mirror of
https://github.com/jart/cosmopolitan.git
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a359de7893
This changes *NSYNC to allocate waiters on the stack so our locks don't need to depend on dynamic memory. This make our runtiem simpler, and it also fixes bugs with thread cancellation support.
111 lines
4.3 KiB
C
111 lines
4.3 KiB
C
/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
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│vi: set et ft=c ts=8 tw=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/calls/blockcancel.internal.h"
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#include "libc/mem/mem.h"
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#include "libc/thread/thread.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/races.internal.h"
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#include "third_party/nsync/wait_s.internal.h"
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#include "third_party/nsync/waiter.h"
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asm(".ident\t\"\\n\\n\
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*NSYNC (Apache 2.0)\\n\
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Copyright 2016 Google, Inc.\\n\
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https://github.com/google/nsync\"");
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// clang-format off
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int nsync_wait_n (void *mu, void (*lock) (void *), void (*unlock) (void *),
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nsync_time abs_deadline,
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int count, struct nsync_waitable_s *waitable[]) {
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int ready;
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IGNORE_RACES_START ();
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BLOCK_CANCELLATIONS;
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for (ready = 0; ready != count &&
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nsync_time_cmp ((*waitable[ready]->funcs->ready_time) (
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waitable[ready]->v, NULL),
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nsync_time_zero) > 0;
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ready++) {
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}
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if (ready == count && nsync_time_cmp (abs_deadline, nsync_time_zero) > 0) {
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int i;
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int unlocked = 0;
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int j;
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int enqueued = 1;
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waiter w[1];
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nsync_waiter_init_ (w);
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struct nsync_waiter_s nw_set[4];
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struct nsync_waiter_s *nw = nw_set;
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if (count > (int) (sizeof (nw_set) / sizeof (nw_set[0]))) {
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nw = (struct nsync_waiter_s *) malloc (count * sizeof (nw[0]));
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}
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for (i = 0; i != count && enqueued; i++) {
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nw[i].tag = NSYNC_WAITER_TAG;
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nw[i].sem = &w->sem;
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dll_init (&nw[i].q);
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ATM_STORE (&nw[i].waiting, 0);
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nw[i].flags = 0;
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enqueued = (*waitable[i]->funcs->enqueue) (waitable[i]->v, &nw[i]);
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}
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if (i == count) {
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nsync_time min_ntime;
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if (mu != NULL) {
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(*unlock) (mu);
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unlocked = 1;
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}
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do {
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min_ntime = abs_deadline;
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for (j = 0; j != count; j++) {
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nsync_time ntime;
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ntime = (*waitable[j]->funcs->ready_time) (
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waitable[j]->v, &nw[j]);
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if (nsync_time_cmp (ntime, min_ntime) < 0) {
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min_ntime = ntime;
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}
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}
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} while (nsync_time_cmp (min_ntime, nsync_time_zero) > 0 &&
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nsync_mu_semaphore_p_with_deadline (&w->sem,
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min_ntime) == 0);
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}
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/* An attempt was made above to enqueue waitable[0..i-1].
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Dequeue any that are still enqueued, and remember the index
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of the first ready (i.e., not still enqueued) object, if any. */
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for (j = 0; j != i; j++) {
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int was_still_enqueued =
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(*waitable[j]->funcs->dequeue) (waitable[j]->v, &nw[j]);
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if (!was_still_enqueued && ready == count) {
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ready = j;
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}
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}
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nsync_waiter_destroy_ (w);
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if (nw != nw_set) {
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free (nw);
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}
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if (unlocked) {
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(*lock) (mu);
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}
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}
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ALLOW_CANCELLATIONS;
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IGNORE_RACES_END ();
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return (ready);
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}
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