cosmopolitan/libc/thread/pthread_decimate_np.c
Justine Tunney 98c5847727
Fix fork waiter leak in nsync
This change fixes a bug where nsync waiter objects would leak. It'd mean
that long-running programs like runitd would run out of file descriptors
on NetBSD where waiter objects have ksem file descriptors. On other OSes
this bug is mostly harmless since the worst that can happen with a futex
is to leak a little bit of ram. The bug was caused because tib_nsync was
sneaking back in after the finalization code had cleared it. This change
refactors the thread exiting code to handle nsync teardown appropriately
and in making this change I found another issue, which is that user code
which is buggy, and tries to exit without joining joinable threads which
haven't been detached, would result in a deadlock. That doesn't sound so
bad, except the main thread is a joinable thread. So this deadlock would
be triggered in ways that put libc at fault. So we now auto-join threads
and libc will log a warning to --strace when that happens for any thread
2024-12-31 01:30:13 -08:00

47 lines
2.8 KiB
C

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2024 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/cosmo.h"
#include "libc/intrin/stack.h"
#include "libc/thread/posixthread.internal.h"
#include "libc/thread/thread.h"
/**
* Garbage collects POSIX threads runtime.
*
* This function frees unreferenced zombie threads and empties cache
* memory associated with the Cosmopolitan POSIX threads runtime.
*
* Here's an example use case for this function. Let's say you want to
* create a malloc() memory leak detector. If your program was running
* threads earlier, then there might still be allocations lingering
* around, that'll give you false positives. To fix this, what you would
* do is call the following, right before running your leak detector:
*
* while (!pthread_orphan_np())
* pthread_decimate_np();
*
* Which will wait until all threads have exited and their memory freed.
*
* @return 0 on success, or errno on error
*/
int pthread_decimate_np(void) {
_pthread_decimate(kPosixThreadZombie);
cosmo_stack_clear();
return 0;
}