cosmopolitan/libc/thread/pthread_exit.c
Justine Tunney 4a6fd3d910
Make more improvements to threading support
- fix rare thread exit race condition on openbsd
- pthread_getattr_np() now supplies detached status
- child threads may now pthread_join() the main thread
- introduce sigandset(), sigorset(), and sigisemptyset()
- introduce pthread_cleanup_push() and pthread_cleanup_pop()
2022-10-09 00:08:47 -07:00

93 lines
4.5 KiB
C

/*-*- 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/dce.h"
#include "libc/limits.h"
#include "libc/mem/gc.h"
#include "libc/runtime/runtime.h"
#include "libc/thread/posixthread.internal.h"
#include "libc/thread/thread.h"
#include "libc/thread/tls.h"
#include "third_party/nsync/futex.internal.h"
STATIC_YOINK("_pthread_main");
/**
* Terminates current POSIX thread.
*
* For example, a thread could terminate early as follows:
*
* pthread_exit((void *)123);
*
* The result value could then be obtained when joining the thread:
*
* void *rc;
* pthread_join(id, &rc);
* assert((intptr_t)rc == 123);
*
* Under normal circumstances a thread can exit by simply returning from
* the callback function that was supplied to pthread_create(). This may
* be used if the thread wishes to exit at any other point in the thread
* lifecycle, in which case this function is responsible for ensuring we
* invoke _gc(), _defer(), and pthread_cleanup_push() callbacks, as well
* as pthread_key_create() destructors.
*
* If the current thread is an orphaned thread, or is the main thread
* when no other threads were created, then this will terminated your
* process with an exit code of zero. It's not possible to supply a
* non-zero exit status to wait4() via this function.
*
* Once a thread has exited, access to its stack memory is undefined.
* The behavior of calling pthread_exit() from cleanup handlers and key
* destructors is also undefined.
*
* @param rc is reported later to pthread_join()
* @threadsafe
* @noreturn
*/
wontreturn void pthread_exit(void *rc) {
struct PosixThread *pt;
struct _pthread_cleanup_buffer *cb;
pt = (struct PosixThread *)__get_tls()->tib_pthread;
pt->rc = rc;
// the memory of pthread cleanup objects lives on the stack
// so we need to harvest them before calling longjmp()
while ((cb = pt->cleanup)) {
pt->cleanup = cb->__prev;
cb->__routine(cb->__arg);
}
if (~pt->flags & PT_MAINTHREAD) {
// this thread was created by pthread_create()
// garbage collector memory exists on a shadow stack. we don't need
// to use _gclongjmp() since _pthread_ungarbage() will collect them
// at the setjmp() site.
longjmp(pt->exiter, 1);
} else {
// this is the main thread
// release as much resources and possible and mark it terminated
_pthread_cleanup(pt);
// it's kind of irregular for a child thread to join the main thread
// so we don't bother freeing the main thread's stack since it makes
// this implementation so much simpler for example we want't to call
// set_tid_address() upon every program startup which isn't possible
// on non-linux platforms anyway.
__get_tls()->tib_tid = 0;
nsync_futex_wake_((int *)&__get_tls()->tib_tid, INT_MAX, !IsWindows());
_Exit1(0);
}
}