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Improve multithreading

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Justine Tunney 2024-07-21 06:41:30 -07:00
parent d3167126aa
commit 30afd6ddbb
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38 changed files with 752 additions and 174 deletions
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libc/thread/pthread_attr_setsigaltstacksize_np.c Normal file
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/*-*- 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 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/errno.h"
#include "libc/limits.h"
#include "libc/runtime/runtime.h"
#include "libc/thread/thread.h"
/**
* Defines size of cosmo-owned signal stack for thread.
*
* The sigaltstack() function is useful for writing robust programs that
* can recover from the occasional thread having a stack overflow rather
* than having the entire process crash. To use it normally, sigaltstack
* needs to be called at the start of each thread with a unique piece of
* memory. However this is challenging to do *correctly* without support
* from the POSIX threads runtime, since canceled or crashed threads may
* need to execute on the signal stack during pthread_exit() which would
* prevent a thread-local storage key destructor from free()'ing it.
*
* By default pthread_create() will not install a sigaltstack() on newly
* created threads. If this function is called, on the attributes object
* that gets passed to pthread_create(), then it'll use malloc() to make
* a stack for the thread using the size you specify here. The threading
* runtime will also free that memory safely after complete termination.
*
* pthread_t id;
* pthread_attr_t attr;
* pthread_attr_init(&attr);
* pthread_attr_setguardsize(&attr, getpagesize());
* pthread_attr_setsigaltstacksize_np(&attr, stacksize);
* pthread_create(&id, &attr, func, 0);
* pthread_attr_destroy(&attr);
* pthread_join(id, 0);
*
* Try using a size of `sysconf(_SC_SIGSTKSZ)`. If you want the smallest
* size possible, then `sysconf(_SC_MINSIGSTKSZ) + 2048` is probably the
* smallest value that can reasonably expected to work with pthread_exit
*
* struct sigaction sa;
* sigemptyset(&sa.sa_mask);
* sa.sa_flags = SA_SIGINFO | SA_ONSTACK;
* sa.sa_sigaction = on_crash_signal;
* sigaction(SIGSEGV, &sa, 0);
*
* Please note that in order for this to work, your handlers for signals
* such as SIGSEGV and SIGBUS need to use SA_ONSTACK in your sa_flags.
*
* @param stacksize contains stack size in bytes, or 0 to disable
* @return 0 on success, or errno on error
* @raise EINVAL if `stacksize` is less than `sysconf(_SC_MINSIGSTKSZ)`
*/
errno_t pthread_attr_setsigaltstacksize_np(pthread_attr_t *a,
size_t stacksize) {
if (stacksize) {
if (stacksize > INT_MAX)
return EINVAL;
if (stacksize < __get_minsigstksz())
return EINVAL;
}
a->__sigaltstacksize = stacksize;
return 0;
}