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simplify locking (use a single lock, no deadlock possible)

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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@6070 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Kevin P. Fleming
2005-07-10 13:06:54 +00:00
parent 3c8dfe099d
commit 87231c34a1
1 changed files with 13 additions and 18 deletions
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31
devicestate.c
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@@ -44,7 +44,6 @@ struct state_change {
static AST_LIST_HEAD_STATIC(state_changes, state_change); static AST_LIST_HEAD_STATIC(state_changes, state_change);
static pthread_t change_thread = AST_PTHREADT_NULL; static pthread_t change_thread = AST_PTHREADT_NULL;
AST_MUTEX_DEFINE_STATIC(change_pending_lock);
static pthread_cond_t change_pending; static pthread_cond_t change_pending;
int ast_parse_device_state(const char *device) int ast_parse_device_state(const char *device)
@@ -138,6 +137,7 @@ void ast_devstate_del(ast_devstate_cb_type callback, void *data)
AST_LIST_UNLOCK(&devstate_cbs); AST_LIST_UNLOCK(&devstate_cbs);
} }
/*--- do_state_change: Notify callback watchers of change, and notify PBX core for hint updates */
static void do_state_change(const char *device) static void do_state_change(const char *device)
{ {
int state; int state;
@@ -155,7 +155,6 @@ static void do_state_change(const char *device)
ast_hint_state_changed(device); ast_hint_state_changed(device);
} }
/*--- ast_device_state_changed: Notify callback watchers of change, and notify PBX core for hint updates */
int ast_device_state_changed(const char *fmt, ...) int ast_device_state_changed(const char *fmt, ...)
{ {
char buf[AST_MAX_EXTENSION]; char buf[AST_MAX_EXTENSION];
@@ -183,15 +182,10 @@ int ast_device_state_changed(const char *fmt, ...)
strcpy(change->device, device); strcpy(change->device, device);
AST_LIST_LOCK(&state_changes); AST_LIST_LOCK(&state_changes);
AST_LIST_INSERT_TAIL(&state_changes, change, list); AST_LIST_INSERT_TAIL(&state_changes, change, list);
if (AST_LIST_FIRST(&state_changes) == change) { if (AST_LIST_FIRST(&state_changes) == change)
AST_LIST_UNLOCK(&state_changes);
/* the list was empty, signal the thread */ /* the list was empty, signal the thread */
ast_mutex_lock(&change_pending_lock);
pthread_cond_signal(&change_pending); pthread_cond_signal(&change_pending);
ast_mutex_unlock(&change_pending_lock); AST_LIST_UNLOCK(&state_changes);
} else {
AST_LIST_UNLOCK(&state_changes);
}
} }
return 1; return 1;
@@ -201,20 +195,21 @@ static void *do_changes(void *data)
{ {
struct state_change *cur; struct state_change *cur;
AST_LIST_LOCK(&state_changes);
for(;;) { for(;;) {
ast_mutex_lock(&change_pending_lock); /* the list lock will _always_ be held at this point in the loop */
pthread_cond_wait(&change_pending, &change_pending_lock); cur = AST_LIST_REMOVE_HEAD(&state_changes, list);
for (;;) { if (cur) {
AST_LIST_LOCK(&state_changes); /* we got an entry, so unlock the list while we process it */
cur = AST_LIST_REMOVE_HEAD(&state_changes, list);
AST_LIST_UNLOCK(&state_changes); AST_LIST_UNLOCK(&state_changes);
if (!cur)
break;
do_state_change(cur->device); do_state_change(cur->device);
free(cur); free(cur);
AST_LIST_LOCK(&state_changes);
} else {
/* there was no entry, so atomically unlock the list and wait for
the condition to be signalled (returns with the lock held) */
pthread_cond_wait(&change_pending, &state_changes.lock);
} }
ast_mutex_unlock(&change_pending_lock);
} }
return NULL; return NULL;