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Fixes locking inversion issue in ast_async_goto()

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During this function we can not hold the "chan" lock while
doing the masquerade, the explicit goto on the tmp chan, or
the channel alloc.  Instead we need to get the channel lock,
store off information about the channel that we need, and
then let the channel lock go for the remainder of the function.

Review: https://reviewboard.asterisk.org/r/1275/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@324364 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
David Vossel
2011-06-21 20:11:52 +00:00
parent a9a8c0fa05
commit 87908a3f5d
2 changed files with 70 additions and 41 deletions
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109
main/pbx.c
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@@ -7818,55 +7818,82 @@ int ast_explicit_goto(struct ast_channel *chan, const char *context, const char
int ast_async_goto(struct ast_channel *chan, const char *context, const char *exten, int priority)
{
int res = 0;
struct ast_channel *tmpchan;
struct {
char *accountcode;
char *exten;
char *context;
char *linkedid;
char *name;
struct ast_cdr *cdr;
int amaflags;
int state;
format_t readformat;
format_t writeformat;
} tmpvars = { 0, };
ast_channel_lock(chan);
if (chan->pbx) { /* This channel is currently in the PBX */
ast_explicit_goto(chan, context, exten, priority + 1);
ast_softhangup_nolock(chan, AST_SOFTHANGUP_ASYNCGOTO);
} else {
/* In order to do it when the channel doesn't really exist within
the PBX, we have to make a new channel, masquerade, and start the PBX
at the new location */
struct ast_channel *tmpchan = ast_channel_alloc(0, chan->_state, 0, 0, chan->accountcode, chan->exten, chan->context, chan->linkedid, chan->amaflags, "AsyncGoto/%s", chan->name);
if (!tmpchan) {
res = -1;
} else {
if (chan->cdr) {
ast_cdr_discard(tmpchan->cdr);
tmpchan->cdr = ast_cdr_dup(chan->cdr); /* share the love */
}
/* Make formats okay */
tmpchan->readformat = chan->readformat;
tmpchan->writeformat = chan->writeformat;
/* Setup proper location */
ast_explicit_goto(tmpchan,
S_OR(context, chan->context), S_OR(exten, chan->exten), priority);
ast_channel_unlock(chan);
return res;
}
/* Masquerade into temp channel */
if (ast_channel_masquerade(tmpchan, chan)) {
/* Failed to set up the masquerade. It's probably chan_local
* in the middle of optimizing itself out. Sad. :( */
ast_hangup(tmpchan);
tmpchan = NULL;
res = -1;
} else {
/* it may appear odd to unlock chan here since the masquerade is on
* tmpchan, but no channel locks should be held when doing a masquerade
* since a masquerade requires a lock on the channels ao2 container. */
ast_channel_unlock(chan);
ast_do_masquerade(tmpchan);
ast_channel_lock(chan);
/* Start the PBX going on our stolen channel */
if (ast_pbx_start(tmpchan)) {
ast_log(LOG_WARNING, "Unable to start PBX on %s\n", tmpchan->name);
ast_hangup(tmpchan);
res = -1;
}
}
/* In order to do it when the channel doesn't really exist within
* the PBX, we have to make a new channel, masquerade, and start the PBX
* at the new location */
tmpvars.accountcode = ast_strdupa(chan->accountcode);
tmpvars.exten = ast_strdupa(chan->exten);
tmpvars.context = ast_strdupa(chan->context);
tmpvars.linkedid = ast_strdupa(chan->linkedid);
tmpvars.name = ast_strdupa(chan->name);
tmpvars.amaflags = chan->amaflags;
tmpvars.state = chan->_state;
tmpvars.writeformat = chan->writeformat;
tmpvars.readformat = chan->readformat;
tmpvars.cdr = chan->cdr ? ast_cdr_dup(chan->cdr) : NULL;
ast_channel_unlock(chan);
/* Do not hold any channel locks while calling channel_alloc() since the function
* locks the channel container when linking the new channel in. */
if (!(tmpchan = ast_channel_alloc(0, tmpvars.state, 0, 0, tmpvars.accountcode, tmpvars.exten, tmpvars.context, tmpvars.linkedid, tmpvars.amaflags, "AsyncGoto/%s", tmpvars.name))) {
ast_cdr_discard(tmpvars.cdr);
return -1;
}
/* copy the cdr info over */
if (tmpvars.cdr) {
ast_cdr_discard(tmpchan->cdr);
tmpchan->cdr = tmpvars.cdr;
tmpvars.cdr = NULL;
}
/* Make formats okay */
tmpchan->readformat = tmpvars.readformat;
tmpchan->writeformat = tmpvars.writeformat;
/* Setup proper location. Never hold another channel lock while calling this function. */
ast_explicit_goto(tmpchan, S_OR(context, tmpvars.context), S_OR(exten, tmpvars.exten), priority);
/* Masquerade into tmp channel */
if (ast_channel_masquerade(tmpchan, chan)) {
/* Failed to set up the masquerade. It's probably chan_local
* in the middle of optimizing itself out. Sad. :( */
ast_hangup(tmpchan);
tmpchan = NULL;
res = -1;
} else {
ast_do_masquerade(tmpchan);
/* Start the PBX going on our stolen channel */
if (ast_pbx_start(tmpchan)) {
ast_log(LOG_WARNING, "Unable to start PBX on %s\n", tmpchan->name);
ast_hangup(tmpchan);
res = -1;
}
}
ast_channel_unlock(chan);
return res;
}