Improve threading and i/o routines

- On Windows connect() can now be interrupted by a signal; connect() w/
  O_NONBLOCK will now raise EINPROGRESS; and connect() with SO_SNDTIMEO
  will raise ETIMEDOUT after the interval has elapsed.

- We now get the AcceptEx(), ConnectEx(), and TransmitFile() functions
  from the WIN32 API the officially blessed way, using WSAIoctl().

- Do nothing on Windows when fsync() is called on a directory handle.
  This was raising EACCES earlier becaues GENERIC_WRITE is required on
  the handle. It's possible to FlushFileBuffers() a directory handle if
  it's opened with write access but MSDN doesn't document what it does.
  If you have any idea, please let us know!

- Prefer manual reset event objects for read() and write() on Windows.

- Do some code cleanup on our dlmalloc customizations.

- Fix errno type error in Windows blocking routines.

- Make the futex polyfill simpler and faster.

third_party/nsync/futex.c

@@ -38,6 +38,7 @@
 #include "libc/nexgen32e/vendor.internal.h"
 #include "libc/nt/runtime.h"
 #include "libc/nt/synchronization.h"
+#include "libc/runtime/clktck.h"
 #include "libc/sysv/consts/clock.h"
 #include "libc/sysv/consts/timer.h"
 #include "libc/sysv/errfuns.h"
@@ -129,46 +130,19 @@ static void nsync_futex_init_ (void) {
 }
 
 static int nsync_futex_polyfill_ (atomic_int *w, int expect, struct timespec *abstime) {
-	int rc;
-	int64_t nanos, maxnanos;
-	struct timespec now, wait, remain, deadline;
-
-	if (!abstime) {
-		deadline = timespec_max;
-	} else {
-		deadline = *abstime;
-	}
-
-	nanos = 100;
-	maxnanos = __SIG_LOCK_INTERVAL_MS * 1000L * 1000;
 	for (;;) {
 		if (atomic_load_explicit (w, memory_order_acquire) != expect) {
 			return 0;
 		}
-		now = timespec_real ();
-		if (atomic_load_explicit (w, memory_order_acquire) != expect) {
-			return 0;
+		if (_weaken (pthread_testcancel_np) &&
+		    _weaken (pthread_testcancel_np) ()) {
+			return -ETIMEDOUT;
 		}
-		if (timespec_cmp (now, deadline) >= 0) {
-			break;
-		}
-		wait = timespec_fromnanos (nanos);
-		remain = timespec_sub (deadline, now);
-		if (timespec_cmp(wait, remain) > 0) {
-			wait = remain;
-		}
-		if ((rc = clock_nanosleep (CLOCK_REALTIME, 0, &wait, 0))) {
-			return -rc;
-		}
-		if (nanos < maxnanos) {
-			nanos <<= 1;
-			if (nanos > maxnanos) {
-				nanos = maxnanos;
-			}
+		if (abstime && timespec_cmp (timespec_real (), *abstime) >= 0) {
+			return -ETIMEDOUT;
 		}
+		pthread_yield ();
 	}
-
-	return -ETIMEDOUT;
 }
 
 static int nsync_futex_wait_win32_ (atomic_int *w, int expect, char pshare,
@@ -189,7 +163,7 @@ static int nsync_futex_wait_win32_ (atomic_int *w, int expect, char pshare,
 			return etimedout();
 		}
 		remain = timespec_sub (deadline, now);
-		interval = timespec_frommillis (__SIG_LOCK_INTERVAL_MS);
+		interval = timespec_frommillis (5000);
 		wait = timespec_cmp (remain, interval) > 0 ? interval : remain;
 		if (atomic_load_explicit (w, memory_order_acquire) != expect) {
 			return 0;
@@ -274,7 +248,7 @@ int nsync_futex_wait_ (atomic_int *w, int expect, char pshare, const struct time
 				us = -1u;
 			}
 			rc = ulock_wait (op, w, expect, us);
-			if (rc > 0) rc = 0; // TODO(jart): What does it mean?
+			if (rc > 0) rc = 0; // don't care about #waiters
 		} else if (IsFreebsd ()) {
 			rc = sys_umtx_timedwait_uint (w, expect, pshare, timeout);
 		} else {
@@ -356,6 +330,7 @@ int nsync_futex_wake_ (atomic_int *w, int count, char pshare) {
 				op |= ULF_WAKE_ALL;
 			}
 			rc = ulock_wake (op, w, 0);
+			ASSERT (!rc || rc == -ENOENT);
 			if (!rc) {
 				rc = 1;
 			} else if (rc == -ENOENT) {

third_party/nsync/mu_semaphore.c

@@ -23,7 +23,7 @@
 /* Apple's ulock (part by Cosmo futexes) is an internal API, but:
    1. Unlike GCD it's cancellable, i.e. can be EINTR'd by signals
    2. We currently always use ulock anyway for joining threads */
-#define PREFER_GCD_OVER_ULOCK 0
+#define PREFER_GCD_OVER_ULOCK 1
 
 asm(".ident\t\"\\n\\n\
 *NSYNC (Apache 2.0)\\n\

third_party/nsync/mu_semaphore_gcd.c

@@ -20,6 +20,7 @@
 #include "libc/errno.h"
 #include "libc/intrin/strace.internal.h"
 #include "libc/intrin/weaken.h"
+#include "libc/runtime/clktck.h"
 #include "libc/runtime/syslib.internal.h"
 #include "libc/str/str.h"
 #include "libc/thread/posixthread.internal.h"
@@ -116,8 +117,7 @@ errno_t nsync_mu_semaphore_p_with_deadline_gcd (nsync_semaphore *s,
 	    (pt->pt_flags & PT_NOCANCEL)) {
 		result = nsync_dispatch_semaphore_wait (s, abs_deadline);
 	} else {
-		struct timespec now, until, slice;
-		slice = timespec_frommillis (__SIG_LOCK_INTERVAL_MS);
+		struct timespec now, until, slice = {0, 1000000000 / CLK_TCK};
 		for (;;) {
 			if (_weaken (pthread_testcancel_np) () == ECANCELED) {
 				result = ECANCELED;

third_party/nsync/panic.c

@@ -17,12 +17,17 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
-#include "libc/str/str.h"
+#include "libc/errno.h"
+#include "libc/intrin/describebacktrace.internal.h"
+#include "libc/runtime/runtime.h"
 #include "third_party/nsync/common.internal.h"
 // clang-format off
 
 /* Aborts after printing the nul-terminated string s[]. */
 void nsync_panic_ (const char *s) {
-	tinyprint (2, "nsync panic: ", s, NULL);
-	notpossible;
+	tinyprint(2, "error: nsync panic: ", s, "\n",
+		"cosmoaddr2line ", program_invocation_name, " ",
+		DescribeBacktrace (__builtin_frame_address (0)), "\n",
+		NULL);
+	_Exit (44);
 }