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203 lines
6.5 KiB
203 lines
6.5 KiB
5 months ago
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/* Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License, version 2.0,
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as published by the Free Software Foundation.
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This program is also distributed with certain software (including
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but not limited to OpenSSL) that is licensed under separate terms,
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as designated in a particular file or component or in included license
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documentation. The authors of MySQL hereby grant you an additional
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permission to link the program and your derivative works with the
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separately licensed software that they have included with MySQL.
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Without limiting anything contained in the foregoing, this file,
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which is part of C Driver for MySQL (Connector/C), is also subject to the
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Universal FOSS Exception, version 1.0, a copy of which can be found at
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http://oss.oracle.com/licenses/universal-foss-exception.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License, version 2.0, for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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/**
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@file mysys/thr_mutex.cc
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*/
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#include "thr_mutex.h"
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#include <errno.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "my_dbug.h"
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#include "my_thread_local.h"
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#if defined(SAFE_MUTEX)
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/* This makes a wrapper for mutex handling to make it easier to debug mutex */
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static bool safe_mutex_inited = false;
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/**
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While it looks like this function is pointless, it makes it possible to
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catch usage of global static mutexes. Since the order of construction of
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global objects in different compilation units is undefined, this is
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quite useful.
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*/
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void safe_mutex_global_init(void) { safe_mutex_inited = true; }
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int safe_mutex_init(safe_mutex_t *mp, const native_mutexattr_t *attr,
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const char *file, uint line) {
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DBUG_ASSERT(safe_mutex_inited);
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memset(mp, 0, sizeof(*mp));
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native_mutex_init(&mp->global, MY_MUTEX_INIT_ERRCHK);
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native_mutex_init(&mp->mutex, attr);
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/* Mark that mutex is initialized */
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mp->file = file;
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mp->line = line;
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return 0;
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}
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int safe_mutex_lock(safe_mutex_t *mp, bool try_lock, const char *file,
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uint line) {
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int error;
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native_mutex_lock(&mp->global);
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if (!mp->file) {
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native_mutex_unlock(&mp->global);
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fprintf(stderr,
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"safe_mutex: Trying to lock uninitialized mutex at %s, line %d\n",
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file, line);
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fflush(stderr);
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abort();
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}
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if (mp->count > 0) {
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if (try_lock) {
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native_mutex_unlock(&mp->global);
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return EBUSY;
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} else if (my_thread_equal(my_thread_self(), mp->thread)) {
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#ifndef DBUG_OFF
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fprintf(stderr,
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"safe_mutex: Trying to lock mutex at %s, line %d, when the"
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" mutex was already locked at %s, line %d in thread T@%u\n",
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file, line, mp->file, mp->line, my_thread_var_id());
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fflush(stderr);
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#endif
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abort();
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}
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}
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native_mutex_unlock(&mp->global);
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/*
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If we are imitating trylock(), we need to take special
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precautions.
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- We cannot use pthread_mutex_lock() only since another thread can
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overtake this thread and take the lock before this thread
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causing pthread_mutex_trylock() to hang. In this case, we should
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just return EBUSY. Hence, we use pthread_mutex_trylock() to be
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able to return immediately.
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- We cannot just use trylock() and continue execution below, since
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this would generate an error and abort execution if the thread
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was overtaken and trylock() returned EBUSY . In this case, we
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instead just return EBUSY, since this is the expected behaviour
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of trylock().
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*/
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if (try_lock) {
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error = native_mutex_trylock(&mp->mutex);
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if (error == EBUSY) return error;
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} else
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error = native_mutex_lock(&mp->mutex);
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if (error || (error = native_mutex_lock(&mp->global))) {
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fprintf(stderr, "Got error %d when trying to lock mutex at %s, line %d\n",
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error, file, line);
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fflush(stderr);
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abort();
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}
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mp->thread = my_thread_self();
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if (mp->count++) {
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fprintf(stderr,
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"safe_mutex: Error in thread libray: Got mutex at %s, \
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line %d more than 1 time\n",
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file, line);
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fflush(stderr);
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abort();
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}
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mp->file = file;
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mp->line = line;
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native_mutex_unlock(&mp->global);
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return error;
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}
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int safe_mutex_unlock(safe_mutex_t *mp, const char *file, uint line) {
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int error;
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native_mutex_lock(&mp->global);
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if (mp->count == 0) {
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fprintf(stderr,
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"safe_mutex: Trying to unlock mutex that wasn't locked at %s, line "
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"%d\n Last used at %s, line: %d\n",
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file, line, mp->file ? mp->file : "", mp->line);
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fflush(stderr);
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abort();
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}
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if (!my_thread_equal(my_thread_self(), mp->thread)) {
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fprintf(stderr,
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"safe_mutex: Trying to unlock mutex at %s, line %d that was "
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"locked by another thread at: %s, line: %d\n",
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file, line, mp->file, mp->line);
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fflush(stderr);
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abort();
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}
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mp->thread = 0;
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mp->count--;
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error = native_mutex_unlock(&mp->mutex);
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if (error) {
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fprintf(stderr,
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"safe_mutex: Got error: %d (%d) when trying to unlock mutex at %s, "
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"line %d\n",
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error, errno, file, line);
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fflush(stderr);
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abort();
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}
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native_mutex_unlock(&mp->global);
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return error;
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}
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int safe_mutex_destroy(safe_mutex_t *mp, const char *file, uint line) {
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int error = 0;
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native_mutex_lock(&mp->global);
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if (!mp->file) {
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native_mutex_unlock(&mp->global);
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fprintf(
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stderr,
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"safe_mutex: Trying to destroy uninitialized mutex at %s, line %d\n",
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file, line);
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fflush(stderr);
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abort();
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}
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if (mp->count != 0) {
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native_mutex_unlock(&mp->global);
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fprintf(stderr,
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"safe_mutex: Trying to destroy a mutex that was locked at %s, line "
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"%d at %s, line %d\n",
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mp->file, mp->line, file, line);
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fflush(stderr);
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abort();
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}
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native_mutex_unlock(&mp->global);
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if (native_mutex_destroy(&mp->global)) error = 1;
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if (native_mutex_destroy(&mp->mutex)) error = 1;
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mp->file = 0; /* Mark destroyed */
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return error;
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}
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#endif /* SAFE_MUTEX */
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