security_events: Fix error caused by DTD validation error
[asterisk/asterisk.git] / funcs / func_lock.c
index 53b05a3..2102d5c 100644 (file)
  * 
  */
 
+/*** MODULEINFO
+       <support_level>core</support_level>
+ ***/
+
 #include "asterisk.h"
 
 ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 
+#include <signal.h>
+
 #include "asterisk/lock.h"
 #include "asterisk/file.h"
 #include "asterisk/channel.h"
 #include "asterisk/pbx.h"
 #include "asterisk/module.h"
 #include "asterisk/linkedlists.h"
-
-AST_LIST_HEAD_STATIC(locklist, lock_frame);
+#include "asterisk/astobj2.h"
+#include "asterisk/utils.h"
+
+/*** DOCUMENTATION
+       <function name="LOCK" language="en_US">
+               <synopsis>
+                       Attempt to obtain a named mutex.
+               </synopsis>
+               <syntax>
+                       <parameter name="lockname" required="true" />
+               </syntax>
+               <description>
+                       <para>Attempts to grab a named lock exclusively, and prevents other channels from
+                       obtaining the same lock.  LOCK will wait for the lock to become available.
+                       Returns <literal>1</literal> if the lock was obtained or <literal>0</literal> on error.</para>
+                       <note><para>To avoid the possibility of a deadlock, LOCK will only attempt to
+                       obtain the lock for 3 seconds if the channel already has another lock.</para></note>
+                       <note>
+                               <para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
+                               is set to <literal>no</literal>, this function can only be executed from the
+                               dialplan, and not directly from external protocols.</para>
+                       </note>
+               </description>
+       </function>
+       <function name="TRYLOCK" language="en_US">
+               <synopsis>
+                       Attempt to obtain a named mutex.
+               </synopsis>
+               <syntax>
+                       <parameter name="lockname" required="true" />
+               </syntax>
+               <description>
+                       <para>Attempts to grab a named lock exclusively, and prevents other channels
+                       from obtaining the same lock.  Returns <literal>1</literal> if the lock was 
+                       available or <literal>0</literal> otherwise.</para>
+                       <note>
+                               <para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
+                               is set to <literal>no</literal>, this function can only be executed from the
+                               dialplan, and not directly from external protocols.</para>
+                       </note>
+               </description>
+       </function>
+       <function name="UNLOCK" language="en_US">
+               <synopsis>
+                       Unlocks a named mutex.
+               </synopsis>
+               <syntax>
+                       <parameter name="lockname" required="true" />
+               </syntax>
+               <description>
+                       <para>Unlocks a previously locked mutex. Returns <literal>1</literal> if the channel 
+                       had a lock or <literal>0</literal> otherwise.</para>
+                       <note><para>It is generally unnecessary to unlock in a hangup routine, as any locks 
+                       held are automatically freed when the channel is destroyed.</para></note>
+                       <note>
+                               <para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
+                               is set to <literal>no</literal>, this function can only be executed from the
+                               dialplan, and not directly from external protocols.</para>
+                       </note>
+               </description>
+       </function>
+ ***/
+
+
+
+static AST_LIST_HEAD_STATIC(locklist, lock_frame);
 
 static void lock_free(void *data);
+static void lock_fixup(void *data, struct ast_channel *oldchan, struct ast_channel *newchan);
 static int unloading = 0;
+static pthread_t broker_tid = AST_PTHREADT_NULL;
 
-static struct ast_datastore_info lock_info = {
+static const struct ast_datastore_info lock_info = {
        .type = "MUTEX",
        .destroy = lock_free,
+       .chan_fixup = lock_fixup,
 };
 
 struct lock_frame {
        AST_LIST_ENTRY(lock_frame) entries;
        ast_mutex_t mutex;
+       ast_cond_t cond;
        /*! count is needed so if a recursive mutex exits early, we know how many times to unlock it. */
        unsigned int count;
+       /*! Container of requesters for the named lock */
+       struct ao2_container *requesters;
        /*! who owns us */
-       struct ast_channel *channel;
+       struct ast_channel *owner;
        /*! name of the lock */
        char name[0];
 };
@@ -72,12 +148,9 @@ static void lock_free(void *data)
        AST_LIST_LOCK(oldlist);
        while ((clframe = AST_LIST_REMOVE_HEAD(oldlist, list))) {
                /* Only unlock if we own the lock */
-               if (clframe->channel == clframe->lock_frame->channel) {
-                       clframe->lock_frame->channel = NULL;
-                       while (clframe->lock_frame->count > 0) {
-                               clframe->lock_frame->count--;
-                               ast_mutex_unlock(&clframe->lock_frame->mutex);
-                       }
+               if (clframe->channel == clframe->lock_frame->owner) {
+                       clframe->lock_frame->count = 0;
+                       clframe->lock_frame->owner = NULL;
                }
                ast_free(clframe);
        }
@@ -86,17 +159,89 @@ static void lock_free(void *data)
        ast_free(oldlist);
 }
 
-static int get_lock(struct ast_channel *chan, char *lockname, int try)
+static void lock_fixup(void *data, struct ast_channel *oldchan, struct ast_channel *newchan)
+{
+       struct ast_datastore *lock_store = ast_channel_datastore_find(oldchan, &lock_info, NULL);
+       AST_LIST_HEAD(, channel_lock_frame) *list;
+       struct channel_lock_frame *clframe = NULL;
+
+       if (!lock_store) {
+               return;
+       }
+       list = lock_store->data;
+
+       AST_LIST_LOCK(list);
+       AST_LIST_TRAVERSE(list, clframe, list) {
+               if (clframe->lock_frame->owner == oldchan) {
+                       clframe->lock_frame->owner = newchan;
+               }
+               /* We don't move requesters, because the thread stack is different */
+               clframe->channel = newchan;
+       }
+       AST_LIST_UNLOCK(list);
+}
+
+static void *lock_broker(void *unused)
+{
+       struct lock_frame *frame;
+       struct timespec forever = { 1000000, 0 };
+       for (;;) {
+               int found_requester = 0;
+
+               /* Test for cancel outside of the lock */
+               pthread_testcancel();
+               AST_LIST_LOCK(&locklist);
+
+               AST_LIST_TRAVERSE(&locklist, frame, entries) {
+                       if (ao2_container_count(frame->requesters)) {
+                               found_requester++;
+                               ast_mutex_lock(&frame->mutex);
+                               if (!frame->owner) {
+                                       ast_cond_signal(&frame->cond);
+                               }
+                               ast_mutex_unlock(&frame->mutex);
+                       }
+               }
+
+               AST_LIST_UNLOCK(&locklist);
+               pthread_testcancel();
+
+               /* If there are no requesters, then wait for a signal */
+               if (!found_requester) {
+                       nanosleep(&forever, NULL);
+               } else {
+                       sched_yield();
+               }
+       }
+       /* Not reached */
+       return NULL;
+}
+
+static int ast_channel_hash_cb(const void *obj, const int flags)
+{
+       const struct ast_channel *chan = obj;
+       return ast_str_case_hash(ast_channel_name(chan));
+}
+
+static int ast_channel_cmp_cb(void *obj, void *arg, int flags)
+{
+       struct ast_channel *chan = obj, *cmp_args = arg;
+       return strcasecmp(ast_channel_name(chan), ast_channel_name(cmp_args)) ? 0 : CMP_MATCH;
+}
+
+static int get_lock(struct ast_channel *chan, char *lockname, int trylock)
 {
        struct ast_datastore *lock_store = ast_channel_datastore_find(chan, &lock_info, NULL);
        struct lock_frame *current;
-       struct channel_lock_frame *clframe = NULL, *save_clframe = NULL;
+       struct channel_lock_frame *clframe = NULL;
        AST_LIST_HEAD(, channel_lock_frame) *list;
-       int res, count_channel_locks = 0;
+       int res = 0;
+       struct timespec timeout = { 0, };
+       struct timeval now;
 
        if (!lock_store) {
-               ast_debug(1, "Channel %s has no lock datastore, so we're allocating one.\n", chan->name);
-               lock_store = ast_channel_datastore_alloc(&lock_info, NULL);
+               ast_debug(1, "Channel %s has no lock datastore, so we're allocating one.\n", ast_channel_name(chan));
+               lock_store = ast_datastore_alloc(&lock_info, NULL);
                if (!lock_store) {
                        ast_log(LOG_ERROR, "Unable to allocate new datastore.  No locks will be obtained.\n");
                        return -1;
@@ -104,8 +249,10 @@ static int get_lock(struct ast_channel *chan, char *lockname, int try)
 
                list = ast_calloc(1, sizeof(*list));
                if (!list) {
-                       ast_log(LOG_ERROR, "Unable to allocate datastore list head.  %sLOCK will fail.\n", try ? "TRY" : "");
-                       ast_channel_datastore_free(lock_store);
+                       ast_log(LOG_ERROR,
+                               "Unable to allocate datastore list head.  %sLOCK will fail.\n",
+                               trylock ? "TRY" : "");
+                       ast_datastore_free(lock_store);
                        return -1;
                }
 
@@ -137,8 +284,27 @@ static int get_lock(struct ast_channel *chan, char *lockname, int try)
                        return -1;
                }
 
-               strcpy((char *)current + sizeof(*current), lockname);
-               ast_mutex_init(&current->mutex);
+               strcpy(current->name, lockname); /* SAFE */
+               if ((res = ast_mutex_init(&current->mutex))) {
+                       ast_log(LOG_ERROR, "Unable to initialize mutex: %s\n", strerror(res));
+                       ast_free(current);
+                       AST_LIST_UNLOCK(&locklist);
+                       return -1;
+               }
+               if ((res = ast_cond_init(&current->cond, NULL))) {
+                       ast_log(LOG_ERROR, "Unable to initialize condition variable: %s\n", strerror(res));
+                       ast_mutex_destroy(&current->mutex);
+                       ast_free(current);
+                       AST_LIST_UNLOCK(&locklist);
+                       return -1;
+               }
+               if (!(current->requesters = ao2_container_alloc(1, ast_channel_hash_cb, ast_channel_cmp_cb))) {
+                       ast_mutex_destroy(&current->mutex);
+                       ast_cond_destroy(&current->cond);
+                       ast_free(current);
+                       AST_LIST_UNLOCK(&locklist);
+                       return -1;
+               }
                AST_LIST_INSERT_TAIL(&locklist, current, entries);
        }
        AST_LIST_UNLOCK(&locklist);
@@ -146,67 +312,91 @@ static int get_lock(struct ast_channel *chan, char *lockname, int try)
        /* Found lock or created one - now find or create the corresponding link in the channel */
        AST_LIST_LOCK(list);
        AST_LIST_TRAVERSE(list, clframe, list) {
-               if (clframe->lock_frame == current)
-                       save_clframe = clframe;
-
-               /* Only count mutexes that we currently hold */
-               if (clframe->lock_frame->channel == chan)
-                       count_channel_locks++;
+               if (clframe->lock_frame == current) {
+                       break;
+               }
        }
 
-       if (save_clframe) {
-               clframe = save_clframe;
-       } else {
+       if (!clframe) {
                if (unloading) {
                        /* Don't bother */
                        AST_LIST_UNLOCK(list);
                        return -1;
                }
 
-               clframe = ast_calloc(1, sizeof(*clframe));
-               if (!clframe) {
-                       ast_log(LOG_ERROR, "Unable to allocate channel lock frame.  %sLOCK will fail.\n", try ? "TRY" : "");
+               if (!(clframe = ast_calloc(1, sizeof(*clframe)))) {
+                       ast_log(LOG_ERROR,
+                               "Unable to allocate channel lock frame.  %sLOCK will fail.\n",
+                               trylock ? "TRY" : "");
                        AST_LIST_UNLOCK(list);
                        return -1;
                }
 
                clframe->lock_frame = current;
                clframe->channel = chan;
-               /* Count the lock just created */
-               count_channel_locks++;
                AST_LIST_INSERT_TAIL(list, clframe, list);
        }
        AST_LIST_UNLOCK(list);
 
-       /* Okay, we have both frames, so now we need to try to lock the mutex. */
-       if (count_channel_locks > 1) {
-               struct timeval start = ast_tvnow();
-               for (;;) {
-                       if ((res = ast_mutex_trylock(&current->mutex)) == 0)
-                               break;
-                       if (ast_tvdiff_ms(ast_tvnow(), start) > 3000)
-                               break; /* bail after 3 seconds of waiting */
-                       usleep(1);
-               }
-       } else {
-               /* If the channel doesn't have any locks so far, then there's no possible deadlock. */
-               res = try ? ast_mutex_trylock(&current->mutex) : ast_mutex_lock(&current->mutex);
+       /* If we already own the lock, then we're being called recursively.
+        * Keep track of how many times that is, because we need to unlock
+        * the same amount, before we'll release this one.
+        */
+       if (current->owner == chan) {
+               current->count++;
+               return 0;
        }
 
-       if (res == 0) {
+       /* Okay, we have both frames, so now we need to try to lock.
+        *
+        * Locking order: always lock locklist first.  We need the
+        * locklist lock because the broker thread counts whether
+        * there are requesters with the locklist lock held, and we
+        * need to hold it, so that when we send our signal, below,
+        * to wake up the broker thread, it definitely will see that
+        * a requester exists at that point in time.  Otherwise, we
+        * could add to the requesters after it has already seen that
+        * that lock is unoccupied and wait forever for another signal.
+        */
+       AST_LIST_LOCK(&locklist);
+       ast_mutex_lock(&current->mutex);
+       /* Add to requester list */
+       ao2_link(current->requesters, chan);
+       pthread_kill(broker_tid, SIGURG);
+       AST_LIST_UNLOCK(&locklist);
+
+       /* Wait up to three seconds from now for LOCK. */
+       now = ast_tvnow();
+       timeout.tv_sec = now.tv_sec + 3;
+       timeout.tv_nsec = now.tv_usec * 1000;
+
+       if (!current->owner
+               || (!trylock
+                       && !(res = ast_cond_timedwait(&current->cond, &current->mutex, &timeout)))) {
+               res = 0;
+               current->owner = chan;
                current->count++;
-               current->channel = chan;
+       } else {
+               res = -1;
        }
+       /* Remove from requester list */
+       ao2_unlink(current->requesters, chan);
+       ast_mutex_unlock(&current->mutex);
 
        return res;
 }
 
 static int unlock_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
 {
-       struct ast_datastore *lock_store = ast_channel_datastore_find(chan, &lock_info, NULL);
+       struct ast_datastore *lock_store;
        struct channel_lock_frame *clframe;
        AST_LIST_HEAD(, channel_lock_frame) *list;
 
+       if (!chan) {
+               return -1;
+       }
+
+       lock_store = ast_channel_datastore_find(chan, &lock_info, NULL);
        if (!lock_store) {
                ast_log(LOG_WARNING, "No datastore for dialplan locks.  Nothing was ever locked!\n");
                ast_copy_string(buf, "0", len);
@@ -222,7 +412,7 @@ static int unlock_read(struct ast_channel *chan, const char *cmd, char *data, ch
        /* Find item in the channel list */
        AST_LIST_LOCK(list);
        AST_LIST_TRAVERSE(list, clframe, list) {
-               if (clframe->lock_frame && clframe->lock_frame->channel == chan && strcmp(clframe->lock_frame->name, data) == 0) {
+               if (clframe->lock_frame && clframe->lock_frame->owner == chan && strcmp(clframe->lock_frame->name, data) == 0) {
                        break;
                }
        }
@@ -237,76 +427,54 @@ static int unlock_read(struct ast_channel *chan, const char *cmd, char *data, ch
                return 0;
        }
 
-       /* Decrement before we release, because if a channel is waiting on the
-        * mutex, there's otherwise a race to alter count. */
-       clframe->lock_frame->count--;
-       /* If we get another lock, this one shouldn't count against us for deadlock avoidance. */
-       clframe->lock_frame->channel = NULL;
-       ast_mutex_unlock(&clframe->lock_frame->mutex);
+       if (--clframe->lock_frame->count == 0) {
+               clframe->lock_frame->owner = NULL;
+       }
 
        ast_copy_string(buf, "1", len);
        return 0;
 }
 
 static int lock_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
-{      
-       if (chan)
-               ast_autoservice_start(chan);
-
+{
+       if (!chan) {
+               return -1;
+       }
+       ast_autoservice_start(chan);
        ast_copy_string(buf, get_lock(chan, data, 0) ? "0" : "1", len);
-
-       if (chan)
-               ast_autoservice_stop(chan);
+       ast_autoservice_stop(chan);
 
        return 0;
 }
 
 static int trylock_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
 {
-       if (chan)
-               ast_autoservice_start(chan);
-
+       if (!chan) {
+               return -1;
+       }
+       ast_autoservice_start(chan);
        ast_copy_string(buf, get_lock(chan, data, 1) ? "0" : "1", len);
-
-       if (chan)
-               ast_autoservice_stop(chan);
+       ast_autoservice_stop(chan);
 
        return 0;
 }
 
 static struct ast_custom_function lock_function = {
        .name = "LOCK",
-       .synopsis = "Attempt to obtain a named mutex",
-       .desc =
-"Attempts to grab a named lock exclusively, and prevents other channels from\n"
-"obtaining the same lock.  LOCK will wait for the lock to become available.\n"
-"Returns 1 if the lock was obtained or 0 on error.\n\n"
-"Note: to avoid the possibility of a deadlock, LOCK will only attempt to\n"
-"obtain the lock for 3 seconds if the channel already has another lock.\n",
-       .syntax = "LOCK(<lockname>)",
        .read = lock_read,
+       .read_max = 2,
 };
 
 static struct ast_custom_function trylock_function = {
        .name = "TRYLOCK",
-       .synopsis = "Attempt to obtain a named mutex",
-       .desc =
-"Attempts to grab a named lock exclusively, and prevents other channels\n"
-"from obtaining the same lock.  Returns 1 if the lock was available or 0\n"
-"otherwise.\n",
-       .syntax = "TRYLOCK(<lockname>)",
        .read = trylock_read,
+       .read_max = 2,
 };
 
 static struct ast_custom_function unlock_function = {
        .name = "UNLOCK",
-       .synopsis = "Unlocks a named mutex",
-       .desc =
-"Unlocks a previously locked mutex.  Note that it is generally unnecessary to\n"
-"unlock in a hangup routine, as any locks held are automatically freed when the\n"
-"channel is destroyed.  Returns 1 if the channel had a lock or 0 otherwise.\n",
-       .syntax = "UNLOCK(<lockname>)",
        .read = unlock_read,
+       .read_max = 2,
 };
 
 static int unload_module(void)
@@ -319,7 +487,7 @@ static int unload_module(void)
        AST_LIST_LOCK(&locklist);
        while ((current = AST_LIST_REMOVE_HEAD(&locklist, entries))) {
                /* If any locks are currently in use, then we cannot unload this module */
-               if (current->channel) {
+               if (current->owner || ao2_container_count(current->requesters)) {
                        /* Put it back */
                        AST_LIST_INSERT_HEAD(&locklist, current, entries);
                        AST_LIST_UNLOCK(&locklist);
@@ -327,6 +495,7 @@ static int unload_module(void)
                        return -1;
                }
                ast_mutex_destroy(&current->mutex);
+               ao2_ref(current->requesters, -1);
                ast_free(current);
        }
 
@@ -335,15 +504,30 @@ static int unload_module(void)
        ast_custom_function_unregister(&trylock_function);
        ast_custom_function_unregister(&unlock_function);
 
+       if (broker_tid != AST_PTHREADT_NULL) {
+               pthread_cancel(broker_tid);
+               pthread_kill(broker_tid, SIGURG);
+               pthread_join(broker_tid, NULL);
+       }
+
        AST_LIST_UNLOCK(&locklist);
+
        return 0;
 }
 
 static int load_module(void)
 {
-       int res = ast_custom_function_register(&lock_function);
-       res |= ast_custom_function_register(&trylock_function);
-       res |= ast_custom_function_register(&unlock_function);
+       int res = ast_custom_function_register_escalating(&lock_function, AST_CFE_READ);
+       res |= ast_custom_function_register_escalating(&trylock_function, AST_CFE_READ);
+       res |= ast_custom_function_register_escalating(&unlock_function, AST_CFE_READ);
+
+       if (ast_pthread_create_background(&broker_tid, NULL, lock_broker, NULL)) {
+               ast_log(LOG_ERROR, "Failed to start lock broker thread. Unloading func_lock module.\n");
+               broker_tid = AST_PTHREADT_NULL;
+               unload_module();
+               return AST_MODULE_LOAD_DECLINE;
+       }
+
        return res;
 }