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https://github.com/jart/cosmopolitan.git
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3c61a541bd
This is one of the few POSIX APIs that was missing. It lets you choose a monotonic clock for your condition variables. This might improve perf on some platforms. It might also grant more flexibility with NTP configs. I know Qt is one project that believes it needs this. To introduce this, I needed to change some the *NSYNC APIs, to support passing a clock param. There's also new benchmarks, demonstrating Cosmopolitan's supremacy over many libc implementations when it comes to mutex performance. Cygwin has an alarmingly bad pthread_mutex_t implementation. It is so bad that they would have been significantly better off if they'd used naive spinlocks.
77 lines
3.8 KiB
C
77 lines
3.8 KiB
C
/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
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│ vi: set noet ft=c ts=8 sw=8 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2016 Google Inc. │
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│ │
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│ Licensed under the Apache License, Version 2.0 (the "License"); │
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│ you may not use this file except in compliance with the License. │
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│ You may obtain a copy of the License at │
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│ │
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│ http://www.apache.org/licenses/LICENSE-2.0 │
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│ │
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│ Unless required by applicable law or agreed to in writing, software │
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│ distributed under the License is distributed on an "AS IS" BASIS, │
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│ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. │
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│ See the License for the specific language governing permissions and │
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│ limitations under the License. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/errno.h"
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#include "libc/intrin/dll.h"
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#include "libc/runtime/runtime.h"
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#include "third_party/nsync/atomic.h"
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#include "third_party/nsync/atomic.internal.h"
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#include "third_party/nsync/common.internal.h"
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#include "third_party/nsync/mu_semaphore.h"
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#include "third_party/nsync/wait_s.internal.h"
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__static_yoink("nsync_notice");
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/* Wait until one of:
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w->sem is non-zero----decrement it and return 0.
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abs_deadline expires---return ETIMEDOUT.
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cancel_note is non-NULL and *cancel_note becomes notified---return ECANCELED. */
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int nsync_sem_wait_with_cancel_ (waiter *w, int clock, nsync_time abs_deadline,
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nsync_note cancel_note) {
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int sem_outcome;
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if (cancel_note == NULL) {
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sem_outcome = nsync_mu_semaphore_p_with_deadline (&w->sem, clock, abs_deadline);
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} else {
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nsync_time cancel_time;
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cancel_time = nsync_note_notified_deadline_ (cancel_note);
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sem_outcome = ECANCELED;
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if (nsync_time_cmp (cancel_time, nsync_time_zero) > 0) {
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struct nsync_waiter_s nw;
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nw.tag = NSYNC_WAITER_TAG;
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nw.sem = &w->sem;
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dll_init (&nw.q);
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ATM_STORE (&nw.waiting, 1);
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nw.flags = 0;
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nsync_mu_lock (&cancel_note->note_mu);
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cancel_time = NOTIFIED_TIME (cancel_note);
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if (nsync_time_cmp (cancel_time, nsync_time_zero) > 0) {
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nsync_time local_abs_deadline;
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int deadline_is_nearer = 0;
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dll_make_last (&cancel_note->waiters, &nw.q);
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local_abs_deadline = cancel_time;
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if (nsync_time_cmp (abs_deadline, cancel_time) < 0) {
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local_abs_deadline = abs_deadline;
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deadline_is_nearer = 1;
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}
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nsync_mu_unlock (&cancel_note->note_mu);
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sem_outcome = nsync_mu_semaphore_p_with_deadline (&w->sem,
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clock, local_abs_deadline);
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if (sem_outcome == ETIMEDOUT && !deadline_is_nearer) {
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sem_outcome = ECANCELED;
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nsync_note_notify (cancel_note);
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}
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nsync_mu_lock (&cancel_note->note_mu);
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cancel_time = NOTIFIED_TIME (cancel_note);
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if (nsync_time_cmp (cancel_time,
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nsync_time_zero) > 0) {
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dll_remove (&cancel_note->waiters, &nw.q);
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}
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}
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nsync_mu_unlock (&cancel_note->note_mu);
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}
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}
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return (sem_outcome);
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}
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