sysmocom
/
asterisk
11
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

moh: fix a refcount error with realtime MOH 

I observed a crash in res_musiconhold on an Asterisk 11 system using realtime
MOH.  Investigation of the backtrace showed a corrupt mohclass, implying that
it got destroyed before the code expected it to.  I went looking for reference
counting errors that could have caused this crash and this patch this result.
It contains 2 changes.

1) Remove a usless block of code that was impossible to reach.  There was even
a comment indicating that it was impossible to reach.  The conditional includes
"!ast_test_flag(global_flags, MOH_CACHERTCLASSES)" and it's inside of an if
block with the opposite check "ast_test_flag(global_flags,
MOH_CACHERTCLASSES)".  There's no good reason to keep it around.

2) A similar block to #1 contained a reference counting error.  It stores
state->class in the local variable mohclass without increasing its reference
count.  The reference count on mohclass is decremented at the end of the
function.  This block of code probably very rarely runs, which would help
explain why this system was working fine for many months before experiencing a
crash.

Review: https://reviewboard.asterisk.org/r/3282/
........

Merged revisions 410043 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 410044 from http://svn.asterisk.org/svn/asterisk/branches/11
........

Merged revisions 410090 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@410091 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Russell Bryant 2014-03-06 23:43:34 +00:00
parent a4906e9f86
commit fbf8700c10
1 changed files with 1 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
res/res_musiconhold.c
View File

@ -1486,12 +1486,6 @@ static int local_ast_moh_start(struct ast_channel *chan, const char *mclass, con
if (state && state->class) {
/* Class already exist for this channel */
ast_log(LOG_NOTICE, "This channel already has a MOH class attached (%s)!\n", state->class->name);
if (state->class->realtime && !ast_test_flag(global_flags, MOH_CACHERTCLASSES) && !strcasecmp(mohclass->name, state->class->name)) {
/* we found RT class with the same name, seems like we should continue playing existing one */
/* XXX This code is impossible to reach */
mohclass = mohclass_unref(mohclass, "unreffing potential mohclass (channel already has a class)");
mohclass = state->class;
}
}
/* We don't want moh_register to unref the mohclass because we do it at the end of this function as well.
* If we allowed moh_register to unref the mohclass,too, then the count would be off by one. The result would
@ -1544,7 +1538,7 @@ static int local_ast_moh_start(struct ast_channel *chan, const char *mclass, con
if (state->class->realtime && !ast_test_flag(global_flags, MOH_CACHERTCLASSES) && !strcasecmp(mohclass->name, state->class->name)) {
/* we found RT class with the same name, seems like we should continue playing existing one */
mohclass = mohclass_unref(mohclass, "unreffing potential mohclass (channel already has one)");
mohclass = state->class;
mohclass = mohclass_ref(state->class, "using existing class from state");
}
} else {
if (ast_pthread_create_background(&mohclass->thread, NULL, monmp3thread, mohclass)) {