mirrors/cosmopolitan
1
0
Fork 0
mirror of https://github.com/jart/cosmopolitan.git synced 2025-06-27 23:08:31 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

Make locks more reliable

Browse source 
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
This commit is contained in:
Justine Tunney 2022-06-11 01:59:26 -07:00
parent 5ea618f0af
commit c260345e06
35 changed files with 369 additions and 258 deletions
Download patch file Download diff file Expand all files Collapse all files

48
libc/intrin/pthread_once.c Normal file
View file

@ -0,0 +1,48 @@
/*-*- 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/bits/atomic.h"
#include "libc/calls/calls.h"
#include "libc/intrin/pthread.h"
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;
}