While addressing a bug, I came across a instance of 'struct ast_datastore_info' that was not declared 'const'. Since the API already expects them to be 'const', this patch changes the declarations of all existing instances that were not already declared that way. ........ Merged revisions 370183 from http://svn.asterisk.org/svn/asterisk/branches/1.8 ........ Merged revisions 370184 from http://svn.asterisk.org/svn/asterisk/branches/10 git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@370187 65c4cc65-6c06-0410-ace0-fbb531ad65f3
520 lines
14 KiB
C
520 lines
14 KiB
C
/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 2007, Tilghman Lesher
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*
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* Tilghman Lesher <func_lock_2007@the-tilghman.com>
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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/*! \file
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*
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* \brief Dialplan mutexes
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*
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* \author Tilghman Lesher <func_lock_2007@the-tilghman.com>
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*
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* \ingroup functions
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*
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*/
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/*** MODULEINFO
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<support_level>core</support_level>
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***/
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#include "asterisk.h"
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ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
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#include <signal.h>
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#include "asterisk/lock.h"
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#include "asterisk/file.h"
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#include "asterisk/channel.h"
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#include "asterisk/pbx.h"
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#include "asterisk/module.h"
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#include "asterisk/linkedlists.h"
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#include "asterisk/astobj2.h"
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#include "asterisk/utils.h"
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/*** DOCUMENTATION
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<function name="LOCK" language="en_US">
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<synopsis>
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Attempt to obtain a named mutex.
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</synopsis>
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<syntax>
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<parameter name="lockname" required="true" />
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</syntax>
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<description>
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<para>Attempts to grab a named lock exclusively, and prevents other channels from
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obtaining the same lock. LOCK will wait for the lock to become available.
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Returns <literal>1</literal> if the lock was obtained or <literal>0</literal> on error.</para>
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<note><para>To avoid the possibility of a deadlock, LOCK will only attempt to
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obtain the lock for 3 seconds if the channel already has another lock.</para></note>
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</description>
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</function>
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<function name="TRYLOCK" language="en_US">
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<synopsis>
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Attempt to obtain a named mutex.
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</synopsis>
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<syntax>
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<parameter name="lockname" required="true" />
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</syntax>
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<description>
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<para>Attempts to grab a named lock exclusively, and prevents other channels
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from obtaining the same lock. Returns <literal>1</literal> if the lock was
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available or <literal>0</literal> otherwise.</para>
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</description>
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</function>
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<function name="UNLOCK" language="en_US">
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<synopsis>
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Unlocks a named mutex.
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</synopsis>
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<syntax>
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<parameter name="lockname" required="true" />
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</syntax>
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<description>
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<para>Unlocks a previously locked mutex. Returns <literal>1</literal> if the channel
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had a lock or <literal>0</literal> otherwise.</para>
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<note><para>It is generally unnecessary to unlock in a hangup routine, as any locks
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held are automatically freed when the channel is destroyed.</para></note>
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</description>
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</function>
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***/
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static AST_LIST_HEAD_STATIC(locklist, lock_frame);
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static void lock_free(void *data);
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static void lock_fixup(void *data, struct ast_channel *oldchan, struct ast_channel *newchan);
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static int unloading = 0;
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static pthread_t broker_tid = AST_PTHREADT_NULL;
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static const struct ast_datastore_info lock_info = {
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.type = "MUTEX",
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.destroy = lock_free,
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.chan_fixup = lock_fixup,
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};
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struct lock_frame {
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AST_LIST_ENTRY(lock_frame) entries;
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ast_mutex_t mutex;
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ast_cond_t cond;
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/*! count is needed so if a recursive mutex exits early, we know how many times to unlock it. */
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unsigned int count;
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/*! Container of requesters for the named lock */
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struct ao2_container *requesters;
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/*! who owns us */
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struct ast_channel *owner;
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/*! name of the lock */
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char name[0];
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};
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struct channel_lock_frame {
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AST_LIST_ENTRY(channel_lock_frame) list;
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/*! Need to save channel pointer here, because during destruction, we won't have it. */
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struct ast_channel *channel;
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struct lock_frame *lock_frame;
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};
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static void lock_free(void *data)
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{
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AST_LIST_HEAD(, channel_lock_frame) *oldlist = data;
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struct channel_lock_frame *clframe;
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AST_LIST_LOCK(oldlist);
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while ((clframe = AST_LIST_REMOVE_HEAD(oldlist, list))) {
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/* Only unlock if we own the lock */
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if (clframe->channel == clframe->lock_frame->owner) {
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clframe->lock_frame->count = 0;
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clframe->lock_frame->owner = NULL;
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}
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ast_free(clframe);
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}
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AST_LIST_UNLOCK(oldlist);
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AST_LIST_HEAD_DESTROY(oldlist);
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ast_free(oldlist);
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}
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static void lock_fixup(void *data, struct ast_channel *oldchan, struct ast_channel *newchan)
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{
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struct ast_datastore *lock_store = ast_channel_datastore_find(oldchan, &lock_info, NULL);
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AST_LIST_HEAD(, channel_lock_frame) *list;
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struct channel_lock_frame *clframe = NULL;
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if (!lock_store) {
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return;
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}
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list = lock_store->data;
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AST_LIST_LOCK(list);
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AST_LIST_TRAVERSE(list, clframe, list) {
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if (clframe->lock_frame->owner == oldchan) {
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clframe->lock_frame->owner = newchan;
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}
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/* We don't move requesters, because the thread stack is different */
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clframe->channel = newchan;
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}
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AST_LIST_UNLOCK(list);
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}
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static void *lock_broker(void *unused)
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{
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struct lock_frame *frame;
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struct timespec forever = { 1000000, 0 };
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for (;;) {
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int found_requester = 0;
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/* Test for cancel outside of the lock */
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pthread_testcancel();
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AST_LIST_LOCK(&locklist);
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AST_LIST_TRAVERSE(&locklist, frame, entries) {
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if (ao2_container_count(frame->requesters)) {
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found_requester++;
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ast_mutex_lock(&frame->mutex);
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if (!frame->owner) {
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ast_cond_signal(&frame->cond);
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}
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ast_mutex_unlock(&frame->mutex);
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}
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}
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AST_LIST_UNLOCK(&locklist);
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pthread_testcancel();
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/* If there are no requesters, then wait for a signal */
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if (!found_requester) {
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nanosleep(&forever, NULL);
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} else {
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sched_yield();
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}
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}
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/* Not reached */
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return NULL;
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}
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static int ast_channel_hash_cb(const void *obj, const int flags)
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{
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const struct ast_channel *chan = obj;
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return ast_str_case_hash(ast_channel_name(chan));
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}
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static int ast_channel_cmp_cb(void *obj, void *arg, int flags)
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{
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struct ast_channel *chan = obj, *cmp_args = arg;
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return strcasecmp(ast_channel_name(chan), ast_channel_name(cmp_args)) ? 0 : CMP_MATCH;
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}
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static int get_lock(struct ast_channel *chan, char *lockname, int trylock)
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{
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struct ast_datastore *lock_store = ast_channel_datastore_find(chan, &lock_info, NULL);
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struct lock_frame *current;
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struct channel_lock_frame *clframe = NULL;
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AST_LIST_HEAD(, channel_lock_frame) *list;
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int res = 0;
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struct timespec timeout = { 0, };
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struct timeval now;
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if (!lock_store) {
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ast_debug(1, "Channel %s has no lock datastore, so we're allocating one.\n", ast_channel_name(chan));
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lock_store = ast_datastore_alloc(&lock_info, NULL);
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if (!lock_store) {
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ast_log(LOG_ERROR, "Unable to allocate new datastore. No locks will be obtained.\n");
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return -1;
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}
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list = ast_calloc(1, sizeof(*list));
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if (!list) {
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ast_log(LOG_ERROR,
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"Unable to allocate datastore list head. %sLOCK will fail.\n",
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trylock ? "TRY" : "");
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ast_datastore_free(lock_store);
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return -1;
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}
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lock_store->data = list;
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AST_LIST_HEAD_INIT(list);
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ast_channel_datastore_add(chan, lock_store);
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} else
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list = lock_store->data;
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/* Lock already exists? */
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AST_LIST_LOCK(&locklist);
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AST_LIST_TRAVERSE(&locklist, current, entries) {
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if (strcmp(current->name, lockname) == 0) {
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break;
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}
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}
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if (!current) {
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if (unloading) {
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/* Don't bother */
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AST_LIST_UNLOCK(&locklist);
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return -1;
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}
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/* Create new lock entry */
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current = ast_calloc(1, sizeof(*current) + strlen(lockname) + 1);
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if (!current) {
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AST_LIST_UNLOCK(&locklist);
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return -1;
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}
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strcpy(current->name, lockname); /* SAFE */
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if ((res = ast_mutex_init(¤t->mutex))) {
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ast_log(LOG_ERROR, "Unable to initialize mutex: %s\n", strerror(res));
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ast_free(current);
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AST_LIST_UNLOCK(&locklist);
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return -1;
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}
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if ((res = ast_cond_init(¤t->cond, NULL))) {
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ast_log(LOG_ERROR, "Unable to initialize condition variable: %s\n", strerror(res));
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ast_mutex_destroy(¤t->mutex);
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ast_free(current);
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AST_LIST_UNLOCK(&locklist);
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return -1;
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}
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if (!(current->requesters = ao2_container_alloc(1, ast_channel_hash_cb, ast_channel_cmp_cb))) {
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ast_mutex_destroy(¤t->mutex);
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ast_cond_destroy(¤t->cond);
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ast_free(current);
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AST_LIST_UNLOCK(&locklist);
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return -1;
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}
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AST_LIST_INSERT_TAIL(&locklist, current, entries);
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}
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AST_LIST_UNLOCK(&locklist);
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/* Found lock or created one - now find or create the corresponding link in the channel */
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AST_LIST_LOCK(list);
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AST_LIST_TRAVERSE(list, clframe, list) {
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if (clframe->lock_frame == current) {
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break;
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}
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}
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if (!clframe) {
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if (unloading) {
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/* Don't bother */
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AST_LIST_UNLOCK(list);
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return -1;
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}
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if (!(clframe = ast_calloc(1, sizeof(*clframe)))) {
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ast_log(LOG_ERROR,
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"Unable to allocate channel lock frame. %sLOCK will fail.\n",
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trylock ? "TRY" : "");
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AST_LIST_UNLOCK(list);
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return -1;
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}
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clframe->lock_frame = current;
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clframe->channel = chan;
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AST_LIST_INSERT_TAIL(list, clframe, list);
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}
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AST_LIST_UNLOCK(list);
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/* If we already own the lock, then we're being called recursively.
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* Keep track of how many times that is, because we need to unlock
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* the same amount, before we'll release this one.
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*/
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if (current->owner == chan) {
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current->count++;
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return 0;
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}
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/* Okay, we have both frames, so now we need to try to lock.
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*
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* Locking order: always lock locklist first. We need the
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* locklist lock because the broker thread counts whether
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* there are requesters with the locklist lock held, and we
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* need to hold it, so that when we send our signal, below,
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* to wake up the broker thread, it definitely will see that
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* a requester exists at that point in time. Otherwise, we
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* could add to the requesters after it has already seen that
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* that lock is unoccupied and wait forever for another signal.
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*/
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AST_LIST_LOCK(&locklist);
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ast_mutex_lock(¤t->mutex);
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/* Add to requester list */
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ao2_link(current->requesters, chan);
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pthread_kill(broker_tid, SIGURG);
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AST_LIST_UNLOCK(&locklist);
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/* Wait up to three seconds from now for LOCK. */
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now = ast_tvnow();
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timeout.tv_sec = now.tv_sec + 3;
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timeout.tv_nsec = now.tv_usec * 1000;
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if (!current->owner
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|| (!trylock
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&& !(res = ast_cond_timedwait(¤t->cond, ¤t->mutex, &timeout)))) {
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res = 0;
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current->owner = chan;
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current->count++;
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} else {
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res = -1;
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}
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/* Remove from requester list */
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ao2_unlink(current->requesters, chan);
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ast_mutex_unlock(¤t->mutex);
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return res;
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}
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static int unlock_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
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{
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struct ast_datastore *lock_store;
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struct channel_lock_frame *clframe;
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AST_LIST_HEAD(, channel_lock_frame) *list;
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if (!chan) {
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return -1;
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}
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lock_store = ast_channel_datastore_find(chan, &lock_info, NULL);
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if (!lock_store) {
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ast_log(LOG_WARNING, "No datastore for dialplan locks. Nothing was ever locked!\n");
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ast_copy_string(buf, "0", len);
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return 0;
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}
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if (!(list = lock_store->data)) {
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ast_debug(1, "This should NEVER happen\n");
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ast_copy_string(buf, "0", len);
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return 0;
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}
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/* Find item in the channel list */
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AST_LIST_LOCK(list);
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AST_LIST_TRAVERSE(list, clframe, list) {
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if (clframe->lock_frame && clframe->lock_frame->owner == chan && strcmp(clframe->lock_frame->name, data) == 0) {
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break;
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}
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}
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/* We never destroy anything until channel destruction, which will never
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* happen while this routine is executing, so we don't need to hold the
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* lock beyond this point. */
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AST_LIST_UNLOCK(list);
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if (!clframe) {
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/* We didn't have this lock in the first place */
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ast_copy_string(buf, "0", len);
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return 0;
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}
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if (--clframe->lock_frame->count == 0) {
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clframe->lock_frame->owner = NULL;
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}
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ast_copy_string(buf, "1", len);
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return 0;
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}
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static int lock_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
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{
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if (!chan) {
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return -1;
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}
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ast_autoservice_start(chan);
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ast_copy_string(buf, get_lock(chan, data, 0) ? "0" : "1", len);
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ast_autoservice_stop(chan);
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return 0;
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}
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static int trylock_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
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{
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if (!chan) {
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return -1;
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}
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ast_autoservice_start(chan);
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ast_copy_string(buf, get_lock(chan, data, 1) ? "0" : "1", len);
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ast_autoservice_stop(chan);
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return 0;
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}
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static struct ast_custom_function lock_function = {
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.name = "LOCK",
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.read = lock_read,
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.read_max = 2,
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};
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static struct ast_custom_function trylock_function = {
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.name = "TRYLOCK",
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.read = trylock_read,
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.read_max = 2,
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};
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static struct ast_custom_function unlock_function = {
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.name = "UNLOCK",
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.read = unlock_read,
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.read_max = 2,
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};
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static int unload_module(void)
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{
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struct lock_frame *current;
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/* Module flag */
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unloading = 1;
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AST_LIST_LOCK(&locklist);
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while ((current = AST_LIST_REMOVE_HEAD(&locklist, entries))) {
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/* If any locks are currently in use, then we cannot unload this module */
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if (current->owner || ao2_container_count(current->requesters)) {
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/* Put it back */
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AST_LIST_INSERT_HEAD(&locklist, current, entries);
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AST_LIST_UNLOCK(&locklist);
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unloading = 0;
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return -1;
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}
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ast_mutex_destroy(¤t->mutex);
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ao2_ref(current->requesters, -1);
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ast_free(current);
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}
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/* No locks left, unregister functions */
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ast_custom_function_unregister(&lock_function);
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ast_custom_function_unregister(&trylock_function);
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ast_custom_function_unregister(&unlock_function);
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if (broker_tid != AST_PTHREADT_NULL) {
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pthread_cancel(broker_tid);
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pthread_kill(broker_tid, SIGURG);
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pthread_join(broker_tid, NULL);
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}
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AST_LIST_UNLOCK(&locklist);
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return 0;
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}
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static int load_module(void)
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{
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int res = ast_custom_function_register(&lock_function);
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res |= ast_custom_function_register(&trylock_function);
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res |= ast_custom_function_register(&unlock_function);
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if (ast_pthread_create_background(&broker_tid, NULL, lock_broker, NULL)) {
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ast_log(LOG_ERROR, "Failed to start lock broker thread. Unloading func_lock module.\n");
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broker_tid = AST_PTHREADT_NULL;
|
|
unload_module();
|
|
return AST_MODULE_LOAD_DECLINE;
|
|
}
|
|
|
|
return res;
|
|
}
|
|
|
|
AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Dialplan mutexes");
|