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Recorded merge of revisions 221044 via svnmerge from

Browse Source 
https://origsvn.digium.com/svn/asterisk/trunk

........
  r221044 | tilghman | 2009-09-29 23:32:36 -0500 (Tue, 29 Sep 2009) | 8 lines
  
  Allow locks to be inherited through a masquerade without causing starvation.
  (closes issue #14859)
   Reported by: atis
   Patches: 
         20090821__issue14859.diff.txt uploaded by tilghman (license 14)
         20090925__issue14859__1.6.1.diff.txt uploaded by tilghman (license 14)
   Tested by: atis, tilghman
........


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.2@221047 65c4cc65-6c06-0410-ace0-fbb531ad65f3
1.6.2
Tilghman Lesher 16 years ago
parent 4ddccae801
commit a1a3188102
1 changed files with 165 additions and 48 deletions
Show Stats Download Patch File Download Diff File

213
funcs/func_lock.c
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@ -30,12 +30,16 @@
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"
#include "asterisk/astobj2.h"
#include "asterisk/utils.h"
/*** DOCUMENTATION
<function name="LOCK" language="en_US">
@ -87,20 +91,26 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
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 = -1;
static 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];
};
@ -119,12 +129,9 @@ 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);
}
@ -133,13 +140,82 @@ static void lock_free(void *data)
ast_free(oldlist);
}
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 null_hash_cb(const void *obj, const int flags)
{
return (int)(long) obj;
}
static int null_cmp_cb(void *obj, void *arg, int flags)
{
return obj == arg ? CMP_MATCH : 0;
}
static int get_lock(struct ast_channel *chan, char *lockname, int try)
{
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, *link;
struct timespec three_seconds = { .tv_sec = 3 };
if (!lock_store) {
ast_debug(1, "Channel %s has no lock datastore, so we're allocating one.\n", chan->name);
@ -184,8 +260,27 @@ 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(7, null_hash_cb, null_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);
@ -193,25 +288,19 @@ 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) {
if (!(clframe = ast_calloc(1, sizeof(*clframe)))) {
ast_log(LOG_ERROR, "Unable to allocate channel lock frame. %sLOCK will fail.\n", try ? "TRY" : "");
AST_LIST_UNLOCK(list);
return -1;
@ -219,31 +308,55 @@ static int get_lock(struct ast_channel *chan, char *lockname, int try)
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) {
/* Link is just an empty flag, used to check whether more than one channel
* is contending for the lock. */
if (!(link = ao2_alloc(sizeof(*link), NULL))) {
return -1;
}
/* 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, link);
pthread_kill(broker_tid, SIGURG);
AST_LIST_UNLOCK(&locklist);
if ((!current->owner) ||
(!try && !(res = ast_cond_timedwait(&current->cond, &current->mutex, &three_seconds)))) {
res = 0;
current->owner = chan;
current->count++;
current->channel = chan;
} else {
res = -1;
}
/* Remove from requester list */
ao2_unlink(current->requesters, link);
ao2_ref(link, -1);
ast_mutex_unlock(&current->mutex);
return res;
}
@ -269,7 +382,7 @@ 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;
}
}
@ -284,19 +397,16 @@ 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);
@ -346,7 +456,7 @@ 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);
@ -354,6 +464,7 @@ static int unload_module(void)
return -1;
}
ast_mutex_destroy(&current->mutex);
ao2_ref(current->requesters, -1);
ast_free(current);
}
@ -362,7 +473,12 @@ static int unload_module(void)
ast_custom_function_unregister(&trylock_function);
ast_custom_function_unregister(&unlock_function);
pthread_cancel(broker_tid);
pthread_kill(broker_tid, SIGURG);
pthread_join(broker_tid, NULL);
AST_LIST_UNLOCK(&locklist);
return 0;
}
@ -371,6 +487,7 @@ 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);
ast_pthread_create_background(&broker_tid, NULL, lock_broker, NULL);
return res;
}

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