3) In addition to merging the changes below, change trunk back to a regular

   LIST instead of an RWLIST.  The way this list works makes it such that
   a RWLIST provides no additional benefit.  Also, a mutex is needed for
   use with the thread condition.


Merged revisions 105563 via svnmerge from 
https://origsvn.digium.com/svn/asterisk/branches/1.4

........
r105563 | russell | 2008-03-03 09:50:43 -0600 (Mon, 03 Mar 2008) | 24 lines

Merge in some changes from team/russell/autoservice-nochans-1.4

These changes fix up some dubious code that I came across while auditing what
happens in the autoservice thread when there are no channels currently in
autoservice.

1) Change it so that autoservice thread doesn't keep looping around calling
   ast_waitfor_n() on 0 channels twice a second.  Instead, use a thread condition
   so that the thread properly goes to sleep and does not wake up until a
   channel is put into autoservice.

   This actually fixes an interesting bug, as well.  If the autoservice thread
   is already running (almost always is the case), then when the thread goes
   from having 0 channels to have 1 channel to autoservice, that channel would
   have to wait for up to 1/2 of a second to have the first frame read from it.

2) Fix up the code in ast_waitfor_nandfds() for when it gets called with no
   channels and no fds to poll() on, such as was the case with the previous code
   for the autoservice thread.  In this case, the code would call alloca(0), and
   pass the result as the first argument to poll().  In this case, the 2nd
   argument to poll() specified that there were no fds, so this invalid pointer
   shouldn't actually get dereferenced, but, this code makes it explicit and
   ensures the pointers are NULL unless we have valid data to put there.

(related to issue #12116)

........


git-svn-id: http://svn.digium.com/svn/asterisk/trunk@105564 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 35 insertions, 21 deletions

diff --git a/main/autoservice.c b/main/autoservice.c
index 7fb86dad7..74b1015ef 100644
--- a/main/autoservice.c
+++ b/main/autoservice.c
@@ -30,6 +30,8 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 #include <sys/time.h>
 #include <signal.h>
 
+#include "asterisk/_private.h" /* prototype for ast_autoservice_init() */
+
 #include "asterisk/pbx.h"
 #include "asterisk/frame.h"
 #include "asterisk/sched.h"
@@ -56,7 +58,8 @@ struct asent {
 	AST_LIST_ENTRY(asent) list;
 };
 
-static AST_RWLIST_HEAD_STATIC(aslist, asent);
+static AST_LIST_HEAD_STATIC(aslist, asent);
+static ast_cond_t as_cond;
 
 static pthread_t asthread = AST_PTHREADT_NULL;
 
@@ -67,14 +70,14 @@ static void defer_frame(struct ast_channel *chan, struct ast_frame *f)
 	struct ast_frame *dup_f;
 	struct asent *as;
 
-	AST_RWLIST_WRLOCK(&aslist);
-	AST_RWLIST_TRAVERSE(&aslist, as, list) {
+	AST_LIST_LOCK(&aslist);
+	AST_LIST_TRAVERSE(&aslist, as, list) {
 		if (as->chan != chan)
 			continue;
 		if ((dup_f = ast_frdup(f)))
 			AST_LIST_INSERT_TAIL(&as->dtmf_frames, dup_f, frame_list);
 	}
-	AST_RWLIST_UNLOCK(&aslist);
+	AST_LIST_UNLOCK(&aslist);
 }
 
 static void *autoservice_run(void *ign)
@@ -84,13 +87,16 @@ static void *autoservice_run(void *ign)
 		struct asent *as;
 		int x = 0, ms = 500;
 
-		AST_RWLIST_RDLOCK(&aslist);
+		AST_LIST_LOCK(&aslist);
 
 		/* At this point, we know that no channels that have been removed are going
 		 * to get used again. */
 		as_chan_list_state++;
 
-		AST_RWLIST_TRAVERSE(&aslist, as, list) {
+		if (AST_LIST_EMPTY(&aslist))
+			ast_cond_wait(&as_cond, &aslist.lock);
+
+		AST_LIST_TRAVERSE(&aslist, as, list) {
 			if (!ast_check_hangup(as->chan)) {
 				if (x < MAX_AUTOMONS)
 					mons[x++] = as->chan;
@@ -98,7 +104,8 @@ static void *autoservice_run(void *ign)
 					ast_log(LOG_WARNING, "Exceeded maximum number of automatic monitoring events.  Fix autoservice.c\n");
 			}
 		}
-		AST_RWLIST_UNLOCK(&aslist);
+
+		AST_LIST_UNLOCK(&aslist);
 
 		if ((chan = ast_waitfor_n(mons, x, &ms))) {
 			struct ast_frame *f = ast_read(chan);
@@ -158,14 +165,14 @@ int ast_autoservice_start(struct ast_channel *chan)
 	int res = 0;
 	struct asent *as;
 
-	AST_RWLIST_WRLOCK(&aslist);
-	AST_RWLIST_TRAVERSE(&aslist, as, list) {
+	AST_LIST_LOCK(&aslist);
+	AST_LIST_TRAVERSE(&aslist, as, list) {
 		if (as->chan == chan) {
 			as->use_count++;
 			break;
 		}
 	}
-	AST_RWLIST_UNLOCK(&aslist);
+	AST_LIST_UNLOCK(&aslist);
 
 	if (as) {
 		/* Entry exists, autoservice is already handling this channel */
@@ -185,18 +192,20 @@ int ast_autoservice_start(struct ast_channel *chan)
 		ast_set_flag(chan, AST_FLAG_END_DTMF_ONLY);
 	ast_channel_unlock(chan);
 
-	AST_RWLIST_WRLOCK(&aslist);
-	AST_RWLIST_INSERT_HEAD(&aslist, as, list);
-	AST_RWLIST_UNLOCK(&aslist);
+	AST_LIST_LOCK(&aslist);
+	if (AST_LIST_EMPTY(&aslist))
+		ast_cond_signal(&as_cond);
+	AST_LIST_INSERT_HEAD(&aslist, as, list);
+	AST_LIST_UNLOCK(&aslist);
 
 	if (asthread == AST_PTHREADT_NULL) { /* need start the thread */
 		if (ast_pthread_create_background(&asthread, NULL, autoservice_run, NULL)) {
 			ast_log(LOG_WARNING, "Unable to create autoservice thread :(\n");
 			/* There will only be a single member in the list at this point,
 			   the one we just added. */
-			AST_RWLIST_WRLOCK(&aslist);
-			AST_RWLIST_REMOVE(&aslist, as, list);
-			AST_RWLIST_UNLOCK(&aslist);
+			AST_LIST_LOCK(&aslist);
+			AST_LIST_REMOVE(&aslist, as, list);
+			AST_LIST_UNLOCK(&aslist);
 			free(as);
 			res = -1;
 		} else
@@ -218,7 +227,7 @@ int ast_autoservice_stop(struct ast_channel *chan)
 
 	AST_LIST_HEAD_INIT_NOLOCK(&dtmf_frames);
 
-	AST_RWLIST_WRLOCK(&aslist);
+	AST_LIST_LOCK(&aslist);
 
 	/* Save the autoservice channel list state.  We _must_ verify that the channel
 	 * list has been rebuilt before we return.  Because, after we return, the channel
@@ -226,9 +235,9 @@ int ast_autoservice_stop(struct ast_channel *chan)
 	 * it after its gone! */
 	chan_list_state = as_chan_list_state;
 
-	AST_RWLIST_TRAVERSE_SAFE_BEGIN(&aslist, as, list) {	
+	AST_LIST_TRAVERSE_SAFE_BEGIN(&aslist, as, list) {	
 		if (as->chan == chan) {
-			AST_RWLIST_REMOVE_CURRENT(list);
+			AST_LIST_REMOVE_CURRENT(list);
 			as->use_count--;
 			if (as->use_count)
 				break;
@@ -241,12 +250,12 @@ int ast_autoservice_stop(struct ast_channel *chan)
 			break;
 		}
 	}
-	AST_RWLIST_TRAVERSE_SAFE_END;
+	AST_LIST_TRAVERSE_SAFE_END;
 
 	if (removed && asthread != AST_PTHREADT_NULL) 
 		pthread_kill(asthread, SIGURG);
 	
-	AST_RWLIST_UNLOCK(&aslist);
+	AST_LIST_UNLOCK(&aslist);
 
 	if (!removed)
 		return 0;
@@ -268,3 +277,8 @@ int ast_autoservice_stop(struct ast_channel *chan)
 
 	return res;
 }
+
+void ast_autoservice_init(void)
+{
+	ast_cond_init(&as_cond, NULL);
+}