
     owner = 0;
     me = sys_gettid();
+    pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, 0);
     kprintf("%s:%d: assert(%s) failed (tid %d)\n", file, line, expr, me);
     if (__vforked ||
         atomic_compare_exchange_strong_explicit(
diff --git a/libc/thread/pthread_cleanup_pop.c b/libc/intrin/pthread_cleanup_pop.c
similarity index 92%
rename from libc/thread/pthread_cleanup_pop.c
rename to libc/intrin/pthread_cleanup_pop.c
index f8bb41e0f..fba3b853e 100644
--- a/libc/thread/pthread_cleanup_pop.c
+++ b/libc/intrin/pthread_cleanup_pop.c
@@ -22,9 +22,11 @@
 #include "libc/thread/tls.h"
 
 void _pthread_cleanup_pop(struct _pthread_cleanup_buffer *cb, int execute) {
-  struct PosixThread *pt = (struct PosixThread *)__get_tls()->tib_pthread;
-  _unassert(cb == pt->cleanup);
-  pt->cleanup = cb->__prev;
+  struct PosixThread *pt;
+  if (__tls_enabled && (pt = (struct PosixThread *)__get_tls()->tib_pthread)) {
+    _unassert(cb == pt->cleanup);
+    pt->cleanup = cb->__prev;
+  }
   if (execute) {
     cb->__routine(cb->__arg);
   }
diff --git a/libc/thread/pthread_cleanup_push.c b/libc/intrin/pthread_cleanup_push.c
similarity index 91%
rename from libc/thread/pthread_cleanup_push.c
rename to libc/intrin/pthread_cleanup_push.c
index dd5428968..519345072 100644
--- a/libc/thread/pthread_cleanup_push.c
+++ b/libc/intrin/pthread_cleanup_push.c
@@ -18,12 +18,15 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/thread/posixthread.internal.h"
 #include "libc/thread/thread.h"
+#include "libc/thread/tls.h"
 
 void _pthread_cleanup_push(struct _pthread_cleanup_buffer *cb,
                            void (*routine)(void *), void *arg) {
-  struct PosixThread *pt = (struct PosixThread *)__get_tls()->tib_pthread;
+  struct PosixThread *pt;
   cb->__routine = routine;
   cb->__arg = arg;
-  cb->__prev = pt->cleanup;
-  pt->cleanup = cb;
+  if (__tls_enabled && (pt = (struct PosixThread *)__get_tls()->tib_pthread)) {
+    cb->__prev = pt->cleanup;
+    pt->cleanup = cb;
+  }
 }
diff --git a/libc/thread/pthread_setcancelstate.c b/libc/intrin/pthread_setcancelstate.c
similarity index 76%
rename from libc/thread/pthread_setcancelstate.c
rename to libc/intrin/pthread_setcancelstate.c
index 7889c07a2..97364ae94 100644
--- a/libc/thread/pthread_setcancelstate.c
+++ b/libc/intrin/pthread_setcancelstate.c
@@ -43,30 +43,36 @@
  * @raise EINVAL if `state` has bad value
  * @asyncsignalsafe
  */
-int pthread_setcancelstate(int state, int *oldstate) {
+errno_t pthread_setcancelstate(int state, int *oldstate) {
   struct PosixThread *pt;
-  switch (state) {
-    case PTHREAD_CANCEL_ENABLE:
-    case PTHREAD_CANCEL_DISABLE:
-    case PTHREAD_CANCEL_MASKED:
-      pt = (struct PosixThread *)__get_tls()->tib_pthread;
-      if (oldstate) {
-        if (pt->flags & PT_NOCANCEL) {
-          *oldstate = PTHREAD_CANCEL_DISABLE;
-        } else if (pt->flags & PT_MASKED) {
-          *oldstate = PTHREAD_CANCEL_MASKED;
-        } else {
-          *oldstate = PTHREAD_CANCEL_ENABLE;
+  if (__tls_enabled && (pt = (struct PosixThread *)__get_tls()->tib_pthread)) {
+    switch (state) {
+      case PTHREAD_CANCEL_ENABLE:
+      case PTHREAD_CANCEL_DISABLE:
+      case PTHREAD_CANCEL_MASKED:
+        if (oldstate) {
+          if (pt->flags & PT_NOCANCEL) {
+            *oldstate = PTHREAD_CANCEL_DISABLE;
+          } else if (pt->flags & PT_MASKED) {
+            *oldstate = PTHREAD_CANCEL_MASKED;
+          } else {
+            *oldstate = PTHREAD_CANCEL_ENABLE;
+          }
         }
-      }
-      pt->flags &= ~(PT_NOCANCEL | PT_MASKED);
-      if (state == PTHREAD_CANCEL_MASKED) {
-        pt->flags |= PT_MASKED;
-      } else if (state == PTHREAD_CANCEL_DISABLE) {
-        pt->flags |= PT_NOCANCEL;
-      }
-      return 0;
-    default:
-      return EINVAL;
+        pt->flags &= ~(PT_NOCANCEL | PT_MASKED);
+        if (state == PTHREAD_CANCEL_MASKED) {
+          pt->flags |= PT_MASKED;
+        } else if (state == PTHREAD_CANCEL_DISABLE) {
+          pt->flags |= PT_NOCANCEL;
+        }
+        return 0;
+      default:
+        return EINVAL;
+    }
+  } else {
+    if (oldstate) {
+      *oldstate = 0;
+    }
+    return 0;
   }
 }
diff --git a/libc/intrin/sys_umtx_op.S b/libc/intrin/sys_umtx_op.S
deleted file mode 100644
index 677990917..000000000
--- a/libc/intrin/sys_umtx_op.S
+++ /dev/null
@@ -1,32 +0,0 @@
-/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8     -*-│
-│vi: set et ft=asm ts=8 tw=8 fenc=utf-8                                     :vi│
-╞══════════════════════════════════════════════════════════════════════════════╡
-│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
-│                                                                              │
-│ Permission to use, copy, modify, and/or distribute this software for         │
-│ any purpose with or without fee is hereby granted, provided that the         │
-│ above copyright notice and this permission notice appear in all copies.      │
-│                                                                              │
-│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
-│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
-│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
-│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
-│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
-│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
-│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
-│ PERFORMANCE OF THIS SOFTWARE.                                                │
-╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/macros.internal.h"
-.privileged
-
-//	Calls FreeBSD's futex() API.
-//	Normalizes return value to Linux ABI -errno convention.
-sys_umtx_op:
-	mov	$0x1c6,%eax
-	mov	%rcx,%r10
-	syscall
-	jc	1f
-	ret
-1:	neg	%eax
-	ret
-	.endfn	sys_umtx_op,globl,hidden
diff --git a/libc/intrin/sys_umtx_timedwait_uint.c b/libc/intrin/sys_umtx_timedwait_uint.c
index 4b33a3422..85567eca2 100644
--- a/libc/intrin/sys_umtx_timedwait_uint.c
+++ b/libc/intrin/sys_umtx_timedwait_uint.c
@@ -20,6 +20,9 @@
 #include "libc/sysv/consts/clock.h"
 #include "libc/thread/freebsd.internal.h"
 
+int sys_umtx_timedwait_uint_cp(atomic_int *, int, int, size_t,
+                               struct _umtx_time *) asm("sys_futex_cp");
+
 int sys_umtx_timedwait_uint(atomic_int *p, int expect, bool pshare,
                             const struct timespec *abstime) {
   int op;
@@ -40,5 +43,5 @@ int sys_umtx_timedwait_uint(atomic_int *p, int expect, bool pshare,
   } else {
     op = UMTX_OP_WAIT_UINT_PRIVATE;
   }
-  return sys_umtx_op(p, op, expect, (void *)size, tm_p);
+  return sys_umtx_timedwait_uint_cp(p, op, expect, size, tm_p);
 }
diff --git a/libc/log/die.c b/libc/log/die.c
index a69acf3f1..ce371564b 100644
--- a/libc/log/die.c
+++ b/libc/log/die.c
@@ -29,6 +29,7 @@
 #include "libc/log/log.h"
 #include "libc/runtime/internal.h"
 #include "libc/runtime/runtime.h"
+#include "libc/thread/thread.h"
 
 #if SupportsMetal()
 STATIC_YOINK("_idt");
@@ -45,6 +46,7 @@ relegated wontreturn void __die(void) {
   static atomic_int once;
   owner = 0;
   me = sys_gettid();
+  pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, 0);
   if (__vforked ||
       atomic_compare_exchange_strong_explicit(
           &once, &owner, me, memory_order_relaxed, memory_order_relaxed)) {
diff --git a/libc/log/oncrash.c b/libc/log/oncrash.c
index 8a17e1435..2d4a79db3 100644
--- a/libc/log/oncrash.c
+++ b/libc/log/oncrash.c
@@ -43,6 +43,7 @@
 #include "libc/runtime/runtime.h"
 #include "libc/stdio/stdio.h"
 #include "libc/str/str.h"
+#include "libc/thread/thread.h"
 #include "libc/thread/tls.h"
 #include "third_party/libcxx/math.h"
 
@@ -307,6 +308,7 @@ relegated void __oncrash(int sig, struct siginfo *si, ucontext_t *ctx) {
   strace_enabled(-1);
   owner = 0;
   me = sys_gettid();
+  pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, 0);
   if (atomic_compare_exchange_strong_explicit(
           &once, &owner, me, memory_order_relaxed, memory_order_relaxed)) {
     if (!__vforked) {
diff --git a/libc/log/startfatal.c b/libc/log/startfatal.c
index 3fe945c48..f3334ccef 100644
--- a/libc/log/startfatal.c
+++ b/libc/log/startfatal.c
@@ -20,6 +20,7 @@
 #include "libc/intrin/safemacros.internal.h"
 #include "libc/log/internal.h"
 #include "libc/runtime/runtime.h"
+#include "libc/thread/thread.h"
 
 /**
  * Prints initial part of fatal message.
@@ -27,6 +28,7 @@
  * @note this is support code for __check_fail(), __assert_fail(), etc.
  */
 relegated void __start_fatal(const char *file, int line) {
+  pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, 0);
   __restore_tty();
   kprintf("%r%serror%s:%s:%d:%s%s: ", !__nocolor ? "\e[J\e[30;101m" : "",
           !__nocolor ? "\e[94;49m" : "", file, line,
diff --git a/libc/sock/syslog.c b/libc/sock/syslog.c
index 0308fd326..4b2f8a255 100644
--- a/libc/sock/syslog.c
+++ b/libc/sock/syslog.c
@@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/blockcancel.internal.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/dprintf.h"
 #include "libc/calls/struct/timespec.h"
@@ -124,16 +125,13 @@ void vsyslog(int priority, const char *message, va_list ap) {
   int l, l2;
   int hlen; /* If LOG_CONS is specified, use to store the point in
              * the header message after the timestamp */
-
+  BLOCK_CANCELLATIONS;
   if (log_fd < 0) __openlog();
-
   if (!(priority & LOG_FACMASK)) priority |= log_facility;
-
   /* Build the time string */
   now = Time(NULL);
   gmtime_r(&now, &tm);
   strftime(timebuf, sizeof(timebuf), "%b %e %T", &tm);
-
   pid = (log_opt & LOG_PID) ? getpid() : 0;
   /* This is a clever trick to optionally include "[<pid>]"
    * only if pid != 0. When pid==0, the while "[%.0d]" is skipped:
@@ -149,7 +147,6 @@ void vsyslog(int priority, const char *message, va_list ap) {
   l += snprintf(buf + l, sizeof(buf) - l, "%hs%s%.0d%s: ", log_ident,
                 "[" + !pid, pid, "]" + !pid);
   errno = errno_save;
-
   /* Append user message */
   l2 = vsnprintf(buf + l, sizeof(buf) - l, message, ap);
   if (l2 >= 0) {
@@ -166,37 +163,17 @@ void vsyslog(int priority, const char *message, va_list ap) {
        * - First try to send it to syslogd
        * - If fails and LOG_CONS is provided, writes to /dev/console
        */
-
-#if 0
-      if (send(log_fd, buf, l, 0) < 0 && (!is_lost_conn(errno)
-            || connect(log_fd, (void *)&log_addr, sizeof(log_addr)) < 0
-            || send(log_fd, buf, l, 0) < 0)
-          && (log_opt & LOG_CONS)) {
-        int fd = open("/dev/console", O_WRONLY|O_NOCTTY);
+      if (send(log_fd, buf, l, 0) < 0 &&
+          (!is_lost_conn(errno) ||
+           connect(log_fd, (void *)&log_addr, sizeof(log_addr)) < 0 ||
+           send(log_fd, buf, l, 0) < 0) &&
+          (log_opt & LOG_CONS)) {
+        int fd = open("/dev/console", O_WRONLY | O_NOCTTY);
         if (fd >= 0) {
-          dprintf(fd, "%.*s", l-hlen, buf+hlen);
+          dprintf(fd, "%.*s", l - hlen, buf + hlen);
           close(fd);
         }
       }
-#else
-      int rc = send(log_fd, buf, l, 0);
-      if (rc < 0) {
-        printf("ERR: send(1) failed: %s (errno=%d)\n", strerror(errno), errno);
-        if (!is_lost_conn(errno)) {
-          rc = connect(log_fd, (void *)&log_addr, sizeof(log_addr));
-          if (rc < 0) {
-            printf("ERR: connect(syslog) failed: %s (errno=%d)\n",
-                   strerror(errno), errno);
-          } else {
-            rc = send(log_fd, buf, l, 0);
-            if (rc < 0) {
-              printf("ERR: send(2) failed: %s (errno=%d)\n", strerror(errno),
-                     errno);
-            }
-          }
-        }
-      }
-#endif
     } else {
       uint16_t evtType;
       uint32_t evtID;
@@ -229,11 +206,11 @@ void vsyslog(int priority, const char *message, va_list ap) {
                    NULL /* Arguments */);
       ++log_id;
     }
-
     if (log_opt & LOG_PERROR) {
       dprintf(2, "%.*s", l - hlen, buf + hlen);
     }
   }
+  ALLOW_CANCELLATIONS;
 }
 
 /**
@@ -250,9 +227,7 @@ void vsyslog(int priority, const char *message, va_list ap) {
  */
 int setlogmask(int maskpri) {
   int ret;
-  if (log_facility == -1) {
-    __initlog();
-  }
+  if (log_facility == -1) __initlog();
   ret = log_mask;
   if (maskpri) log_mask = LOG_PRI(maskpri);
   return ret;
@@ -287,19 +262,15 @@ int setlogmask(int maskpri) {
  */
 void openlog(const char *ident, int opt, int facility) {
   size_t n;
-
-  if (log_facility == -1) {
-    __initlog();
-  }
-  if (!ident) {
-    ident = firstnonnull(program_invocation_short_name, "unknown");
-  }
+  BLOCK_CANCELLATIONS;
+  if (log_facility == -1) __initlog();
+  if (!ident) ident = firstnonnull(program_invocation_short_name, "unknown");
   tprecode8to16(log_ident, ARRAYLEN(log_ident), ident);
   log_opt = opt;
   log_facility = facility;
   log_id = 0;
-
   if ((opt & LOG_NDELAY) && log_fd < 0) __openlog();
+  ALLOW_CANCELLATIONS;
 }
 
 /**
@@ -339,13 +310,12 @@ void closelog(void) {
   if (log_facility == -1) {
     __initlog();
   }
-  if (log_fd == -1) {
-    return;
+  if (log_fd != -1) {
+    if (IsWindows()) {
+      DeregisterEventSource(log_fd);
+    } else {
+      close(log_fd);
+    }
+    log_fd = -1;
   }
-  if (IsWindows()) {
-    DeregisterEventSource(log_fd);
-  } else {
-    close(log_fd);
-  }
-  log_fd = -1;
 }
diff --git a/libc/stdio/getentropy.c b/libc/stdio/getentropy.c
index 816189b85..6e1070beb 100644
--- a/libc/stdio/getentropy.c
+++ b/libc/stdio/getentropy.c
@@ -16,13 +16,21 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/blockcancel.internal.h"
 #include "libc/stdio/rand.h"
-#include "libc/sysv/consts/grnd.h"
+#include "libc/sysv/errfuns.h"
 
 /**
  * Returns random seeding bytes, the XNU/OpenBSD way.
+ *
+ * @return 0 on success, or -1 w/ errno
+ * @raise EIO if more than 256 bytes are requested
  * @see getrandom()
  */
 int getentropy(void *buf, size_t size) {
-  return getrandom(buf, size, GRND_RANDOM);
+  if (size > 256) return eio();
+  BLOCK_CANCELLATIONS;
+  if (getrandom(buf, size, 0) != size) notpossible;
+  ALLOW_CANCELLATIONS;
+  return 0;
 }
diff --git a/libc/stdio/getrandom.c b/libc/stdio/getrandom.c
index 1acef9f25..6050cde77 100644
--- a/libc/stdio/getrandom.c
+++ b/libc/stdio/getrandom.c
@@ -41,9 +41,44 @@
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/consts/sig.h"
 #include "libc/sysv/errfuns.h"
+#include "libc/thread/thread.h"
 
 static bool have_getrandom;
 
+static ssize_t GetDevRandom(char *p, size_t n) {
+  int fd;
+  ssize_t rc;
+  fd = __sys_openat(AT_FDCWD, "/dev/urandom", O_RDONLY | O_CLOEXEC, 0);
+  if (fd == -1) return -1;
+  pthread_cleanup_push((void *)sys_close, (void *)(intptr_t)fd);
+  rc = sys_read(fd, p, n);
+  pthread_cleanup_pop(1);
+  close(fd);
+  return rc;
+}
+
+static ssize_t GetKernArnd(char *p, size_t n) {
+  size_t m, i = 0;
+  int cmd[2];
+  if (IsFreebsd()) {
+    cmd[0] = 1;  /* CTL_KERN */
+    cmd[1] = 37; /* KERN_ARND */
+  } else {
+    cmd[0] = 1;  /* CTL_KERN */
+    cmd[1] = 81; /* KERN_ARND */
+  }
+  for (;;) {
+    m = n - i;
+    if (sys_sysctl(cmd, 2, p + i, &m, 0, 0) != -1) {
+      if ((i += m) == n) {
+        return n;
+      }
+    } else {
+      return i ? i : -1;
+    }
+  }
+}
+
 /**
  * Returns cryptographic random data.
  *
@@ -76,37 +111,17 @@ static bool have_getrandom;
  * @vforksafe
  */
 ssize_t getrandom(void *p, size_t n, unsigned f) {
-  char cf;
   ssize_t rc;
-  uint64_t x;
-  int fd, cmd[2];
-  size_t i, j, m;
   const char *via;
-  sigset_t neu, old;
-  if (n > 256) n = 256;
   if ((f & ~(GRND_RANDOM | GRND_NONBLOCK))) {
     rc = einval();
     via = "n/a";
   } else if (IsWindows()) {
     via = "RtlGenRandom";
-    if (RtlGenRandom(p, n)) {
-      rc = n;
-    } else {
-      rc = __winerr();
-    }
+    rc = RtlGenRandom(p, n) ? n : __winerr();
   } else if (IsFreebsd() || IsNetbsd()) {
     via = "KERN_ARND";
-    if (IsFreebsd()) {
-      cmd[0] = 1;  /* CTL_KERN */
-      cmd[1] = 37; /* KERN_ARND */
-    } else {
-      cmd[0] = 1;  /* CTL_KERN */
-      cmd[1] = 81; /* KERN_ARND */
-    }
-    m = n;
-    if ((rc = sys_sysctl(cmd, 2, p, &m, 0, 0)) != -1) {
-      rc = m;
-    }
+    rc = GetKernArnd(p, n);
   } else if (have_getrandom) {
     via = "getrandom";
     if ((rc = sys_getrandom(p, n, f & (GRND_RANDOM | GRND_NONBLOCK))) != -1) {
@@ -114,15 +129,9 @@ ssize_t getrandom(void *p, size_t n, unsigned f) {
         rc = n;
       }
     }
-  } else if ((fd = __sys_openat(
-                  AT_FDCWD,
-                  (via = (f & GRND_RANDOM) ? "/dev/random" : "/dev/urandom"),
-                  O_RDONLY | ((f & GRND_NONBLOCK) ? O_NONBLOCK : 0), 0)) !=
-             -1) {
-    rc = sys_read(fd, p, n);
-    sys_close(fd);
   } else {
-    rc = enosys();
+    via = "/dev/urandom";
+    rc = GetDevRandom(p, n);
   }
   STRACE("getrandom(%p, %'zu, %#x) via %s → %'ld% m", p, n, f, via, rc);
   return rc;
diff --git a/libc/sysv/calls/sys_futex.s b/libc/sysv/calls/sys_futex.s
index db56b252d..0248bff55 100644
--- a/libc/sysv/calls/sys_futex.s
+++ b/libc/sysv/calls/sys_futex.s
@@ -1,2 +1,2 @@
 .include "o/libc/sysv/macros.internal.inc"
-.scall sys_futex,0x0a6053fffffff0ca,globl,hidden
+.scall sys_futex,0x0a60531c6ffff0ca,globl,hidden
diff --git a/libc/sysv/calls/sys_futex_cp.s b/libc/sysv/calls/sys_futex_cp.s
new file mode 100644
index 000000000..0538a5cfa
--- /dev/null
+++ b/libc/sysv/calls/sys_futex_cp.s
@@ -0,0 +1,2 @@
+.include "o/libc/sysv/macros.internal.inc"
+.scall sys_futex_cp,0x8a68539c6ffff8ca,globl,hidden
diff --git a/libc/sysv/consts.sh b/libc/sysv/consts.sh
index 20334d0d5..075963a2a 100755
--- a/libc/sysv/consts.sh
+++ b/libc/sysv/consts.sh
@@ -1826,7 +1826,7 @@ syscon	nr	__NR_kill				0x003e			0x2000025		0x0025			0x007a			0x025			0xfff
 syscon	nr	__NR_killpg				0xfff			0xfff			0x0092			0xfff			0xfff			0xfff
 syscon	nr	__NR_clone				0x0038			0xfff			0xfff			0xfff			0x11f			0xfff
 syscon	nr	__NR_tkill				0x00c8			0xfff			0xfff			0xfff			0xfff			0xfff
-syscon	nr	__NR_futex				0x00ca			0xfff			0xfff			0x0053			0xfff			0xfff
+syscon	nr	__NR_futex				0x00ca			0xfff			0x1c6			0x0053			0x0a6			0xfff
 syscon	nr	__NR_set_robust_list			0x0111			0xfff			0xfff			0xfff			0x0a7			0xfff
 syscon	nr	__NR_get_robust_list			0x0112			0xfff			0xfff			0xfff			0x0a8			0xfff
 syscon	nr	__NR_uname				0x003f			0xfff			0x00a4			0xfff			0xfff			0xfff
diff --git a/libc/sysv/consts/__NR_futex.s b/libc/sysv/consts/__NR_futex.s
index a7bd77d79..61c7a2ff5 100644
--- a/libc/sysv/consts/__NR_futex.s
+++ b/libc/sysv/consts/__NR_futex.s
@@ -1,2 +1,2 @@
 .include "o/libc/sysv/consts/syscon.internal.inc"
-.syscon nr,__NR_futex,0x00ca,0xfff,0xfff,0x0053,0xfff,0xfff
+.syscon nr,__NR_futex,0x00ca,0xfff,0x1c6,0x0053,0x0a6,0xfff
diff --git a/libc/sysv/syscalls.sh b/libc/sysv/syscalls.sh
index 8cab83c6a..2d338097b 100755
--- a/libc/sysv/syscalls.sh
+++ b/libc/sysv/syscalls.sh
@@ -51,7 +51,7 @@ scall	__sys_munmap		0x049049049204900b	globl hidden
 scall	sys_sigaction		0x15402e1a0202e00d	globl hidden # rt_sigaction on Lunix; __sigaction_sigtramp() on NetBSD
 scall	__sys_sigprocmask	0x125030154214900e	globl hidden # a.k.a. rt_sigprocmask, openbsd:byvalue, a.k.a. pthread_sigmask
 scall	sys_ioctl		0x0360360362036010	globl hidden
-scall	sys_ioctl_cp		0x8368368362836810	globl hidden
+scall	sys_ioctl_cp		0x8368368362836810	globl hidden # intended for TCSBRK
 scall	sys_pread		0x8ad8ad9db2899811	globl hidden # a.k.a. pread64; netbsd+openbsd:pad
 scall	sys_pwrite		0x8ae8ae9dc289a812	globl hidden # a.k.a. pwrite64; netbsd+openbsd:pad
 scall	sys_readv		0x8788788782878813	globl hidden
@@ -101,7 +101,8 @@ scall	sys_kill		0x02507a025202503e	globl hidden # kill(pid, sig, 1) b/c xnu
 scall	sys_killpg		0x092fff092fffffff	globl hidden
 scall	sys_clone		0x11fffffffffff038	globl hidden
 scall	sys_tkill		0x13e0771b121480c8	globl hidden # thr_kill() on freebsd; _lwp_kill() on netbsd; thrkill() on openbsd where arg3 should be 0; __pthread_kill() on XNU
-scall	sys_futex		0x0a6053fffffff0ca	globl hidden # raises SIGSYS on NetBSD
+scall	sys_futex		0x0a60531c6ffff0ca	globl hidden # raises SIGSYS on NetBSD; _umtx_op() on FreeBSD
+scall	sys_futex_cp		0x8a68539c6ffff8ca	globl hidden # intended for futex wait ops
 scall	sys_set_robust_list	0x0a7ffffffffff111	globl # no wrapper
 scall	sys_get_robust_list	0x0a8ffffffffff112	globl # no wrapper
 scall	sys_uname		0x0a4fff0a4ffff03f	globl hidden
@@ -114,7 +115,7 @@ scall	sys_msgsnd		0x8e28e28e22904845	globl # no wrapper; won't polyfill for wind
 scall	sys_msgrcv		0x8e38e38e32905846	globl # no wrapper; won't polyfill for windows
 scall	sys_msgctl		0x1bc1291ff2102047	globl # no wrapper; won't polyfill for windows
 scall	__sys_fcntl		0x05c05c05c205c048	globl hidden
-scall	__sys_fcntl_cp		0x85c85c85c285c848	globl hidden
+scall	__sys_fcntl_cp		0x85c85c85c285c848	globl hidden # intended for F_SETLKW and F_OFD_SETLKW
 scall	sys_flock		0x8838838832883849	globl hidden
 scall	sys_fsync		0x85f85f85f285f84a	globl hidden
 scall	sys_fdatasync		0x8f185fa2628bb84b	globl hidden # fsync() on openbsd
diff --git a/libc/testlib/testrunner.c b/libc/testlib/testrunner.c
index 8e3f44166..92aa966b3 100644
--- a/libc/testlib/testrunner.c
+++ b/libc/testlib/testrunner.c
@@ -225,6 +225,7 @@ void testlib_runtestcases(testfn_t *start, testfn_t *end, testfn_t warmup) {
     if (!IsWindows()) sys_getpid();
     if (warmup) warmup();
     testlib_clearxmmregisters();
+    STRACE("running test %t", fn);
     (*fn)();
     if (!IsWindows()) sys_getpid();
     if (_weaken(TearDown)) _weaken(TearDown)();
diff --git a/libc/thread/freebsd.internal.h b/libc/thread/freebsd.internal.h
index 5134a108d..d6473c231 100644
--- a/libc/thread/freebsd.internal.h
+++ b/libc/thread/freebsd.internal.h
@@ -48,7 +48,6 @@ struct _umtx_time {
   uint32_t _clockid;
 };
 
-int sys_umtx_op(void *, int, unsigned long, void *, void *);
 int sys_umtx_timedwait_uint(_Atomic(int) *, int, bool, const struct timespec *);
 
 COSMOPOLITAN_C_END_
diff --git a/libc/thread/posixthread.internal.h b/libc/thread/posixthread.internal.h
index b63df05af..e09f50a28 100644
--- a/libc/thread/posixthread.internal.h
+++ b/libc/thread/posixthread.internal.h
@@ -15,8 +15,8 @@
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 COSMOPOLITAN_C_START_
 
-// LEGAL TRANSITIONS             ┌──> TERMINATED
-// pthread_create ─┬─> JOINABLE ─┴┬─> DETACHED ──> ZOMBIE
+// LEGAL TRANSITIONS             ┌──> TERMINATED ─┐
+// pthread_create ─┬─> JOINABLE ─┴┬─> DETACHED ───┴─> ZOMBIE
 //                 └──────────────┘
 enum PosixThreadStatus {
 
@@ -47,6 +47,8 @@ enum PosixThreadStatus {
   //
   // - kPosixThreadTerminated -> _pthread_free() will happen when
   //   pthread_join() is called by the user.
+  // - kPosixThreadTerminated -> kPosixThreadZombie will happen when
+  //   pthread_detach() is called by the user.
   kPosixThreadTerminated,
 
   // this is a detached thread that terminated.
@@ -83,10 +85,10 @@ extern _Atomic(pthread_key_dtor) _pthread_key_dtor[PTHREAD_KEYS_MAX] hidden;
 int _pthread_atfork(atfork_f, atfork_f, atfork_f) hidden;
 int _pthread_reschedule(struct PosixThread *) hidden;
 int _pthread_setschedparam_freebsd(int, int, const struct sched_param *) hidden;
+int _pthread_wait(struct PosixThread *) hidden;
 void _pthread_free(struct PosixThread *) hidden;
 void _pthread_cleanup(struct PosixThread *) hidden;
 void _pthread_ungarbage(void) hidden;
-void _pthread_wait(struct PosixThread *) hidden;
 void _pthread_zombies_add(struct PosixThread *) hidden;
 void _pthread_zombies_purge(void) hidden;
 void _pthread_zombies_decimate(void) hidden;
diff --git a/libc/thread/pthread_atfork.c b/libc/thread/pthread_atfork.c
index 2b3a69324..a19b86e05 100644
--- a/libc/thread/pthread_atfork.c
+++ b/libc/thread/pthread_atfork.c
@@ -65,8 +65,11 @@ void _pthread_onfork_parent(void) {
 }
 
 void _pthread_onfork_child(void) {
+  pthread_mutexattr_t attr;
   extern pthread_mutex_t __mmi_lock_obj;
-  bzero(&__mmi_lock_obj, sizeof(__mmi_lock_obj));
+  pthread_mutexattr_init(&attr);
+  pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
+  pthread_mutex_init(&__mmi_lock_obj, &attr);
   __kmalloc_unlock();
   _pthread_onfork(2);
 }
diff --git a/libc/thread/pthread_attr_destroy.c b/libc/thread/pthread_attr_destroy.c
index 299e737a1..9145233c5 100644
--- a/libc/thread/pthread_attr_destroy.c
+++ b/libc/thread/pthread_attr_destroy.c
@@ -21,8 +21,10 @@
 
 /**
  * Destroys pthread attributes.
+ *
+ * @return 0 on success, or errno on error
  */
-int pthread_attr_destroy(pthread_attr_t *attr) {
+errno_t pthread_attr_destroy(pthread_attr_t *attr) {
   memset(attr, -1, sizeof(*attr));
   return 0;
 }
diff --git a/libc/thread/pthread_attr_getdetachstate.c b/libc/thread/pthread_attr_getdetachstate.c
index 2ae2d1c0d..baf6ff126 100644
--- a/libc/thread/pthread_attr_getdetachstate.c
+++ b/libc/thread/pthread_attr_getdetachstate.c
@@ -26,7 +26,8 @@
  *     - `PTHREAD_CREATE_DETACHED`
  * @return 0 on success, or error on failure
  */
-int pthread_attr_getdetachstate(const pthread_attr_t *attr, int *detachstate) {
+errno_t pthread_attr_getdetachstate(const pthread_attr_t *attr,
+                                    int *detachstate) {
   *detachstate = attr->__detachstate;
   return 0;
 }
diff --git a/libc/thread/pthread_attr_getinheritsched.c b/libc/thread/pthread_attr_getinheritsched.c
index 97e757961..097c80825 100644
--- a/libc/thread/pthread_attr_getinheritsched.c
+++ b/libc/thread/pthread_attr_getinheritsched.c
@@ -21,8 +21,8 @@
 /**
  * Returns thread inherit schedule attribute.
  */
-int pthread_attr_getinheritsched(const pthread_attr_t *attr,
-                                 int *inheritsched) {
+errno_t pthread_attr_getinheritsched(const pthread_attr_t *attr,
+                                     int *inheritsched) {
   *inheritsched = attr->__inheritsched;
   return 0;
 }
diff --git a/libc/thread/pthread_attr_getschedparam.c b/libc/thread/pthread_attr_getschedparam.c
index 694e9629b..3f53b0c97 100644
--- a/libc/thread/pthread_attr_getschedparam.c
+++ b/libc/thread/pthread_attr_getschedparam.c
@@ -21,8 +21,8 @@
 /**
  * Gets thread scheduler parameter attribute.
  */
-int pthread_attr_getschedparam(const pthread_attr_t *attr,
-                               struct sched_param *param) {
+errno_t pthread_attr_getschedparam(const pthread_attr_t *attr,
+                                   struct sched_param *param) {
   *param = (struct sched_param){attr->__schedparam};
   return 0;
 }
diff --git a/libc/thread/pthread_attr_getschedpolicy.c b/libc/thread/pthread_attr_getschedpolicy.c
index b07164899..791ad4b90 100644
--- a/libc/thread/pthread_attr_getschedpolicy.c
+++ b/libc/thread/pthread_attr_getschedpolicy.c
@@ -21,7 +21,7 @@
 /**
  * Gets thread scheduler policy attribute
  */
-int pthread_attr_getschedpolicy(const pthread_attr_t *attr, int *policy) {
+errno_t pthread_attr_getschedpolicy(const pthread_attr_t *attr, int *policy) {
   *policy = attr->__schedpolicy;
   return 0;
 }
diff --git a/libc/thread/pthread_attr_getscope.c b/libc/thread/pthread_attr_getscope.c
index 2556481fe..e3fd27cd6 100644
--- a/libc/thread/pthread_attr_getscope.c
+++ b/libc/thread/pthread_attr_getscope.c
@@ -23,7 +23,8 @@
  *
  * @return 0 on success, or errno on error
  */
-int pthread_attr_getscope(const pthread_attr_t *attr, int *contentionscope) {
+errno_t pthread_attr_getscope(const pthread_attr_t *attr,
+                              int *contentionscope) {
   *contentionscope = attr->__contentionscope;
   return 0;
 }
diff --git a/libc/thread/pthread_attr_setdetachstate.c b/libc/thread/pthread_attr_setdetachstate.c
index 55d9edf26..f6d807eb8 100644
--- a/libc/thread/pthread_attr_setdetachstate.c
+++ b/libc/thread/pthread_attr_setdetachstate.c
@@ -34,7 +34,7 @@
  * @return 0 on success, or error on failure
  * @raises EINVAL if `detachstate` is invalid
  */
-int pthread_attr_setdetachstate(pthread_attr_t *attr, int detachstate) {
+errno_t pthread_attr_setdetachstate(pthread_attr_t *attr, int detachstate) {
   switch (detachstate) {
     case PTHREAD_CREATE_JOINABLE:
     case PTHREAD_CREATE_DETACHED:
diff --git a/libc/thread/pthread_attr_setschedparam.c b/libc/thread/pthread_attr_setschedparam.c
index 0c09a6a26..f0871c481 100644
--- a/libc/thread/pthread_attr_setschedparam.c
+++ b/libc/thread/pthread_attr_setschedparam.c
@@ -40,8 +40,8 @@
  * @see sched_get_priority_max()
  * @see sched_setparam()
  */
-int pthread_attr_setschedparam(pthread_attr_t *attr,
-                               const struct sched_param *param) {
+errno_t pthread_attr_setschedparam(pthread_attr_t *attr,
+                                   const struct sched_param *param) {
   if (!param) return EINVAL;
   attr->__schedparam = param->sched_priority;
   return 0;
diff --git a/libc/thread/pthread_attr_setschedpolicy.c b/libc/thread/pthread_attr_setschedpolicy.c
index 294573173..d839741de 100644
--- a/libc/thread/pthread_attr_setschedpolicy.c
+++ b/libc/thread/pthread_attr_setschedpolicy.c
@@ -41,7 +41,7 @@
  *       supported (Linux), otherwise it's treated as `SCHED_OTHER`
  * @see sched_setscheduler()
  */
-int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy) {
+errno_t pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy) {
   attr->__schedpolicy = policy;
   return 0;
 }
diff --git a/libc/thread/pthread_attr_setscope.c b/libc/thread/pthread_attr_setscope.c
index 648198523..9f8d4b307 100644
--- a/libc/thread/pthread_attr_setscope.c
+++ b/libc/thread/pthread_attr_setscope.c
@@ -30,7 +30,7 @@
  * @raise ENOTSUP if `contentionscope` isn't supported on host OS
  * @raise EINVAL if `contentionscope` was invalid
  */
-int pthread_attr_setscope(pthread_attr_t *attr, int contentionscope) {
+errno_t pthread_attr_setscope(pthread_attr_t *attr, int contentionscope) {
   switch (contentionscope) {
     case PTHREAD_SCOPE_SYSTEM:
       attr->__contentionscope = contentionscope;
diff --git a/libc/thread/pthread_barrier_destroy.c b/libc/thread/pthread_barrier_destroy.c
index c249bbe60..400a21198 100644
--- a/libc/thread/pthread_barrier_destroy.c
+++ b/libc/thread/pthread_barrier_destroy.c
@@ -26,7 +26,7 @@
  * @return 0 on success, or error on failure
  * @raise EINVAL if threads are still inside the barrier
  */
-int pthread_barrier_destroy(pthread_barrier_t *barrier) {
+errno_t pthread_barrier_destroy(pthread_barrier_t *barrier) {
   if (barrier->_nsync) {
     nsync_counter_free(barrier->_nsync);
     barrier->_nsync = 0;
diff --git a/libc/thread/pthread_barrier_init.c b/libc/thread/pthread_barrier_init.c
index b83a35230..041cf0023 100644
--- a/libc/thread/pthread_barrier_init.c
+++ b/libc/thread/pthread_barrier_init.c
@@ -30,8 +30,9 @@
  * @raise EINVAL if `count` isn't greater than zero
  * @raise ENOMEM if insufficient memory exists
  */
-int pthread_barrier_init(pthread_barrier_t *barrier,
-                         const pthread_barrierattr_t *attr, unsigned count) {
+errno_t pthread_barrier_init(pthread_barrier_t *barrier,
+                             const pthread_barrierattr_t *attr,
+                             unsigned count) {
   nsync_counter c;
   if (!count) return EINVAL;
   if (!(c = nsync_counter_new(count))) return ENOMEM;
diff --git a/libc/thread/pthread_barrierattr_destroy.c b/libc/thread/pthread_barrierattr_destroy.c
index 3777f2b3f..6d288c8a6 100644
--- a/libc/thread/pthread_barrierattr_destroy.c
+++ b/libc/thread/pthread_barrierattr_destroy.c
@@ -16,15 +16,15 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/thread/thread.h"
 #include "libc/str/str.h"
+#include "libc/thread/thread.h"
 
 /**
  * Destroys barrier attributes.
  *
  * @return 0 on success, or error on failure
  */
-int pthread_barrierattr_destroy(pthread_barrierattr_t *attr) {
+errno_t pthread_barrierattr_destroy(pthread_barrierattr_t *attr) {
   memset(attr, -1, sizeof(*attr));
   return 0;
 }
diff --git a/libc/thread/pthread_barrierattr_getpshared.c b/libc/thread/pthread_barrierattr_getpshared.c
index bd2c547b0..2fcb380f9 100644
--- a/libc/thread/pthread_barrierattr_getpshared.c
+++ b/libc/thread/pthread_barrierattr_getpshared.c
@@ -26,8 +26,8 @@
  *     - `PTHREAD_PROCESS_SHARED` (unsupported)
  * @return 0 on success, or error on failure
  */
-int pthread_barrierattr_getpshared(const pthread_barrierattr_t *attr,
-                                   int *pshared) {
+errno_t pthread_barrierattr_getpshared(const pthread_barrierattr_t *attr,
+                                       int *pshared) {
   *pshared = *attr;
   return 0;
 }
diff --git a/libc/thread/pthread_barrierattr_init.c b/libc/thread/pthread_barrierattr_init.c
index b009911e2..142a906a6 100644
--- a/libc/thread/pthread_barrierattr_init.c
+++ b/libc/thread/pthread_barrierattr_init.c
@@ -23,7 +23,7 @@
  *
  * @return 0 on success, or error on failure
  */
-int pthread_barrierattr_init(pthread_barrierattr_t *attr) {
+errno_t pthread_barrierattr_init(pthread_barrierattr_t *attr) {
   *attr = 0;
   return 0;
 }
diff --git a/libc/thread/pthread_barrierattr_setpshared.c b/libc/thread/pthread_barrierattr_setpshared.c
index 4ae2adbb6..594c69ac3 100644
--- a/libc/thread/pthread_barrierattr_setpshared.c
+++ b/libc/thread/pthread_barrierattr_setpshared.c
@@ -28,7 +28,8 @@
  * @return 0 on success, or error on failure
  * @raises EINVAL if `pshared` is invalid
  */
-int pthread_barrierattr_setpshared(pthread_barrierattr_t *attr, int pshared) {
+errno_t pthread_barrierattr_setpshared(pthread_barrierattr_t *attr,
+                                       int pshared) {
   switch (pshared) {
     case PTHREAD_PROCESS_PRIVATE:
       *attr = pshared;
diff --git a/libc/thread/pthread_cancel.c b/libc/thread/pthread_cancel.c
index 79371dd93..4bd51ff2a 100644
--- a/libc/thread/pthread_cancel.c
+++ b/libc/thread/pthread_cancel.c
@@ -24,6 +24,7 @@
 #include "libc/calls/ucontext.h"
 #include "libc/errno.h"
 #include "libc/intrin/atomic.h"
+#include "libc/intrin/kprintf.h"
 #include "libc/runtime/runtime.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/sa.h"
@@ -85,12 +86,12 @@ static void ListenForSigCancel(void) {
  * `writev`, `pwrite`, `pwritev`, `accept`, `connect`, `recvmsg`,
  * `sendmsg`, `recv`, `send`, `tcdrain`, `clock_nanosleep`, `fsync`,
  * `fdatasync`, `fcntl(F_SETLKW)`, `epoll`, `sigsuspend`, `msync`,
- * `wait4`, `getrandom`, `pthread_cond_timedwait` are most cancellation
- * points, plus many userspace libraries that call the above functions,
- * unless they're using pthread_setcancelstate() to temporarily disable
- * the cancellation mechanism. Some userspace functions, e.g. system()
- * and popen() will eagerly call pthread_testcancel_np() to help avoid
- * the potential for resource leaks later on.
+ * `wait4`, `getrandom`, `pthread_cond_timedwait`, and `sem_timedwait`
+ * are most cancellation points, plus many userspace libraries that call
+ * the above functions, unless they're using pthread_setcancelstate() to
+ * temporarily disable the cancellation mechanism. Some userspace
+ * functions, e.g. system() will eagerly call pthread_testcancel_np() to
+ * help avoid the potential for resource leaks later on.
  *
  * It's possible to put a thread in asynchronous cancellation mode using
  * pthread_setcanceltype(), thus allowing a cancellation to occur at any
@@ -110,7 +111,7 @@ static void ListenForSigCancel(void) {
  * @return 0 on success, or errno on error
  * @raise ESRCH if thread isn't alive
  */
-int pthread_cancel(pthread_t thread) {
+errno_t pthread_cancel(pthread_t thread) {
   int e, rc, tid;
   static bool once;
   struct PosixThread *pt;
@@ -124,9 +125,9 @@ int pthread_cancel(pthread_t thread) {
     default:
       break;
   }
-  atomic_store_explicit(&pt->cancelled, 1, memory_order_release);
+  atomic_exchange_explicit(&pt->cancelled, 1, memory_order_release);
   if (thread == __get_tls()->tib_pthread) {
-    if (!(pt->flags & PT_NOCANCEL) && (pt->flags & PT_ASYNC)) {
+    if (!(pt->flags & (PT_NOCANCEL | PT_MASKED)) && (pt->flags & PT_ASYNC)) {
       pthread_exit(PTHREAD_CANCELED);
     }
     return 0;
@@ -183,7 +184,7 @@ void pthread_testcancel(void) {
  * @return 0 if not cancelled or cancellation is blocked or `ECANCELED`
  *     in masked mode when the calling thread has been cancelled
  */
-int pthread_testcancel_np(void) {
+errno_t pthread_testcancel_np(void) {
   int rc;
   struct PosixThread *pt;
   if (!__tls_enabled) return 0;
diff --git a/libc/thread/pthread_cond_destroy.c b/libc/thread/pthread_cond_destroy.c
index 579b2399a..99b3bb81b 100644
--- a/libc/thread/pthread_cond_destroy.c
+++ b/libc/thread/pthread_cond_destroy.c
@@ -25,7 +25,7 @@
  * @return 0 on success, or error number on failure
  * @raise EINVAL if threads are still waiting on condition
  */
-int pthread_cond_destroy(pthread_cond_t *cond) {
+errno_t pthread_cond_destroy(pthread_cond_t *cond) {
   memset(cond, -1, sizeof(*cond));
   return 0;
 }
diff --git a/libc/thread/pthread_cond_init.c b/libc/thread/pthread_cond_init.c
index aa5e8e8b7..5619a7999 100644
--- a/libc/thread/pthread_cond_init.c
+++ b/libc/thread/pthread_cond_init.c
@@ -24,7 +24,8 @@
  * @param attr may be null
  * @return 0 on success, or error number on failure
  */
-int pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr) {
+errno_t pthread_cond_init(pthread_cond_t *cond,
+                          const pthread_condattr_t *attr) {
   *cond = (pthread_cond_t){0};
   return 0;
 }
diff --git a/libc/thread/pthread_cond_timedwait.c b/libc/thread/pthread_cond_timedwait.c
index 03de7b369..b213c040f 100644
--- a/libc/thread/pthread_cond_timedwait.c
+++ b/libc/thread/pthread_cond_timedwait.c
@@ -41,8 +41,9 @@
  * @raise EPERM if `mutex` is `PTHREAD_MUTEX_ERRORCHECK` and the lock
  *     isn't owned by the current thread
  * @raise EINVAL if `0 ≤ abstime->tv_nsec < 1000000000` wasn't the case
- * @see pthread_cond_broadcast
- * @see pthread_cond_signal
+ * @raise ECANCELED if calling thread was cancelled in masked mode
+ * @see pthread_cond_broadcast()
+ * @see pthread_cond_signal()
  * @cancellationpoint
  */
 errno_t pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
diff --git a/libc/thread/pthread_cond_wait.c b/libc/thread/pthread_cond_wait.c
index 6606f7787..b7a120fd1 100644
--- a/libc/thread/pthread_cond_wait.c
+++ b/libc/thread/pthread_cond_wait.c
@@ -31,6 +31,7 @@
  *
  * @param mutex needs to be held by thread when calling this function
  * @return 0 on success, or errno on error
+ * @raise ECANCELED if calling thread was cancelled in masked mode
  * @raise EPERM if `mutex` is `PTHREAD_MUTEX_ERRORCHECK` and the lock
  *     isn't owned by the current thread
  * @see pthread_cond_timedwait
diff --git a/libc/thread/pthread_condattr_destroy.c b/libc/thread/pthread_condattr_destroy.c
index abf437dd5..a1376ad0f 100644
--- a/libc/thread/pthread_condattr_destroy.c
+++ b/libc/thread/pthread_condattr_destroy.c
@@ -16,15 +16,15 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/thread/thread.h"
 #include "libc/str/str.h"
+#include "libc/thread/thread.h"
 
 /**
  * Destroys condition attributes.
  *
  * @return 0 on success, or error on failure
  */
-int pthread_condattr_destroy(pthread_condattr_t *attr) {
+errno_t pthread_condattr_destroy(pthread_condattr_t *attr) {
   memset(attr, -1, sizeof(*attr));
   return 0;
 }
diff --git a/libc/thread/pthread_condattr_getpshared.c b/libc/thread/pthread_condattr_getpshared.c
index dab698903..f9791291d 100644
--- a/libc/thread/pthread_condattr_getpshared.c
+++ b/libc/thread/pthread_condattr_getpshared.c
@@ -26,7 +26,8 @@
  *     - `PTHREAD_PROCESS_SHARED`
  * @return 0 on success, or error on failure
  */
-int pthread_condattr_getpshared(const pthread_condattr_t *attr, int *pshared) {
+errno_t pthread_condattr_getpshared(const pthread_condattr_t *attr,
+                                    int *pshared) {
   *pshared = *attr;
   return 0;
 }
diff --git a/libc/thread/pthread_condattr_init.c b/libc/thread/pthread_condattr_init.c
index 7e61998fd..ad617215c 100644
--- a/libc/thread/pthread_condattr_init.c
+++ b/libc/thread/pthread_condattr_init.c
@@ -23,7 +23,7 @@
  *
  * @return 0 on success, or error on failure
  */
-int pthread_condattr_init(pthread_condattr_t *attr) {
+errno_t pthread_condattr_init(pthread_condattr_t *attr) {
   *attr = 0;
   return 0;
 }
diff --git a/libc/thread/pthread_condattr_setpshared.c b/libc/thread/pthread_condattr_setpshared.c
index ccd7ae242..e6c261c2c 100644
--- a/libc/thread/pthread_condattr_setpshared.c
+++ b/libc/thread/pthread_condattr_setpshared.c
@@ -28,7 +28,7 @@
  * @return 0 on success, or error on failure
  * @raises EINVAL if `pshared` is invalid
  */
-int pthread_condattr_setpshared(pthread_condattr_t *attr, int pshared) {
+errno_t pthread_condattr_setpshared(pthread_condattr_t *attr, int pshared) {
   switch (pshared) {
     case PTHREAD_PROCESS_PRIVATE:
       *attr = pshared;
diff --git a/libc/thread/pthread_create.c b/libc/thread/pthread_create.c
index af8396466..339d32cb6 100644
--- a/libc/thread/pthread_create.c
+++ b/libc/thread/pthread_create.c
@@ -59,8 +59,8 @@ STATIC_YOINK("_pthread_atfork");
 #define MAP_ANON_OPENBSD  0x1000
 #define MAP_STACK_OPENBSD 0x4000
 
-void _pthread_wait(struct PosixThread *pt) {
-  _wait0(&pt->tib->tib_tid);
+errno_t _pthread_wait(struct PosixThread *pt) {
+  return _wait0(&pt->tib->tib_tid);
 }
 
 void _pthread_free(struct PosixThread *pt) {
diff --git a/libc/thread/pthread_detach.c b/libc/thread/pthread_detach.c
index fdf06dd62..24493ddf5 100644
--- a/libc/thread/pthread_detach.c
+++ b/libc/thread/pthread_detach.c
@@ -32,36 +32,29 @@
  * @returnserrno
  * @threadsafe
  */
-int pthread_detach(pthread_t thread) {
+errno_t pthread_detach(pthread_t thread) {
   struct PosixThread *pt;
-  enum PosixThreadStatus status;
-  if (!(pt = (struct PosixThread *)thread)) {
-    return EINVAL;
-  }
+  enum PosixThreadStatus status, transition;
+  if (!(pt = (struct PosixThread *)thread)) return EINVAL;
   for (;;) {
     status = atomic_load_explicit(&pt->status, memory_order_acquire);
     if (status == kPosixThreadDetached || status == kPosixThreadZombie) {
       // these two states indicate the thread was already detached, in
       // which case it's already listed under _pthread_zombies.
       return EINVAL;
-    } else if (status == kPosixThreadTerminated) {
-      // thread was joinable and finished running. since pthread_join
-      // won't be called, it's safe to free the thread resources now.
-      // POSIX says this could be reported as ESRCH but then our test
-      // code would be less elegant in order for it to avoid flaking.
-      _pthread_wait(pt);
-      _pthread_free(pt);
-      break;
     } else if (status == kPosixThreadJoinable) {
-      if (atomic_compare_exchange_weak_explicit(
-              &pt->status, &status, kPosixThreadDetached, memory_order_release,
-              memory_order_relaxed)) {
-        _pthread_zombies_add(pt);
-        break;
-      }
+      transition = kPosixThreadDetached;
+    } else if (status == kPosixThreadTerminated) {
+      transition = kPosixThreadZombie;
     } else {
       notpossible;
     }
+    if (atomic_compare_exchange_weak_explicit(&pt->status, &status, transition,
+                                              memory_order_release,
+                                              memory_order_relaxed)) {
+      _pthread_zombies_add(pt);
+      break;
+    }
   }
   return 0;
 }
diff --git a/libc/thread/pthread_getattr_np.c b/libc/thread/pthread_getattr_np.c
index 49e730696..d9742c985 100644
--- a/libc/thread/pthread_getattr_np.c
+++ b/libc/thread/pthread_getattr_np.c
@@ -47,7 +47,7 @@
  * @return 0 on success, or errno on error
  * @raise ENOMEM is listed as a possible result by LSB 5.0
  */
-int pthread_getattr_np(pthread_t thread, pthread_attr_t *attr) {
+errno_t pthread_getattr_np(pthread_t thread, pthread_attr_t *attr) {
   struct PosixThread *pt = (struct PosixThread *)thread;
   memcpy(attr, &pt->attr, sizeof(pt->attr));
   switch (atomic_load_explicit(&pt->status, memory_order_relaxed)) {
diff --git a/libc/thread/pthread_getname_np.c b/libc/thread/pthread_getname_np.c
index eeb81688a..02eeb89f7 100644
--- a/libc/thread/pthread_getname_np.c
+++ b/libc/thread/pthread_getname_np.c
@@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/blockcancel.internal.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/dce.h"
@@ -28,23 +29,7 @@
 #include "libc/sysv/consts/pr.h"
 #include "libc/thread/posixthread.internal.h"
 
-/**
- * Gets name of thread registered with system, e.g.
- *
- *     char name[64];
- *     pthread_getname_np(thread, name, sizeof(name));
- *
- * If the thread doesn't have a name, then empty string is returned.
- * This implementation guarantees `buf` is always modified, even on
- * error, and will always be nul-terminated. If `size` is 0 then this
- * function returns 0. Your `buf` is also chomped to remove newlines.
- *
- * @return 0 on success, or errno on error
- * @raise ERANGE if `size` wasn't large enough, in which case your
- *     result will still be returned truncated if possible
- * @raise ENOSYS on MacOS, Windows, FreeBSD, and OpenBSD
- */
-errno_t pthread_getname_np(pthread_t thread, char *name, size_t size) {
+static errno_t pthread_getname_impl(pthread_t thread, char *name, size_t size) {
   int fd, rc, tid, len, e = errno;
 
   if (!size) return 0;
@@ -113,3 +98,27 @@ errno_t pthread_getname_np(pthread_t thread, char *name, size_t size) {
     return ENOSYS;
   }
 }
+
+/**
+ * Gets name of thread registered with system, e.g.
+ *
+ *     char name[64];
+ *     pthread_getname_np(thread, name, sizeof(name));
+ *
+ * If the thread doesn't have a name, then empty string is returned.
+ * This implementation guarantees `buf` is always modified, even on
+ * error, and will always be nul-terminated. If `size` is 0 then this
+ * function returns 0. Your `buf` is also chomped to remove newlines.
+ *
+ * @return 0 on success, or errno on error
+ * @raise ERANGE if `size` wasn't large enough, in which case your
+ *     result will still be returned truncated if possible
+ * @raise ENOSYS on MacOS, Windows, FreeBSD, and OpenBSD
+ */
+errno_t pthread_getname_np(pthread_t thread, char *name, size_t size) {
+  errno_t rc;
+  BLOCK_CANCELLATIONS;
+  rc = pthread_getname_impl(thread, name, size);
+  ALLOW_CANCELLATIONS;
+  return rc;
+}
diff --git a/libc/thread/pthread_getschedparam.c b/libc/thread/pthread_getschedparam.c
index bd3093aa1..91ead4efc 100644
--- a/libc/thread/pthread_getschedparam.c
+++ b/libc/thread/pthread_getschedparam.c
@@ -22,8 +22,8 @@
 /**
  * Gets most recently set scheduling of thread.
  */
-int pthread_getschedparam(pthread_t thread, int *policy,
-                          struct sched_param *param) {
+errno_t pthread_getschedparam(pthread_t thread, int *policy,
+                              struct sched_param *param) {
   struct PosixThread *pt = (struct PosixThread *)thread;
   *policy = pt->attr.__schedpolicy;
   *param = (struct sched_param){pt->attr.__schedparam};
diff --git a/libc/thread/pthread_join.c b/libc/thread/pthread_join.c
index 082854970..6477f6a9c 100644
--- a/libc/thread/pthread_join.c
+++ b/libc/thread/pthread_join.c
@@ -27,14 +27,16 @@
  * @param value_ptr if non-null will receive pthread_exit() argument
  *     if the thread called pthread_exit(), or `PTHREAD_CANCELED` if
  *     pthread_cancel() destroyed the thread instead
- * @return 0 on success, or errno with error
+ * @return 0 on success, or errno on error
+ * @raise ECANCELED if calling thread was cancelled in masked mode
  * @raise EDEADLK if `thread` is the current thread
  * @raise EINVAL if `thread` is detached
  * @cancellationpoint
  * @returnserrno
  * @threadsafe
  */
-int pthread_join(pthread_t thread, void **value_ptr) {
+errno_t pthread_join(pthread_t thread, void **value_ptr) {
+  errno_t rc;
   struct PosixThread *pt;
   if (thread == __get_tls()->tib_pthread) {
     return EDEADLK;
@@ -44,7 +46,9 @@ int pthread_join(pthread_t thread, void **value_ptr) {
       pt->status == kPosixThreadDetached) {
     return EINVAL;
   }
-  _pthread_wait(pt);
+  if ((rc = _pthread_wait(pt))) {
+    return rc;
+  }
   if (value_ptr) {
     *value_ptr = pt->rc;
   }
diff --git a/libc/thread/pthread_kill.c b/libc/thread/pthread_kill.c
index 61e39716d..615340b71 100644
--- a/libc/thread/pthread_kill.c
+++ b/libc/thread/pthread_kill.c
@@ -31,7 +31,7 @@
  * @raise EPERM if permission was denied
  * @asyncsignalsafe
  */
-int pthread_kill(pthread_t thread, int sig) {
+errno_t pthread_kill(pthread_t thread, int sig) {
   int rc, e = errno;
   struct PosixThread *pt = (struct PosixThread *)thread;
   if (!tkill(pt->tid, sig)) {
diff --git a/libc/thread/pthread_mutex_destroy.c b/libc/thread/pthread_mutex_destroy.c
index 87f4efa72..8199b6b81 100644
--- a/libc/thread/pthread_mutex_destroy.c
+++ b/libc/thread/pthread_mutex_destroy.c
@@ -25,7 +25,7 @@
  * @return 0 on success, or error number on failure
  * @raise EINVAL if mutex is locked in our implementation
  */
-int pthread_mutex_destroy(pthread_mutex_t *mutex) {
+errno_t pthread_mutex_destroy(pthread_mutex_t *mutex) {
   memset(mutex, -1, sizeof(*mutex));
   return 0;
 }
diff --git a/libc/thread/pthread_mutexattr_destroy.c b/libc/thread/pthread_mutexattr_destroy.c
index 49df496c1..6405b9144 100644
--- a/libc/thread/pthread_mutexattr_destroy.c
+++ b/libc/thread/pthread_mutexattr_destroy.c
@@ -16,14 +16,14 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/thread/thread.h"
 #include "libc/str/str.h"
+#include "libc/thread/thread.h"
 
 /**
  * Destroys mutex attr.
  * @return 0 on success, or error number on failure
  */
-int pthread_mutexattr_destroy(pthread_mutexattr_t *attr) {
+errno_t pthread_mutexattr_destroy(pthread_mutexattr_t *attr) {
   memset(attr, -1, sizeof(*attr));
   return 0;
 }
diff --git a/libc/thread/pthread_mutexattr_getpshared.c b/libc/thread/pthread_mutexattr_getpshared.c
index c521b91ce..fff1450a2 100644
--- a/libc/thread/pthread_mutexattr_getpshared.c
+++ b/libc/thread/pthread_mutexattr_getpshared.c
@@ -26,8 +26,8 @@
  *     - `PTHREAD_PROCESS_SHARED`
  * @return 0 on success, or error on failure
  */
-int pthread_mutexattr_getpshared(const pthread_mutexattr_t *attr,
-                                 int *pshared) {
+errno_t pthread_mutexattr_getpshared(const pthread_mutexattr_t *attr,
+                                     int *pshared) {
   *pshared = attr->_pshared;
   return 0;
 }
diff --git a/libc/thread/pthread_mutexattr_gettype.c b/libc/thread/pthread_mutexattr_gettype.c
index 5d1e9a8d7..117c10b63 100644
--- a/libc/thread/pthread_mutexattr_gettype.c
+++ b/libc/thread/pthread_mutexattr_gettype.c
@@ -27,7 +27,7 @@
  *     - `PTHREAD_MUTEX_ERRORCHECK`
  * @return 0 on success, or error on failure
  */
-int pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *type) {
+errno_t pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *type) {
   *type = attr->_type;
   return 0;
 }
diff --git a/libc/thread/pthread_mutexattr_init.c b/libc/thread/pthread_mutexattr_init.c
index a12bec7d8..115420480 100644
--- a/libc/thread/pthread_mutexattr_init.c
+++ b/libc/thread/pthread_mutexattr_init.c
@@ -22,7 +22,7 @@
  * Initializes mutex attr.
  * @return 0 on success, or error number on failure
  */
-int pthread_mutexattr_init(pthread_mutexattr_t *attr) {
+errno_t pthread_mutexattr_init(pthread_mutexattr_t *attr) {
   *attr = (pthread_mutexattr_t){0};
   return 0;
 }
diff --git a/libc/thread/pthread_mutexattr_setpshared.c b/libc/thread/pthread_mutexattr_setpshared.c
index c575cbd95..062bcdffc 100644
--- a/libc/thread/pthread_mutexattr_setpshared.c
+++ b/libc/thread/pthread_mutexattr_setpshared.c
@@ -28,7 +28,7 @@
  * @return 0 on success, or error on failure
  * @raises EINVAL if `pshared` is invalid
  */
-int pthread_mutexattr_setpshared(pthread_mutexattr_t *attr, int pshared) {
+errno_t pthread_mutexattr_setpshared(pthread_mutexattr_t *attr, int pshared) {
   switch (pshared) {
     case PTHREAD_PROCESS_SHARED:
     case PTHREAD_PROCESS_PRIVATE:
diff --git a/libc/thread/pthread_mutexattr_settype.c b/libc/thread/pthread_mutexattr_settype.c
index 766a4b7a4..2e5cdfe10 100644
--- a/libc/thread/pthread_mutexattr_settype.c
+++ b/libc/thread/pthread_mutexattr_settype.c
@@ -30,7 +30,7 @@
  * @return 0 on success, or error on failure
  * @raises EINVAL if `type` is invalid
  */
-int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type) {
+errno_t pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type) {
   switch (type) {
     case PTHREAD_MUTEX_NORMAL:
     case PTHREAD_MUTEX_RECURSIVE:
diff --git a/libc/thread/pthread_reschedule.c b/libc/thread/pthread_reschedule.c
index 1319a7dc2..4aca1c16e 100644
--- a/libc/thread/pthread_reschedule.c
+++ b/libc/thread/pthread_reschedule.c
@@ -23,7 +23,7 @@
 #include "libc/sysv/errfuns.h"
 #include "libc/thread/posixthread.internal.h"
 
-int _pthread_reschedule(struct PosixThread *pt) {
+errno_t _pthread_reschedule(struct PosixThread *pt) {
   int rc, e = errno;
   int policy = pt->attr.__schedpolicy;
   struct sched_param param = {pt->attr.__schedparam};
diff --git a/libc/thread/pthread_rwlock_destroy.c b/libc/thread/pthread_rwlock_destroy.c
index 47bc63c10..2e5d2bb60 100644
--- a/libc/thread/pthread_rwlock_destroy.c
+++ b/libc/thread/pthread_rwlock_destroy.c
@@ -25,7 +25,7 @@
  * @return 0 on success, or error number on failure
  * @raise EINVAL if any threads still hold the lock
  */
-int pthread_rwlock_destroy(pthread_rwlock_t *rwlock) {
+errno_t pthread_rwlock_destroy(pthread_rwlock_t *rwlock) {
   memset(rwlock, -1, sizeof(*rwlock));
   return 0;
 }
diff --git a/libc/thread/pthread_rwlock_init.c b/libc/thread/pthread_rwlock_init.c
index c9790a9b7..313daca38 100644
--- a/libc/thread/pthread_rwlock_init.c
+++ b/libc/thread/pthread_rwlock_init.c
@@ -24,8 +24,8 @@
  * @param attr may be null
  * @return 0 on success, or error number on failure
  */
-int pthread_rwlock_init(pthread_rwlock_t *rwlock,
-                        const pthread_rwlockattr_t *attr) {
+errno_t pthread_rwlock_init(pthread_rwlock_t *rwlock,
+                            const pthread_rwlockattr_t *attr) {
   *rwlock = (pthread_rwlock_t){0};
   return 0;
 }
diff --git a/libc/thread/pthread_rwlockattr_destroy.c b/libc/thread/pthread_rwlockattr_destroy.c
index 624b5fb5d..853f973dd 100644
--- a/libc/thread/pthread_rwlockattr_destroy.c
+++ b/libc/thread/pthread_rwlockattr_destroy.c
@@ -16,15 +16,15 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/thread/thread.h"
 #include "libc/str/str.h"
+#include "libc/thread/thread.h"
 
 /**
  * Destroys read-write lock attributes.
  *
  * @return 0 on success, or error on failure
  */
-int pthread_rwlockattr_destroy(pthread_rwlockattr_t *attr) {
+errno_t pthread_rwlockattr_destroy(pthread_rwlockattr_t *attr) {
   memset(attr, -1, sizeof(*attr));
   return 0;
 }
diff --git a/libc/thread/pthread_rwlockattr_getpshared.c b/libc/thread/pthread_rwlockattr_getpshared.c
index efafcb927..afcb140fd 100644
--- a/libc/thread/pthread_rwlockattr_getpshared.c
+++ b/libc/thread/pthread_rwlockattr_getpshared.c
@@ -26,8 +26,8 @@
  *     - `PTHREAD_PROCESS_SHARED` (unsupported)
  * @return 0 on success, or error on failure
  */
-int pthread_rwlockattr_getpshared(const pthread_rwlockattr_t *attr,
-                                  int *pshared) {
+errno_t pthread_rwlockattr_getpshared(const pthread_rwlockattr_t *attr,
+                                      int *pshared) {
   *pshared = *attr;
   return 0;
 }
diff --git a/libc/thread/pthread_rwlockattr_init.c b/libc/thread/pthread_rwlockattr_init.c
index dee6fb305..01807d180 100644
--- a/libc/thread/pthread_rwlockattr_init.c
+++ b/libc/thread/pthread_rwlockattr_init.c
@@ -23,7 +23,7 @@
  *
  * @return 0 on success, or error on failure
  */
-int pthread_rwlockattr_init(pthread_rwlockattr_t *attr) {
+errno_t pthread_rwlockattr_init(pthread_rwlockattr_t *attr) {
   *attr = 0;
   return 0;
 }
diff --git a/libc/thread/pthread_rwlockattr_setpshared.c b/libc/thread/pthread_rwlockattr_setpshared.c
index 5904c4d6c..e634edcc9 100644
--- a/libc/thread/pthread_rwlockattr_setpshared.c
+++ b/libc/thread/pthread_rwlockattr_setpshared.c
@@ -28,7 +28,7 @@
  * @return 0 on success, or error on failure
  * @raises EINVAL if `pshared` is invalid
  */
-int pthread_rwlockattr_setpshared(pthread_rwlockattr_t *attr, int pshared) {
+errno_t pthread_rwlockattr_setpshared(pthread_rwlockattr_t *attr, int pshared) {
   switch (pshared) {
     case PTHREAD_PROCESS_PRIVATE:
       *attr = pshared;
diff --git a/libc/thread/pthread_setcanceltype.c b/libc/thread/pthread_setcanceltype.c
index 65c7d7f2a..b61b8fcfa 100644
--- a/libc/thread/pthread_setcanceltype.c
+++ b/libc/thread/pthread_setcanceltype.c
@@ -32,7 +32,7 @@
  * @raise EINVAL if `type` has bad value
  * @see pthread_cancel() for docs
  */
-int pthread_setcanceltype(int type, int *oldtype) {
+errno_t pthread_setcanceltype(int type, int *oldtype) {
   struct PosixThread *pt;
   switch (type) {
     case PTHREAD_CANCEL_DEFERRED:
diff --git a/libc/thread/pthread_setname_np.c b/libc/thread/pthread_setname_np.c
index 0d10ae7d7..3123dce94 100644
--- a/libc/thread/pthread_setname_np.c
+++ b/libc/thread/pthread_setname_np.c
@@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/blockcancel.internal.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/dce.h"
@@ -28,30 +29,7 @@
 #include "libc/sysv/consts/pr.h"
 #include "libc/thread/posixthread.internal.h"
 
-/**
- * Registers custom name of thread with system, e.g.
- *
- *     void *worker(void *arg) {
- *       pthread_setname_np(pthread_self(), "justine");
- *       pause();
- *       return 0;
- *     }
- *
- *     int main(int argc, char *argv[]) {
- *       pthread_t id;
- *       pthread_create(&id, 0, worker, 0);
- *       pthread_join(id, 0);
- *     }
- *
- * ProTip: The `htop` software is good at displaying thread names.
- *
- * @return 0 on success, or errno on error
- * @raise ERANGE if length of `name` exceeded system limit, in which
- *    case the name may have still been set with os using truncation
- * @raise ENOSYS on MacOS, Windows, and OpenBSD
- * @see pthread_getname_np()
- */
-errno_t pthread_setname_np(pthread_t thread, const char *name) {
+static errno_t pthread_setname_impl(pthread_t thread, const char *name) {
   char path[128], *p;
   int fd, rc, tid, len, e = errno;
 
@@ -113,3 +91,34 @@ errno_t pthread_setname_np(pthread_t thread, const char *name) {
     return ENOSYS;
   }
 }
+
+/**
+ * Registers custom name of thread with system, e.g.
+ *
+ *     void *worker(void *arg) {
+ *       pthread_setname_np(pthread_self(), "justine");
+ *       pause();
+ *       return 0;
+ *     }
+ *
+ *     int main(int argc, char *argv[]) {
+ *       pthread_t id;
+ *       pthread_create(&id, 0, worker, 0);
+ *       pthread_join(id, 0);
+ *     }
+ *
+ * ProTip: The `htop` software is good at displaying thread names.
+ *
+ * @return 0 on success, or errno on error
+ * @raise ERANGE if length of `name` exceeded system limit, in which
+ *    case the name may have still been set with os using truncation
+ * @raise ENOSYS on MacOS, Windows, and OpenBSD
+ * @see pthread_getname_np()
+ */
+errno_t pthread_setname_np(pthread_t thread, const char *name) {
+  errno_t rc;
+  BLOCK_CANCELLATIONS;
+  rc = pthread_setname_impl(thread, name);
+  ALLOW_CANCELLATIONS;
+  return rc;
+}
diff --git a/libc/thread/pthread_setschedparam.c b/libc/thread/pthread_setschedparam.c
index 7126ba710..7a5d36c13 100644
--- a/libc/thread/pthread_setschedparam.c
+++ b/libc/thread/pthread_setschedparam.c
@@ -41,8 +41,8 @@
  * @see sched_get_priority_max()
  * @see sched_setscheduler()
  */
-int pthread_setschedparam(pthread_t thread, int policy,
-                          const struct sched_param *param) {
+errno_t pthread_setschedparam(pthread_t thread, int policy,
+                              const struct sched_param *param) {
   struct PosixThread *pt = (struct PosixThread *)thread;
   if (!param) return EINVAL;
   pt->attr.__schedpolicy = policy;
diff --git a/libc/thread/pthread_setschedprio.c b/libc/thread/pthread_setschedprio.c
index 8bb96c24b..6763aedce 100644
--- a/libc/thread/pthread_setschedprio.c
+++ b/libc/thread/pthread_setschedprio.c
@@ -22,7 +22,7 @@
 /**
  * Sets scheduler parameter on thread.
  */
-int pthread_setschedprio(pthread_t thread, int prio) {
+errno_t pthread_setschedprio(pthread_t thread, int prio) {
   struct PosixThread *pt = (struct PosixThread *)thread;
   pt->attr.__schedparam = prio;
   return _pthread_reschedule(pt);
diff --git a/libc/thread/pthread_sigmask.c b/libc/thread/pthread_sigmask.c
index 03093c8dc..2d84d8094 100644
--- a/libc/thread/pthread_sigmask.c
+++ b/libc/thread/pthread_sigmask.c
@@ -25,7 +25,7 @@
  * @return 0 on success, or errno on error
  * @asyncsignalsafe
  */
-int pthread_sigmask(int how, const sigset_t *set, sigset_t *old) {
+errno_t pthread_sigmask(int how, const sigset_t *set, sigset_t *old) {
   int rc, e = errno;
   if (!sigprocmask(how, set, old)) {
     rc = 0;
diff --git a/libc/thread/pthread_zombies.c b/libc/thread/pthread_zombies.c
index 0fe40f220..8ae0e9c28 100644
--- a/libc/thread/pthread_zombies.c
+++ b/libc/thread/pthread_zombies.c
@@ -44,6 +44,7 @@ void _pthread_zombies_add(struct PosixThread *pt) {
 }
 
 static void _pthread_zombies_collect(struct Zombie *z) {
+  // TODO(jart): We need a trywait() op here to avoid cancellation.
   _pthread_wait(z->pt);
   _pthread_free(z->pt);
   free(z);
diff --git a/libc/thread/sem_open.c b/libc/thread/sem_open.c
index 16ddf0cf6..f235d026e 100644
--- a/libc/thread/sem_open.c
+++ b/libc/thread/sem_open.c
@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
+#include "libc/calls/blockcancel.internal.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/struct/stat.h"
 #include "libc/dce.h"
@@ -195,6 +196,7 @@ sem_t *sem_open(const char *name, int oflag, ...) {
   if (!(path = sem_path_np(name, pathbuf, sizeof(pathbuf)))) {
     return SEM_FAILED;
   }
+  BLOCK_CANCELLATIONS;
   sem_open_init();
   sem_open_lock();
   if ((s = sem_open_reopen(path))) {
@@ -233,6 +235,7 @@ sem_t *sem_open(const char *name, int oflag, ...) {
     sem = SEM_FAILED;
   }
   sem_open_unlock();
+  ALLOW_CANCELLATIONS;
   return sem;
 }
 
diff --git a/libc/thread/sem_timedwait.c b/libc/thread/sem_timedwait.c
index dd098c044..c57cf7ebb 100644
--- a/libc/thread/sem_timedwait.c
+++ b/libc/thread/sem_timedwait.c
@@ -24,6 +24,7 @@
 #include "libc/limits.h"
 #include "libc/sysv/errfuns.h"
 #include "libc/thread/semaphore.h"
+#include "libc/thread/thread.h"
 #include "third_party/nsync/futex.internal.h"
 
 static void sem_delay(int n) {
@@ -51,11 +52,18 @@ static struct timespec *sem_timeout(struct timespec *memory,
   }
 }
 
+static void sem_timedwait_cleanup(void *arg) {
+  sem_t *sem = arg;
+  _unassert(atomic_fetch_add_explicit(&sem->sem_waiters, -1,
+                                      memory_order_acq_rel) > 0);
+}
+
 /**
  * Locks semaphore w/ deadline.
  *
  * @param abstime is absolute deadline or null to wait forever
  * @return 0 on success, or -1 w/ errno
+ * @raise ECANCELED if calling thread was cancelled in masked mode
  * @raise EINTR if signal was delivered instead
  * @raise EDEADLK if deadlock was detected
  * @raise ETIMEDOUT if deadline expired
@@ -80,14 +88,16 @@ int sem_timedwait(sem_t *sem, const struct timespec *abstime) {
   }
 
   _unassert(atomic_fetch_add_explicit(&sem->sem_waiters, +1,
-                                      memory_order_acquire) >= 0);
+                                      memory_order_acq_rel) >= 0);
+  pthread_cleanup_push(sem_timedwait_cleanup, sem);
 
   do {
     if (!(v = atomic_load_explicit(&sem->sem_value, memory_order_relaxed))) {
       rc = nsync_futex_wait_(&sem->sem_value, v, sem->sem_pshared,
                              sem_timeout(&ts, abstime));
-      if (rc == -EINTR) {
-        rc = eintr();
+      if (rc == -EINTR || rc == -ECANCELED) {
+        errno = -rc;
+        rc = -1;
       } else if (rc == -EAGAIN || rc == -EWOULDBLOCK) {
         rc = 0;
       } else if (rc == -ETIMEDOUT) {
@@ -111,8 +121,7 @@ int sem_timedwait(sem_t *sem, const struct timespec *abstime) {
                              &sem->sem_value, &v, v - 1, memory_order_acquire,
                              memory_order_relaxed)));
 
-  _unassert(atomic_fetch_add_explicit(&sem->sem_waiters, -1,
-                                      memory_order_release) > 0);
+  pthread_cleanup_pop(1);
 
   return rc;
 }
diff --git a/libc/thread/sem_wait.c b/libc/thread/sem_wait.c
index e32b41ed3..90c2052ef 100644
--- a/libc/thread/sem_wait.c
+++ b/libc/thread/sem_wait.c
@@ -22,6 +22,7 @@
  * Locks semaphore.
  *
  * @return 0 on success, or -1 w/ errno
+ * @raise ECANCELED if calling thread was cancelled in masked mode
  * @raise EINTR if signal was delivered instead
  * @raise EDEADLK if deadlock was detected
  * @raise EINVAL if `sem` is invalid
diff --git a/libc/thread/wait0.c b/libc/thread/wait0.c
index f3ec6ea07..1d9d34ec2 100644
--- a/libc/thread/wait0.c
+++ b/libc/thread/wait0.c
@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/dce.h"
+#include "libc/errno.h"
 #include "libc/intrin/atomic.h"
 #include "libc/thread/wait0.internal.h"
 #include "third_party/nsync/futex.internal.h"
@@ -29,10 +30,16 @@
  * order to know when it's safe to free a thread's stack. This function
  * uses futexes on Linux, FreeBSD, OpenBSD, and Windows. On other
  * platforms this uses polling with exponential backoff.
+ *
+ * @return 0 on success, or errno on error
+ * @raise ECANCELED if calling thread was cancelled in masked mode
  */
-void _wait0(const atomic_int *ctid) {
-  int x;
+errno_t _wait0(const atomic_int *ctid) {
+  int x, rc;
   while ((x = atomic_load_explicit(ctid, memory_order_acquire))) {
-    nsync_futex_wait_(ctid, x, !IsWindows(), 0);
+    if (nsync_futex_wait_(ctid, x, !IsWindows(), 0) == -ECANCELED) {
+      return ECANCELED;
+    }
   }
+  return 0;
 }
diff --git a/libc/thread/wait0.internal.h b/libc/thread/wait0.internal.h
index ec89485a9..2aeaa7478 100644
--- a/libc/thread/wait0.internal.h
+++ b/libc/thread/wait0.internal.h
@@ -4,7 +4,7 @@
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 COSMOPOLITAN_C_START_
 
-void _wait0(const atomic_int *) hidden;
+errno_t _wait0(const atomic_int *) hidden;
 
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
diff --git a/net/turfwar/turfwar.c b/net/turfwar/turfwar.c
index 8a82e40ff..5947d8d44 100644
--- a/net/turfwar/turfwar.c
+++ b/net/turfwar/turfwar.c
@@ -24,6 +24,7 @@
 #include "libc/calls/struct/sigaction.h"
 #include "libc/calls/struct/sigset.h"
 #include "libc/calls/struct/stat.h"
+#include "libc/calls/struct/sysinfo.h"
 #include "libc/calls/struct/timespec.h"
 #include "libc/calls/struct/timeval.h"
 #include "libc/dce.h"
@@ -358,6 +359,13 @@ struct Claims {
   } data[QUEUE_MAX];
 } g_claims;
 
+long GetTotalRam(void) {
+  struct sysinfo si;
+  si.totalram = 256 * 1024 * 1024;
+  sysinfo(&si);
+  return si.totalram;
+}
+
 // easy string sender
 ssize_t Write(int fd, const char *s) {
   return write(fd, s, strlen(s));
@@ -397,8 +405,14 @@ bool CheckDb(const char *file, int line, int rc, sqlite3 *db) {
 // we need to do is wait a little bit, and use exponential backoff
 int DbOpen(const char *path, sqlite3 **db) {
   int i, rc;
+  char sql[128];
   rc = sqlite3_open(path, db);
   if (rc != SQLITE_OK) return rc;
+  if (!IsWindows() && !IsOpenbsd()) {
+    ksnprintf(sql, sizeof(sql), "PRAGMA mmap_size=%ld", GetTotalRam());
+    rc = sqlite3_exec(*db, sql, 0, 0, 0);
+    if (rc != SQLITE_OK) return rc;
+  }
   for (i = 0; i < 7; ++i) {
     rc = sqlite3_exec(*db, "PRAGMA journal_mode=WAL", 0, 0, 0);
     if (rc == SQLITE_OK) break;
@@ -410,6 +424,7 @@ int DbOpen(const char *path, sqlite3 **db) {
 
 // why not make the statement prepare api a little less hairy too
 int DbPrepare(sqlite3 *db, sqlite3_stmt **stmt, const char *sql) {
+  kprintf("%s\n", sql);
   return sqlite3_prepare_v2(db, sql, -1, stmt, 0);
 }
 
diff --git a/test/libc/calls/sigaction_test.c b/test/libc/calls/sigaction_test.c
index 86806b071..fb102d7bf 100644
--- a/test/libc/calls/sigaction_test.c
+++ b/test/libc/calls/sigaction_test.c
@@ -194,7 +194,7 @@ TEST(sigaction, autoZombieSlayer) {
   if (!pid) _Exit(0);
   ASSERT_SYS(0, pid, wait(0));
   // enable automatic zombie slayer
-  sa.sa_handler = SIG_IGN;
+  sa.sa_handler = SIG_DFL;     // POSIX.1 says no SIG_IGN
   sa.sa_flags = SA_NOCLDWAIT;  // seems to be optional
   sigemptyset(&sa.sa_mask);
   ASSERT_SYS(0, 0, sigaction(SIGCHLD, &sa, &sa));
diff --git a/test/libc/thread/pthread_cancel_test.c b/test/libc/thread/pthread_cancel_test.c
index 16eb3e0bf..e59f99e4c 100644
--- a/test/libc/thread/pthread_cancel_test.c
+++ b/test/libc/thread/pthread_cancel_test.c
@@ -24,8 +24,11 @@
 #include "libc/runtime/runtime.h"
 #include "libc/testlib/testlib.h"
 #include "libc/thread/thread.h"
+#include "libc/thread/thread2.h"
 
 int pfds[2];
+pthread_cond_t cv;
+pthread_mutex_t mu;
 atomic_bool gotcleanup;
 char testlib_enable_tmp_setup_teardown;
 
@@ -37,6 +40,49 @@ void OnCleanup(void *arg) {
   gotcleanup = true;
 }
 
+void *CancelSelfWorkerDeferred(void *arg) {
+  char buf[8];
+  pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, 0);
+  pthread_cleanup_push(OnCleanup, 0);
+  pthread_cancel(pthread_self());
+  read(pfds[0], buf, sizeof(buf));
+  pthread_cleanup_pop(0);
+  return 0;
+}
+
+TEST(pthread_cancel, self_deferred_waitsForCancellationPoint) {
+  void *rc;
+  pthread_t th;
+  ASSERT_SYS(0, 0, pipe(pfds));
+  ASSERT_EQ(0, pthread_create(&th, 0, CancelSelfWorkerDeferred, 0));
+  ASSERT_EQ(0, pthread_join(th, &rc));
+  ASSERT_EQ(PTHREAD_CANCELED, rc);
+  ASSERT_TRUE(gotcleanup);
+  ASSERT_SYS(0, 0, close(pfds[1]));
+  ASSERT_SYS(0, 0, close(pfds[0]));
+}
+
+void *CancelSelfWorkerAsync(void *arg) {
+  char buf[8];
+  pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, 0);
+  pthread_cleanup_push(OnCleanup, 0);
+  pthread_cancel(pthread_self());
+  pthread_cleanup_pop(0);
+  return 0;
+}
+
+TEST(pthread_cancel, self_asynchronous_takesImmediateEffect) {
+  void *rc;
+  pthread_t th;
+  ASSERT_SYS(0, 0, pipe(pfds));
+  ASSERT_EQ(0, pthread_create(&th, 0, CancelSelfWorkerAsync, 0));
+  ASSERT_EQ(0, pthread_join(th, &rc));
+  ASSERT_EQ(PTHREAD_CANCELED, rc);
+  ASSERT_TRUE(gotcleanup);
+  ASSERT_SYS(0, 0, close(pfds[1]));
+  ASSERT_SYS(0, 0, close(pfds[0]));
+}
+
 void *Worker(void *arg) {
   int n;
   char buf[8];
@@ -74,7 +120,6 @@ TEST(pthread_cancel, synchronous_delayed) {
 }
 
 void *DisabledWorker(void *arg) {
-  int n;
   char buf[8];
   pthread_setcancelstate(PTHREAD_CANCEL_MASKED, 0);
   pthread_cleanup_push(OnCleanup, 0);
@@ -109,3 +154,61 @@ TEST(pthread_cancel, masked_delayed) {
   ASSERT_SYS(0, 0, close(pfds[1]));
   ASSERT_SYS(0, 0, close(pfds[0]));
 }
+
+void *CondWaitMaskedWorker(void *arg) {
+  pthread_setcancelstate(PTHREAD_CANCEL_MASKED, 0);
+  ASSERT_EQ(0, pthread_mutex_lock(&mu));
+  ASSERT_EQ(ECANCELED, pthread_cond_timedwait(&cv, &mu, 0));
+  ASSERT_EQ(0, pthread_mutex_unlock(&mu));
+  return 0;
+}
+
+TEST(pthread_cancel, condMaskedWait) {
+  void *rc;
+  pthread_t th;
+  ASSERT_EQ(0, pthread_create(&th, 0, CondWaitMaskedWorker, 0));
+  ASSERT_EQ(0, pthread_cancel(th));
+  ASSERT_EQ(0, pthread_join(th, &rc));
+  ASSERT_EQ(0, rc);
+}
+
+TEST(pthread_cancel, condWaitMaskedDelayed) {
+  void *rc;
+  pthread_t th;
+  ASSERT_EQ(0, pthread_create(&th, 0, CondWaitMaskedWorker, 0));
+  usleep(10);
+  ASSERT_EQ(0, pthread_cancel(th));
+  ASSERT_EQ(0, pthread_join(th, &rc));
+  ASSERT_EQ(0, rc);
+}
+
+void *CondWaitDeferredWorker(void *arg) {
+  pthread_setcancelstate(PTHREAD_CANCEL_DEFERRED, 0);
+  ASSERT_EQ(0, pthread_mutex_lock(&mu));
+  ASSERT_EQ(ECANCELED, pthread_cond_timedwait(&cv, &mu, 0));
+  ASSERT_EQ(0, pthread_mutex_unlock(&mu));
+  return 0;
+}
+
+TEST(pthread_cancel, condDeferredWait) {
+  void *rc;
+  pthread_t th;
+  ASSERT_EQ(0, pthread_create(&th, 0, CondWaitDeferredWorker, 0));
+  ASSERT_EQ(0, pthread_cancel(th));
+  ASSERT_EQ(0, pthread_join(th, &rc));
+  ASSERT_EQ(PTHREAD_CANCELED, rc);
+  ASSERT_EQ(0, pthread_mutex_trylock(&mu));
+  ASSERT_EQ(0, pthread_mutex_unlock(&mu));
+}
+
+TEST(pthread_cancel, condDeferredWaitDelayed) {
+  void *rc;
+  pthread_t th;
+  ASSERT_EQ(0, pthread_create(&th, 0, CondWaitDeferredWorker, 0));
+  usleep(10);
+  ASSERT_EQ(0, pthread_cancel(th));
+  ASSERT_EQ(0, pthread_join(th, &rc));
+  ASSERT_EQ(PTHREAD_CANCELED, rc);
+  ASSERT_EQ(0, pthread_mutex_trylock(&mu));
+  ASSERT_EQ(0, pthread_mutex_unlock(&mu));
+}
diff --git a/third_party/musl/grp.c b/third_party/musl/grp.c
index d97a2e293..9a1e92699 100644
--- a/third_party/musl/grp.c
+++ b/third_party/musl/grp.c
@@ -30,6 +30,7 @@
 #include "libc/mem/mem.h"
 #include "libc/stdio/stdio.h"
 #include "libc/str/str.h"
+#include "libc/thread/thread.h"
 #include "third_party/musl/passwd.h"
 
 asm(".ident\t\"\\n\\n\
@@ -37,9 +38,6 @@ Musl libc (MIT License)\\n\
 Copyright 2005-2014 Rich Felker, et. al.\"");
 asm(".include \"libc/disclaimer.inc\"");
 
-#define PTHREAD_CANCEL_DISABLE       0
-#define pthread_setcancelstate(x, y) (void)y
-
 static unsigned atou(char **s) {
   unsigned x;
   for (x = 0; **s - '0' < 10U; ++*s) x = 10 * x + (**s - '0');
diff --git a/third_party/musl/nftw.c b/third_party/musl/nftw.c
index 159a3144c..48145e705 100644
--- a/third_party/musl/nftw.c
+++ b/third_party/musl/nftw.c
@@ -32,6 +32,7 @@
 #include "libc/str/str.h"
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/consts/s.h"
+#include "libc/thread/thread.h"
 #include "third_party/musl/ftw.h"
 
 asm(".ident\t\"\\n\\n\
@@ -44,9 +45,6 @@ asm(".include \"libc/disclaimer.inc\"");
    should be changed to use realloc */
 #define PATH_MAX2 2048
 
-/* no cosmo pthreads support atm */
-#define pthread_setcancelstate(...)
-
 /* clang-format off */
 
 struct history
diff --git a/third_party/musl/pwd.c b/third_party/musl/pwd.c
index b56aafa25..67ad73658 100644
--- a/third_party/musl/pwd.c
+++ b/third_party/musl/pwd.c
@@ -30,6 +30,7 @@
 #include "libc/mem/mem.h"
 #include "libc/stdio/stdio.h"
 #include "libc/str/str.h"
+#include "libc/thread/thread.h"
 #include "third_party/musl/passwd.h"
 
 asm(".ident\t\"\\n\\n\
@@ -38,9 +39,6 @@ Copyright 2005-2014 Rich Felker, et. al.\"");
 asm(".include \"libc/disclaimer.inc\"");
 /* clang-format off */
 
-#define PTHREAD_CANCEL_DISABLE       0
-#define pthread_setcancelstate(x, y) (void)y
-
 static unsigned
 atou(char **s)
 {
diff --git a/third_party/nsync/README.cosmo b/third_party/nsync/README.cosmo
index 2ebdf744b..159da96ef 100644
--- a/third_party/nsync/README.cosmo
+++ b/third_party/nsync/README.cosmo
@@ -17,3 +17,4 @@ LOCAL CHANGES
 
   - nsync_malloc_() is implemented as kmalloc()
   - nsync_mu_semaphore uses Cosmopolitan Futexes
+  - block pthread cancellations in nsync_mu_lock_slow_
diff --git a/third_party/nsync/futex.c b/third_party/nsync/futex.c
index 8f5c5c0b0..c69504e9c 100644
--- a/third_party/nsync/futex.c
+++ b/third_party/nsync/futex.c
@@ -23,17 +23,20 @@
 #include "libc/calls/state.internal.h"
 #include "libc/calls/struct/timespec.h"
 #include "libc/calls/struct/timespec.internal.h"
+#include "libc/calls/syscall_support-nt.internal.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/intrin/atomic.h"
 #include "libc/intrin/describeflags.internal.h"
 #include "libc/intrin/strace.internal.h"
+#include "libc/intrin/weaken.h"
 #include "libc/limits.h"
 #include "libc/nt/runtime.h"
 #include "libc/nt/synchronization.h"
 #include "libc/sysv/consts/clock.h"
 #include "libc/sysv/consts/futex.h"
 #include "libc/sysv/consts/timer.h"
+#include "libc/sysv/errfuns.h"
 #include "libc/thread/freebsd.internal.h"
 #include "libc/thread/thread.h"
 #include "libc/thread/tls.h"
@@ -45,7 +48,9 @@
 
 #define FUTEX_WAIT_BITS_ FUTEX_BITSET_MATCH_ANY
 
-int _futex (atomic_int *, int, int, const struct timespec *, int *, int);
+errno_t _futex (atomic_int *, int, int, const struct timespec *, int *, int);
+errno_t _futex_wake (atomic_int *, int, int) asm ("_futex");
+int sys_futex_cp (atomic_int *, int, int, const struct timespec *, int *, int);
 
 static int FUTEX_WAIT_;
 static int FUTEX_PRIVATE_FLAG_;
@@ -59,6 +64,7 @@ __attribute__((__constructor__)) static void nsync_futex_init_ (void) {
 
 	if (IsWindows ()) {
 		FUTEX_IS_SUPPORTED = true;
+		FUTEX_TIMEOUT_IS_ABSOLUTE = true;
 		return;
 	}
 
@@ -70,8 +76,6 @@ __attribute__((__constructor__)) static void nsync_futex_init_ (void) {
 	}
 
         if (!(FUTEX_IS_SUPPORTED = IsLinux () || IsOpenbsd ())) {
-		// we're using sched_yield() so let's
-		// avoid needless clock_gettime calls
 		FUTEX_TIMEOUT_IS_ABSOLUTE = true;
 		return;
 	}
@@ -101,7 +105,7 @@ __attribute__((__constructor__)) static void nsync_futex_init_ (void) {
 		FUTEX_TIMEOUT_IS_ABSOLUTE = true;
 	} else if (IsOpenbsd () ||
 		   (!IsTiny () && IsLinux () &&
-		    !_futex (&x, FUTEX_WAKE_PRIVATE, 1, 0, 0, 0))) {
+		    !_futex_wake (&x, FUTEX_WAKE_PRIVATE, 1))) {
 		FUTEX_WAIT_ = FUTEX_WAIT;
 		FUTEX_PRIVATE_FLAG_ = FUTEX_PRIVATE_FLAG;
 	} else {
@@ -110,13 +114,10 @@ __attribute__((__constructor__)) static void nsync_futex_init_ (void) {
 }
 
 static int nsync_futex_polyfill_ (atomic_int *w, int expect, struct timespec *timeout) {
+	int rc;
 	int64_t nanos, maxnanos;
 	struct timespec ts, deadline;
 
-	if (atomic_load_explicit (w, memory_order_relaxed) != expect) {
-		return -EAGAIN;
-	}
-
 	ts = nsync_time_now ();
 	if (!timeout) {
 		deadline = nsync_time_no_deadline;
@@ -129,15 +130,15 @@ static int nsync_futex_polyfill_ (atomic_int *w, int expect, struct timespec *ti
 	nanos = 100;
 	maxnanos = __SIG_POLLING_INTERVAL_MS * 1000L * 1000;
 	while (nsync_time_cmp (deadline, ts) > 0) {
-		if (atomic_load_explicit (w, memory_order_relaxed) != expect) {
-			return 0;
-		}
 		ts = nsync_time_add (ts, _timespec_fromnanos (nanos));
 		if (nsync_time_cmp (ts, deadline) > 0) {
 			ts = deadline;
 		}
-		if (nsync_time_sleep_until (ts)) {
-			return -EINTR;
+		if (atomic_load_explicit (w, memory_order_acquire) != expect) {
+			return 0;
+		}
+		if ((rc = nsync_time_sleep_until (ts))) {
+			return -rc;
 		}
 		if (nanos < maxnanos) {
 			nanos <<= 1;
@@ -150,10 +151,46 @@ static int nsync_futex_polyfill_ (atomic_int *w, int expect, struct timespec *ti
 	return -ETIMEDOUT;
 }
 
-int nsync_futex_wait_ (atomic_int *w, int expect, char pshare, struct timespec *timeout) {
+static int nsync_futex_wait_win32_ (atomic_int *w, int expect, char pshare, struct timespec *timeout) {
+	int rc;
 	uint32_t ms;
+	struct timespec deadline, interval, remain, wait, now;
+
+	if (timeout) {
+		deadline = *timeout;
+	} else {
+		deadline = nsync_time_no_deadline;
+	}
+
+	while (!(rc = _check_interrupts (false, 0))) {
+		now = nsync_time_now ();
+		if (nsync_time_cmp (now, deadline) > 0) {
+			rc = etimedout();
+			break;
+		}
+		remain = nsync_time_sub (deadline, now);
+		interval = _timespec_frommillis (__SIG_POLLING_INTERVAL_MS);
+		wait = nsync_time_cmp (remain, interval) > 0 ? interval : remain;
+		if (atomic_load_explicit (w, memory_order_acquire) != expect) {
+			break;
+		}
+		if (WaitOnAddress (w, &expect, sizeof(int), _timespec_tomillis (wait))) {
+			break;
+		} else {
+			ASSERT (GetLastError () == ETIMEDOUT);
+		}
+	}
+
+	return rc;
+}
+
+int nsync_futex_wait_ (atomic_int *w, int expect, char pshare, struct timespec *timeout) {
 	int e, rc, op, fop;
 
+	if (atomic_load_explicit (w, memory_order_acquire) != expect) {
+		return -EAGAIN;
+	}
+
 	op = FUTEX_WAIT_;
 	if (pshare == PTHREAD_PROCESS_PRIVATE) {
 		op |= FUTEX_PRIVATE_FLAG_;
@@ -165,37 +202,35 @@ int nsync_futex_wait_ (atomic_int *w, int expect, char pshare, struct timespec *
 		   DescribeTimespec (0, timeout));
 
 	if (FUTEX_IS_SUPPORTED) {
+		e = errno;
 		if (IsWindows ()) {
 			// Windows 8 futexes don't support multiple processes :(
-			if (pshare) {
-				goto Polyfill;
-			}
-			e = errno;
-			if (_check_interrupts (false, 0)) {
-				rc = -errno;
-				errno = e;
-			} else {
-				if (timeout) {
-					ms = _timespec_tomillis (*timeout);
-				} else {
-					ms = -1;
-				}
-				if (WaitOnAddress (w, &expect, sizeof(int), ms)) {
-					rc = 0;
-				} else {
-					rc = -GetLastError ();
-				}
-			}
+			if (pshare) goto Polyfill;
+			rc = nsync_futex_wait_win32_ (w, expect, pshare, timeout);
 		} else if (IsFreebsd ()) {
-			rc = sys_umtx_timedwait_uint (
-				w, expect, pshare, timeout);
+			rc = sys_umtx_timedwait_uint (w, expect, pshare, timeout);
 		} else {
-			rc = _futex (w, op, expect, timeout, 0,
-				     FUTEX_WAIT_BITS_);
+			rc = sys_futex_cp (w, op, expect, timeout, 0, FUTEX_WAIT_BITS_);
 			if (IsOpenbsd() && rc > 0) {
-				rc = -rc;
+				// OpenBSD futex() returns errors as
+				// positive numbers without setting the
+				// carry flag. It's an irregular miracle
+				// because OpenBSD returns ECANCELED if
+				// futex() is interrupted w/ SA_RESTART
+				// so we're able to tell it apart from
+				// PT_MASKED which causes the wrapper
+				// to put ECANCELED into errno.
+				if (rc == ECANCELED) {
+					rc = EINTR;
+				}
+				errno = rc;
+				rc = -1;
 			}
 		}
+		if (rc == -1) {
+			rc = -errno;
+			errno = e;
+		}
 	} else {
 	Polyfill:
 		__get_tls()->tib_flags |= TIB_FLAG_TIME_CRITICAL;
@@ -214,7 +249,6 @@ int nsync_futex_wait_ (atomic_int *w, int expect, char pshare, struct timespec *
 
 int nsync_futex_wake_ (atomic_int *w, int count, char pshare) {
 	int e, rc, op, fop;
-	int wake (atomic_int *, int, int) asm ("_futex");
 
 	ASSERT (count == 1 || count == INT_MAX);
 
@@ -240,9 +274,9 @@ int nsync_futex_wake_ (atomic_int *w, int count, char pshare) {
 			} else {
 				fop = UMTX_OP_WAKE_PRIVATE;
 			}
-			rc = sys_umtx_op (w, fop, count, 0, 0);
+			rc = _futex_wake (w, fop, count);
 		} else {
-			rc = wake (w, op, count);
+			rc = _futex_wake (w, op, count);
 		}
 	} else {
 	Polyfill:
diff --git a/third_party/nsync/mem/nsync_cv.c b/third_party/nsync/mem/nsync_cv.c
index 7e2cf1428..fb42829b4 100644
--- a/third_party/nsync/mem/nsync_cv.c
+++ b/third_party/nsync/mem/nsync_cv.c
@@ -16,6 +16,7 @@
 │ limitations under the License.                                               │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/str/str.h"
+#include "libc/thread/thread.h"
 #include "third_party/nsync/atomic.internal.h"
 #include "third_party/nsync/common.internal.h"
 #include "third_party/nsync/cv.h"
@@ -202,6 +203,7 @@ int nsync_cv_wait_with_deadline_generic (nsync_cv *pcv, void *pmu,
 	waiter *w;
 	IGNORE_RACES_START ();
 	w = nsync_waiter_new_ ();
+	pthread_cleanup_push((void *)nsync_waiter_free_, w);
 	ATM_STORE (&w->nw.waiting, 1);
 	w->cond.f = NULL; /* Not using a conditional critical section. */
 	w->cond.v = NULL;
@@ -312,6 +314,7 @@ int nsync_cv_wait_with_deadline_generic (nsync_cv *pcv, void *pmu,
 			(*lock) (pmu);
 		}
 	}
+	pthread_cleanup_pop(0);
 	IGNORE_RACES_END ();
 	return (outcome);
 }
diff --git a/third_party/nsync/mem/nsync_mu_wait.c b/third_party/nsync/mem/nsync_mu_wait.c
index 9b409e239..693839fbe 100644
--- a/third_party/nsync/mem/nsync_mu_wait.c
+++ b/third_party/nsync/mem/nsync_mu_wait.c
@@ -15,6 +15,7 @@
 │ See the License for the specific language governing permissions and          │
 │ limitations under the License.                                               │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/blockcancel.internal.h"
 #include "third_party/nsync/atomic.h"
 #include "third_party/nsync/common.internal.h"
 #include "third_party/nsync/dll.h"
@@ -153,6 +154,7 @@ int nsync_mu_wait_with_deadline (nsync_mu *mu,
 	/* Work out in which mode the lock is held. */
 	uint32_t old_word;
 	IGNORE_RACES_START ();
+	BLOCK_CANCELLATIONS; /* not supported yet */
 	old_word = ATM_LOAD (&mu->word);
 	if ((old_word & MU_ANY_LOCK) == 0) {
 		nsync_panic_ ("nsync_mu not held in some mode when calling "
@@ -265,6 +267,7 @@ int nsync_mu_wait_with_deadline (nsync_mu *mu,
 	if (condition_is_true) {
 		outcome = 0; /* condition is true trumps other outcomes. */
 	}
+	ALLOW_CANCELLATIONS;
 	IGNORE_RACES_END ();
 	return (outcome);
 }
diff --git a/third_party/nsync/mem/nsync_wait.c b/third_party/nsync/mem/nsync_wait.c
index de75ab165..71cffaece 100644
--- a/third_party/nsync/mem/nsync_wait.c
+++ b/third_party/nsync/mem/nsync_wait.c
@@ -15,6 +15,7 @@
 │ See the License for the specific language governing permissions and          │
 │ limitations under the License.                                               │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/blockcancel.internal.h"
 #include "libc/mem/mem.h"
 #include "third_party/nsync/atomic.h"
 #include "third_party/nsync/atomic.internal.h"
@@ -36,6 +37,7 @@ int nsync_wait_n (void *mu, void (*lock) (void *), void (*unlock) (void *),
 		  int count, struct nsync_waitable_s *waitable[]) {
 	int ready;
 	IGNORE_RACES_START ();
+	BLOCK_CANCELLATIONS;  /* TODO(jart): Does this need pthread cancellations? */
 	for (ready = 0; ready != count &&
 			nsync_time_cmp ((*waitable[ready]->funcs->ready_time) (
 						waitable[ready]->v, NULL),
@@ -102,6 +104,7 @@ int nsync_wait_n (void *mu, void (*lock) (void *), void (*unlock) (void *),
 			(*lock) (mu);
 		}
 	}
+	ALLOW_CANCELLATIONS;
 	IGNORE_RACES_END ();
 	return (ready);
 }
diff --git a/third_party/nsync/mu.c b/third_party/nsync/mu.c
index bda08494d..28fd8d7a8 100644
--- a/third_party/nsync/mu.c
+++ b/third_party/nsync/mu.c
@@ -15,6 +15,7 @@
 │ See the License for the specific language governing permissions and          │
 │ limitations under the License.                                               │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/blockcancel.internal.h"
 #include "libc/str/str.h"
 #include "third_party/nsync/atomic.h"
 #include "third_party/nsync/common.internal.h"
@@ -52,6 +53,7 @@ void nsync_mu_lock_slow_ (nsync_mu *mu, waiter *w, uint32_t clear, lock_type *l_
 	uint32_t wait_count;
 	uint32_t long_wait;
 	unsigned attempts = 0; /* attempt count; used for spinloop backoff */
+	BLOCK_CANCELLATIONS;
 	w->cv_mu = NULL;      /* not a cv wait */
 	w->cond.f = NULL; /* Not using a conditional critical section. */
 	w->cond.v = NULL;
@@ -72,7 +74,7 @@ void nsync_mu_lock_slow_ (nsync_mu *mu, waiter *w, uint32_t clear, lock_type *l_
 			if (ATM_CAS_ACQ (&mu->word, old_word,
 					 (old_word+l_type->add_to_acquire) &
 					  ~(clear|long_wait|l_type->clear_on_acquire))) {
-				return;
+				break;
 			}
 		} else if ((old_word&MU_SPINLOCK) == 0 &&
 			   ATM_CAS_ACQ (&mu->word, old_word,
@@ -126,6 +128,7 @@ void nsync_mu_lock_slow_ (nsync_mu *mu, waiter *w, uint32_t clear, lock_type *l_
 		}
 		attempts = nsync_spin_delay_ (attempts);
 	}
+	ALLOW_CANCELLATIONS;
 }
 
 /* Attempt to acquire *mu in writer mode without blocking, and return non-zero
diff --git a/third_party/nsync/mu_semaphore.c b/third_party/nsync/mu_semaphore.c
index a43b04432..8a903c5b6 100644
--- a/third_party/nsync/mu_semaphore.c
+++ b/third_party/nsync/mu_semaphore.c
@@ -17,6 +17,8 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
 #include "libc/errno.h"
+#include "libc/intrin/kprintf.h"
+#include "libc/intrin/weaken.h"
 #include "libc/str/str.h"
 #include "libc/thread/thread.h"
 #include "third_party/nsync/atomic.h"
@@ -51,25 +53,32 @@ void nsync_mu_semaphore_init (nsync_semaphore *s) {
 }
 
 /* Wait until the count of *s exceeds 0, and decrement it. */
-void nsync_mu_semaphore_p (nsync_semaphore *s) {
+errno_t nsync_mu_semaphore_p (nsync_semaphore *s) {
 	struct futex *f = (struct futex *) s;
 	int i;
+	int result = 0;
 	do {
 		i = ATM_LOAD ((nsync_atomic_uint32_ *) &f->i);
 		if (i == 0) {
-			int futex_result = nsync_futex_wait_ ((atomic_int *)&f->i, i, PTHREAD_PROCESS_PRIVATE, NULL);
+			int futex_result = nsync_futex_wait_ (
+				(atomic_int *)&f->i, i, PTHREAD_PROCESS_PRIVATE, NULL);
 			ASSERT (futex_result == 0 ||
 				futex_result == -EINTR ||
 				futex_result == -EAGAIN ||
+				futex_result == -ECANCELED ||
 				futex_result == -EWOULDBLOCK);
+			if (futex_result == -ECANCELED) {
+				result = ECANCELED;
+			}
 		}
-	} while (i == 0 || !ATM_CAS_ACQ ((nsync_atomic_uint32_ *) &f->i, i, i-1));
+	} while (result == 0 && (i == 0 || !ATM_CAS_ACQ ((nsync_atomic_uint32_ *) &f->i, i, i-1)));
+	return result;
 }
 
 /* Wait until one of:
    the count of *s is non-zero, in which case decrement *s and return 0;
    or abs_deadline expires, in which case return ETIMEDOUT. */
-int nsync_mu_semaphore_p_with_deadline (nsync_semaphore *s, nsync_time abs_deadline) {
+errno_t nsync_mu_semaphore_p_with_deadline (nsync_semaphore *s, nsync_time abs_deadline) {
 	struct futex *f = (struct futex *)s;
 	int i;
 	int result = 0;
@@ -103,6 +112,7 @@ int nsync_mu_semaphore_p_with_deadline (nsync_semaphore *s, nsync_time abs_deadl
 			ASSERT (futex_result == 0 ||
 				futex_result == -EINTR ||
 				futex_result == -EAGAIN ||
+				futex_result == -ECANCELED ||
 				futex_result == -ETIMEDOUT ||
 				futex_result == -EWOULDBLOCK);
 			/* Some systems don't wait as long as they are told. */ 
@@ -110,6 +120,9 @@ int nsync_mu_semaphore_p_with_deadline (nsync_semaphore *s, nsync_time abs_deadl
 			    nsync_time_cmp (abs_deadline, nsync_time_now ()) <= 0) {
 				result = ETIMEDOUT;
 			}
+			if (futex_result == -ECANCELED) {
+				result = ECANCELED;
+			}
 		}
 	} while (result == 0 && (i == 0 || !ATM_CAS_ACQ ((nsync_atomic_uint32_ *) &f->i, i, i - 1)));
 	return (result);
diff --git a/third_party/nsync/mu_semaphore.h b/third_party/nsync/mu_semaphore.h
index 3cf252808..a2c9c6b45 100644
--- a/third_party/nsync/mu_semaphore.h
+++ b/third_party/nsync/mu_semaphore.h
@@ -12,13 +12,13 @@ typedef struct nsync_semaphore_s_ {
 void nsync_mu_semaphore_init(nsync_semaphore *s);
 
 /* Wait until the count of *s exceeds 0, and decrement it. */
-void nsync_mu_semaphore_p(nsync_semaphore *s);
+errno_t nsync_mu_semaphore_p(nsync_semaphore *s);
 
 /* Wait until one of: the count of *s is non-zero, in which case
    decrement *s and return 0; or abs_deadline expires, in which case
    return ETIMEDOUT. */
-int nsync_mu_semaphore_p_with_deadline(nsync_semaphore *s,
-                                       nsync_time abs_deadline);
+errno_t nsync_mu_semaphore_p_with_deadline(nsync_semaphore *s,
+                                           nsync_time abs_deadline);
 
 /* Ensure that the count of *s is at least 1. */
 void nsync_mu_semaphore_v(nsync_semaphore *s);
diff --git a/third_party/sqlite3/README.cosmo b/third_party/sqlite3/README.cosmo
index df74597f3..d61fcf0e9 100644
--- a/third_party/sqlite3/README.cosmo
+++ b/third_party/sqlite3/README.cosmo
@@ -17,4 +17,5 @@ LOCAL CHANGES
   - Added `--strace` system call tracing flag to SQLite shell
   - Added `--strace` function call logging flag to SQLite shell
   - Configured fsync() using runtime magnums rather than ifdefs
+  - Modify preprocessor macro for enabling pread() and pwrite()
   - Save and restore errno in some places to avoid log pollution
diff --git a/third_party/sqlite3/os_unix.c b/third_party/sqlite3/os_unix.c
index 5b0350517..00281e861 100644
--- a/third_party/sqlite3/os_unix.c
+++ b/third_party/sqlite3/os_unix.c
@@ -84,7 +84,7 @@
 #endif
 
 /* Use pread() and pwrite() if they are available */
-#if defined(__APPLE__) || defined(__COSMOPOLITAN__)
+#if defined(__APPLE__) || defined(__COSMOPOLITAN__) /* [jart] */
 # define HAVE_PREAD 1
 # define HAVE_PWRITE 1
 #endif
diff --git a/third_party/sqlite3/sqlite3.mk b/third_party/sqlite3/sqlite3.mk
index a1c984505..85acb556d 100644
--- a/third_party/sqlite3/sqlite3.mk
+++ b/third_party/sqlite3/sqlite3.mk
@@ -126,7 +126,7 @@ THIRD_PARTY_SQLITE3_FLAGS =						\
 	-DSQLITE_HAVE_C99_MATH_FUNCS					\
 	-DSQLITE_ENABLE_MATH_FUNCTIONS					\
 	-DSQLITE_ENABLE_JSON1						\
-	-DSQLITE_ENABLE_DESERIALIZE \
+	-DSQLITE_ENABLE_DESERIALIZE
 
 ifeq ($(MODE),dbg)
 THIRD_PARTY_SQLITE3_CPPFLAGS_DEBUG = -DSQLITE_DEBUG