/*-*- 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/asmflag.h" #include "libc/bits/atomic.h" #include "libc/calls/calls.h" #include "libc/dce.h" #include "libc/errno.h" #include "libc/intrin/pthread.h" #include "libc/intrin/spinlock.h" #include "libc/linux/futex.h" #include "libc/nexgen32e/threaded.h" #include "libc/sysv/consts/futex.h" #include "libc/sysv/consts/nr.h" static inline int FutexWait(void *addr, int expect, struct timespec *timeout) { int ax; bool cf; asm volatile(CFLAG_ASM("mov\t%6,%%r10\n\t" "clc\n\t" "syscall") : CFLAG_CONSTRAINT(cf), "=a"(ax) : "1"(__NR_futex), "D"(addr), "S"(FUTEX_WAIT), "d"(expect), "g"(timeout) : "rcx", "r10", "r11", "memory"); if (cf) ax = -ax; return ax; } static int pthread_mutex_lock_spin(pthread_mutex_t *mutex, int tries) { volatile int i; struct timespec ts; if (tries < 7) { for (i = 0; i != 1 << tries; i++) { } tries++; } else if (IsLinux() || IsOpenbsd()) { atomic_fetch_add(&mutex->waits, 1); if (tries < 28) { ts.tv_sec = 0; ts.tv_nsec = 4 << tries; tries++; } else { ts.tv_sec = 1; ts.tv_nsec = 0; } FutexWait(&mutex->lock, 1, &ts); atomic_fetch_sub(&mutex->waits, 1); } else { sched_yield(); } return tries; } /** * Locks mutex. * * _spinlock() l: 181,570c 58,646ns * mutex normal l: 297,965c 96,241ns * mutex recursive l: 1,112,166c 359,223ns * mutex errorcheck l: 1,449,723c 468,252ns * * @return 0 on success, or error number on failure */ int(pthread_mutex_lock)(pthread_mutex_t *mutex) { int me, owner, tries; switch (mutex->attr) { case PTHREAD_MUTEX_NORMAL: for (tries = 0;;) { if (!atomic_load_explicit(&mutex->lock, memory_order_relaxed) && !atomic_exchange_explicit(&mutex->lock, 1, memory_order_acquire)) { break; } tries = pthread_mutex_lock_spin(mutex, tries); } return 0; case PTHREAD_MUTEX_RECURSIVE: case PTHREAD_MUTEX_ERRORCHECK: for (tries = 0, me = gettid();;) { owner = atomic_load_explicit(&mutex->lock, memory_order_relaxed); if (!owner && atomic_compare_exchange_weak_explicit( &mutex->lock, &owner, me, memory_order_acquire, memory_order_relaxed)) { break; } else if (owner == me) { if (mutex->attr != PTHREAD_MUTEX_ERRORCHECK) { break; } else { return EDEADLK; } } tries = pthread_mutex_lock_spin(mutex, tries); } ++mutex->reent; return 0; default: return EINVAL; } }