Implement pthread_atfork()

If threads are being used, then fork() will now acquire and release and
runtime locks so that fork() may be safely used from threads. This also
makes vfork() thread safe, because pthread mutexes will do nothing when
the process is a child of vfork(). More torture tests have been written
to confirm this all works like a charm. Additionally:

- Invent hexpcpy() api
- Rename nsync_malloc_() to kmalloc()
- Complete posix named semaphore implementation
- Make pthread_create() asynchronous signal safe
- Add rm, rmdir, and touch to command interpreter builtins
- Invent sigisprecious() and modify sigset functions to use it
- Add unit tests for posix_spawn() attributes and fix its bugs

One unresolved problem is the reclaiming of *NSYNC waiter memory in the
forked child processes, within apps which have threads waiting on locks

third_party/nsync/README.cosmo

@@ -0,0 +1,19 @@
+DESCRIPTION
+
+  *NSYNC is a synchronization primitives library.
+
+LICENSE
+
+  Apache 2.0
+
+ORIGIN
+
+  git@github.com:google/nsync
+  commit ac5489682760393fe21bd2a8e038b528442412a7
+  Author: Mike Burrows <m3b@google.com>
+  Date:   Wed Jun 1 16:47:52 2022 -0700
+
+LOCAL CHANGES
+
+  - nsync_malloc_() is implemented as kmalloc()
+  - nsync_mu_semaphore uses Cosmopolitan Futexes

third_party/nsync/common.c

@@ -15,6 +15,7 @@
 │ See the License for the specific language governing permissions and          │
 │ limitations under the License.                                               │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/intrin/kmalloc.h"
 #include "libc/mem/mem.h"
 #include "libc/runtime/runtime.h"
 #include "libc/thread/thread.h"
@@ -23,7 +24,6 @@
 #include "third_party/nsync/atomic.internal.h"
 #include "third_party/nsync/common.internal.h"
 #include "third_party/nsync/dll.h"
-#include "third_party/nsync/malloc.internal.h"
 #include "third_party/nsync/mu_semaphore.h"
 #include "third_party/nsync/races.internal.h"
 #include "third_party/nsync/wait_s.internal.h"
@@ -188,7 +188,7 @@ waiter *nsync_waiter_new_ (void) {
 		}
 		ATM_STORE_REL (&free_waiters_mu, 0); /* release store */
 		if (w == NULL) { /* If free list was empty, allocate an item. */
-			w = (waiter *) nsync_malloc_ (sizeof (*w));
+			w = (waiter *) kmalloc (sizeof (*w));
 			w->tag = WAITER_TAG;
 			w->nw.tag = NSYNC_WAITER_TAG;
 			nsync_mu_semaphore_init (&w->sem);

third_party/nsync/common.internal.h

@@ -13,7 +13,9 @@
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 COSMOPOLITAN_C_START_
 
-#ifndef NSYNC_DEBUG
+#ifdef MODE_DBG
+#define NSYNC_DEBUG 1
+#else
 #define NSYNC_DEBUG 0
 #endif
 

third_party/nsync/futex.c

@@ -43,8 +43,6 @@
 #include "third_party/nsync/time.h"
 // clang-format off
 
-/* futex() polyfill w/ sched_yield() fallback */
-
 #define FUTEX_WAIT_BITS_ FUTEX_BITSET_MATCH_ANY
 
 int _futex (atomic_int *, int, int, const struct timespec *, int *, int);
@@ -161,6 +159,11 @@ int nsync_futex_wait_ (atomic_int *w, int expect, char pshare, struct timespec *
 		op |= FUTEX_PRIVATE_FLAG_;
 	}
 
+	LOCKTRACE ("futex(%t [%d], %s, %#x, %s) → ...",
+		   w, atomic_load_explicit (w, memory_order_relaxed),
+		   DescribeFutexOp (op), expect,
+		   DescribeTimespec (0, timeout));
+
 	if (FUTEX_IS_SUPPORTED) {
 		if (IsWindows ()) {
 			// Windows 8 futexes don't support multiple processes :(
@@ -199,7 +202,8 @@ int nsync_futex_wait_ (atomic_int *w, int expect, char pshare, struct timespec *
 	}
 
 	STRACE ("futex(%t [%d], %s, %#x, %s) → %s",
-		w, *w, DescribeFutexOp (op), expect,
+		w, atomic_load_explicit (w, memory_order_relaxed),
+		DescribeFutexOp (op), expect,
 		DescribeTimespec (0, timeout),
 		DescribeErrnoResult (rc));
 
@@ -208,7 +212,7 @@ 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 (void *, int, int) asm ("_futex");
+	int wake (atomic_int *, int, int) asm ("_futex");
 
 	ASSERT (count == 1 || count == INT_MAX);
 
@@ -245,8 +249,8 @@ int nsync_futex_wake_ (atomic_int *w, int count, char pshare) {
 	}
 
 	STRACE ("futex(%t [%d], %s, %d) → %s",
-		w, *w, DescribeFutexOp(op),
-		count, DescribeErrnoResult(rc));
+		w, atomic_load_explicit (w, memory_order_relaxed),
+		DescribeFutexOp(op), count, DescribeErrnoResult(rc));
 
 	return rc;
 }

third_party/nsync/malloc.c

@@ -1,52 +0,0 @@
-/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8   -*-│
-│vi: set et ft=c 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/atomic.h"
-#include "libc/intrin/atomic.h"
-#include "libc/intrin/extend.internal.h"
-#include "libc/macros.internal.h"
-#include "libc/runtime/memtrack.internal.h"
-#include "libc/sysv/consts/map.h"
-#include "third_party/nsync/common.internal.h"
-#include "third_party/nsync/malloc.internal.h"
-// clang-format off
-
-static char *nsync_malloc_endptr_;
-static size_t nsync_malloc_total_;
-static atomic_char nsync_malloc_lock_;
-
-/* nsync_malloc_() is a malloc-like routine used by mutex and condition
-   variable code to allocate waiter structs. This allows *NSYNC mutexes
-   to be used by malloc(), by providing another, simpler allocator here.
-   The intent is that the implicit NULL value here can be overridden by
-   a client declaration that uses an initializer. */
-void *nsync_malloc_ (size_t size) {
-	char *start;
-	size_t offset;
-	size = ROUNDUP (size, __BIGGEST_ALIGNMENT__);
-	while (atomic_exchange (&nsync_malloc_lock_, 1)) nsync_yield_ ();
-	offset = nsync_malloc_total_;
-	nsync_malloc_total_ += size;
-	start = (char *) kMemtrackNsyncStart;
-	if (!nsync_malloc_endptr_) nsync_malloc_endptr_ = start;
-	nsync_malloc_endptr_ =
-		_extend (start, nsync_malloc_total_, nsync_malloc_endptr_,
-			 MAP_PRIVATE, kMemtrackNsyncStart + kMemtrackNsyncSize);
-	atomic_store_explicit (&nsync_malloc_lock_, 0, memory_order_relaxed);
-	return start + offset;
-}

third_party/nsync/malloc.internal.h

@@ -1,10 +0,0 @@
-#ifndef NSYNC_MALLOC_INTERNAL_H_
-#define NSYNC_MALLOC_INTERNAL_H_
-#if !(__ASSEMBLER__ + __LINKER__ + 0)
-COSMOPOLITAN_C_START_
-
-void *nsync_malloc_(size_t);
-
-COSMOPOLITAN_C_END_
-#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
-#endif /* NSYNC_MALLOC_INTERNAL_H_ */