Make garbage collection thread safe

- You can now use _gc(malloc()) in multithreaded programs
- This change fixes a bug where fork() on NT disabled TLS
- Fixed TLS code morphing on XNU/NT, for R8-R15 registers

libc/thread/pthread_create.c

@@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/assert.h"
 #include "libc/calls/calls.h"
 #include "libc/errno.h"
 #include "libc/intrin/asan.internal.h"
@@ -24,7 +25,9 @@
 #include "libc/intrin/wait0.internal.h"
 #include "libc/intrin/weaken.h"
 #include "libc/mem/mem.h"
+#include "libc/nexgen32e/gc.internal.h"
 #include "libc/nexgen32e/gettls.h"
+#include "libc/nexgen32e/threaded.h"
 #include "libc/runtime/runtime.h"
 #include "libc/sysv/consts/clone.h"
 #include "libc/sysv/consts/map.h"
@@ -56,6 +59,7 @@ static int PosixThread(void *arg, int tid) {
   if (weaken(_pthread_key_destruct)) {
     weaken(_pthread_key_destruct)(0);
   }
+  cthread_ungarbage();
   if (atomic_load_explicit(&pt->status, memory_order_acquire) ==
       kPosixThreadDetached) {
     atomic_store_explicit(&pt->status, kPosixThreadZombie,
@@ -108,6 +112,7 @@ int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
   int rc, e = errno;
   struct PosixThread *pt;
   pthread_attr_t default_attr;
+  TlsIsRequired();
   _pthread_zombies_decimate();
 
   // default attributes

libc/thread/pthread_exit.c

@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/intrin/pthread.h"
 #include "libc/nexgen32e/gettls.h"
+#include "libc/runtime/gc.h"
 #include "libc/thread/posixthread.internal.h"
 #include "libc/thread/spawn.h"
 #include "libc/thread/thread.h"
@@ -38,7 +39,7 @@ wontreturn void pthread_exit(void *rc) {
   struct PosixThread *pt;
   if ((pt = ((cthread_t)__get_tls())->pthread)) {
     pt->rc = rc;
-    longjmp(pt->exiter, 1);
+    _gclongjmp(pt->exiter, 1);
   } else {
     _Exit1((int)(intptr_t)rc);
   }

libc/thread/spawn.c

@@ -30,6 +30,7 @@
 #include "libc/sysv/consts/clone.h"
 #include "libc/sysv/consts/map.h"
 #include "libc/sysv/consts/prot.h"
+#include "libc/sysv/errfuns.h"
 #include "libc/thread/spawn.h"
 #include "libc/thread/thread.h"
 
@@ -54,6 +55,20 @@
 #define _TIBZ sizeof(struct cthread_descriptor_t)
 #define _MEMZ ROUNDUP(_TLSZ + _TIBZ, alignof(struct cthread_descriptor_t))
 
+struct spawner {
+  int (*fun)(void *, int);
+  void *arg;
+};
+
+static int Spawner(void *arg, int tid) {
+  int rc;
+  struct spawner *spawner = arg;
+  rc = spawner->fun(spawner->arg, tid);
+  cthread_ungarbage();
+  free(spawner);
+  return 0;
+}
+
 /**
  * Spawns thread, e.g.
  *
@@ -78,6 +93,9 @@
  */
 int _spawn(int fun(void *, int), void *arg, struct spawn *opt_out_thread) {
   struct spawn *th, ths;
+  struct spawner *spawner;
+  TlsIsRequired();
+  if (!fun) return einval();
 
   // we need to to clobber the output memory before calling clone, since
   // there's no guarantee clone() won't suspend the parent, and focus on
@@ -102,11 +120,14 @@ int _spawn(int fun(void *, int), void *arg, struct spawn *opt_out_thread) {
     return -1;
   }
 
-  if (clone(fun, th->stk, GetStackSize() - 16 /* openbsd:stackbound */,
+  spawner = malloc(sizeof(struct spawner));
+  spawner->fun = fun;
+  spawner->arg = arg;
+  if (clone(Spawner, th->stk, GetStackSize() - 16 /* openbsd:stackbound */,
             CLONE_VM | CLONE_THREAD | CLONE_FS | CLONE_FILES | CLONE_SIGHAND |
                 CLONE_SETTLS | CLONE_PARENT_SETTID | CLONE_CHILD_SETTID |
                 CLONE_CHILD_CLEARTID,
-            arg, &th->ptid, th->tib, th->ctid) == -1) {
+            spawner, &th->ptid, th->tib, th->ctid) == -1) {
     _freestack(th->stk);
     free(th->tls);
     return -1;

libc/thread/thread.h

@@ -28,7 +28,7 @@ struct FtraceTls {  /* 16 */
 struct cthread_descriptor_t {
   struct cthread_descriptor_t *self;  /* 0x00 */
   struct FtraceTls ftrace;            /* 0x08 */
-  void *garbages;                     /* 0x10 */
+  void *garbages;                     /* 0x18 */
   locale_t locale;                    /* 0x20 */
   pthread_t pthread;                  /* 0x28 */
   struct cthread_descriptor_t *self2; /* 0x30 */
@@ -64,6 +64,7 @@ int cthread_sem_wait(cthread_sem_t *, int, const struct timespec *);
 int cthread_sem_signal(cthread_sem_t *);
 int cthread_memory_wait32(int *, int, const struct timespec *);
 int cthread_memory_wake32(int *, int);
+void cthread_ungarbage(void);
 
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */

libc/thread/ungarbage.c

@@ -0,0 +1,34 @@
+/*-*- 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 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/assert.h"
+#include "libc/mem/mem.h"
+#include "libc/nexgen32e/gc.internal.h"
+#include "libc/nexgen32e/gettls.h"
+#include "libc/thread/thread.h"
+
+void cthread_ungarbage(void) {
+  struct Garbages *g;
+  if ((g = ((cthread_t)__get_tls())->garbages)) {
+    // _pthread_exit() uses _gclongjmp() so if this assertion fails,
+    // then the likely cause is the thread used gc() with longjmp().
+    assert(!g->i);
+    free(g->p);
+    free(g);
+  }
+}