Make locks more reliable

This change switches most of the core locks to be re-entrant, in order
to reduce the chance of deadlocking code that does, clever things with
asynchronous signal handlers. This change implements it it in pthreads
so we're one step closer to having a standardized threading primitives

libc/runtime/memtrack.internal.h

@@ -3,6 +3,7 @@
 #include "libc/assert.h"
 #include "libc/bits/midpoint.h"
 #include "libc/dce.h"
+#include "libc/intrin/pthread.h"
 #include "libc/macros.internal.h"
 #include "libc/nt/version.h"
 #include "libc/runtime/stack.h"
@@ -30,6 +31,9 @@ COSMOPOLITAN_C_START_
 #define _kMem(NORMAL, WIN7) \
   (!IsWindows() || IsAtLeastWindows10() ? NORMAL : WIN7)
 
+#define __mmi_lock()   pthread_mutex_lock(&_mmi.lock)
+#define __mmi_unlock() pthread_mutex_unlock(&_mmi.lock)
+
 struct MemoryInterval {
   int x;
   int y;
@@ -46,7 +50,7 @@ struct MemoryIntervals {
   size_t i, n;
   struct MemoryInterval *p;
   struct MemoryInterval s[OPEN_MAX];
-  _Alignas(64) int lock;
+  pthread_mutex_t lock;
 };
 
 extern hidden struct MemoryIntervals _mmi;

libc/runtime/mmap.c

@@ -31,6 +31,7 @@
 #include "libc/intrin/asancodes.h"
 #include "libc/intrin/describeflags.internal.h"
 #include "libc/intrin/kprintf.h"
+#include "libc/intrin/pthread.h"
 #include "libc/intrin/spinlock.h"
 #include "libc/limits.h"
 #include "libc/log/backtrace.internal.h"
@@ -404,13 +405,11 @@ static noasan inline void *Mmap(void *addr, size_t size, int prot, int flags,
 
   if (p != MAP_FAILED) {
     if (needguard) {
-      if (IsWindows()) _spunlock(&_mmi.lock);
       mprotect(p, PAGESIZE, PROT_NONE);
       if (IsAsan()) {
         __repstosb((void *)(((intptr_t)p >> 3) + 0x7fff8000),
                    kAsanStackOverflow, PAGESIZE / 8);
       }
-      if (IsWindows()) _spinlock(&_mmi.lock);
     }
   }
 
@@ -479,12 +478,12 @@ noasan void *mmap(void *addr, size_t size, int prot, int flags, int fd,
                   int64_t off) {
   void *res;
   size_t toto;
-  _spinlock(&_mmi.lock);
+  __mmi_lock();
   res = Mmap(addr, size, prot, flags, fd, off);
 #if SYSDEBUG
   toto = __strace > 0 ? GetMemtrackSize(&_mmi) : 0;
 #endif
-  _spunlock(&_mmi.lock);
+  __mmi_unlock();
   STRACE("mmap(%p, %'zu, %s, %s, %d, %'ld) → %p% m (%'zu bytes total)", addr,
          size, DescribeProtFlags(prot), DescribeMapFlags(flags), fd, off, res,
          toto);

libc/runtime/mprotect-nt.greg.c

@@ -29,7 +29,7 @@ textwindows int sys_mprotect_nt(void *addr, size_t size, int prot) {
   unsigned i;
   uint32_t op;
   char *a, *b, *x, *y, *p;
-  _spinlock(&_mmi.lock);
+  __mmi_lock();
   p = addr;
   i = FindMemoryInterval(&_mmi, (intptr_t)p >> 16);
   if (i == _mmi.i || (!i && p + size <= ADDR(_mmi.p[0].x))) {
@@ -58,6 +58,6 @@ textwindows int sys_mprotect_nt(void *addr, size_t size, int prot) {
       }
     }
   }
-  _spunlock(&_mmi.lock);
+  __mmi_unlock();
   return rc;
 }

libc/runtime/msync-nt.c

@@ -31,7 +31,7 @@
 noasan textwindows int sys_msync_nt(char *addr, size_t size, int flags) {
   int i, rc = 0;
   char *a, *b, *x, *y;
-  _spinlock(&_mmi.lock);
+  __mmi_lock();
   for (i = FindMemoryInterval(&_mmi, (intptr_t)addr >> 16); i < _mmi.i; ++i) {
     x = ADDR(_mmi.p[i].x);
     y = x + _mmi.p[i].size;
@@ -48,6 +48,6 @@ noasan textwindows int sys_msync_nt(char *addr, size_t size, int flags) {
       break;
     }
   }
-  _spunlock(&_mmi.lock);
+  __mmi_unlock();
   return rc;
 }

libc/runtime/munmap.c

@@ -164,12 +164,12 @@ static noasan int Munmap(char *p, size_t n) {
 noasan int munmap(void *p, size_t n) {
   int rc;
   size_t toto;
-  _spinlock(&_mmi.lock);
+  __mmi_lock();
   rc = Munmap(p, n);
 #if SYSDEBUG
   toto = __strace > 0 ? GetMemtrackSize(&_mmi) : 0;
 #endif
-  _spunlock(&_mmi.lock);
+  __mmi_unlock();
   STRACE("munmap(%.12p, %'zu) → %d% m (%'zu bytes total)", p, n, rc, toto);
   return rc;
 }

libc/runtime/printmaps.c

@@ -24,7 +24,7 @@
  * Prints memory mappings to stderr.
  */
 void __print_maps(void) {
-  _spinlock(&_mmi.lock);
+  __mmi_lock();
   PrintMemoryIntervals(2, &_mmi);
-  _spunlock(&_mmi.lock);
+  __mmi_unlock();
 }

libc/runtime/pthread.c

@@ -1,77 +0,0 @@
-/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
-│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
-╞══════════════════════════════════════════════════════════════════════════════╡
-│ Copyright 2021 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/bits/atomic.h"
-#include "libc/calls/calls.h"
-#include "libc/errno.h"
-#include "libc/intrin/lockcmpxchg.h"
-#include "libc/intrin/spinlock.h"
-#include "libc/runtime/runtime.h"
-
-typedef void *pthread_t;
-typedef int pthread_once_t;
-typedef int pthread_mutex_t;
-
-int pthread_once(pthread_once_t *once, void init(void)) {
-  int x;
-  unsigned tries;
-  switch ((x = atomic_load(once))) {
-    case 0:
-      if (atomic_compare_exchange_strong(once, &x, 1)) {
-        init();
-        atomic_store(once, 2);
-        break;
-      }
-      // fallthrough
-    case 1:
-      tries = 0;
-      do {
-        if (++tries & 7) {
-          __builtin_ia32_pause();
-        } else {
-          sched_yield();
-        }
-      } while (atomic_load(once) == 1);
-      break;
-    default:
-      break;
-  }
-  return 0;
-}
-
-int pthread_mutex_lock(pthread_mutex_t *mutex) {
-  _spinlock(mutex);
-  return 0;
-}
-
-int pthread_mutex_trylock(pthread_mutex_t *mutex) {
-  return _trylock(mutex);
-}
-
-int pthread_mutex_unlock(pthread_mutex_t *mutex) {
-  _spunlock(mutex);
-  return 0;
-}
-
-int pthread_cancel(pthread_t thread) {
-  return ESRCH;
-}
-
-void *__tls_get_addr(size_t v[2]) {
-  return NULL;
-}