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Remove some redundant locking code in ast_do_masquerade().

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Also updated some comments.


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@330368 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Richard Mudgett
2011-07-30 23:56:29 +00:00
parent 842ab32ecc
commit 4bd9b75724
1 changed files with 26 additions and 23 deletions
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49
main/channel.c
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@@ -6299,37 +6299,40 @@ int ast_do_masquerade(struct ast_channel *original)
*/
ao2_lock(channels);
/* lock the original channel to determine if the masquerade is require or not */
/* lock the original channel to determine if the masquerade is required or not */
ast_channel_lock(original);
/* This checks to see if the masquerade has already happened or not. There is a
* race condition that exists for this function. Since all pvt and channel locks
* must be let go before calling do_masquerade, it is possible that it could be
* called multiple times for the same channel. This check verifies whether
* or not the masquerade has already been completed by another thread */
if (!original->masq) {
ast_channel_unlock(original);
ao2_unlock(channels);
return 0; /* masq already completed by another thread, or never needed to be done to begin with */
}
/* now that we have verified no race condition exists, set the clone channel */
clonechan = original->masq;
/* since this function already holds the global container lock, unlocking original
* for deadlock avoidance will not result in any sort of masquerade race condition.
* If masq is called by a different thread while this happens, it will be stuck waiting
* until we unlock the container. */
/*
* This checks to see if the masquerade has already happened or
* not. There is a race condition that exists for this
* function. Since all pvt and channel locks must be let go
* before calling do_masquerade, it is possible that it could be
* called multiple times for the same channel. This check
* verifies whether or not the masquerade has already been
* completed by another thread.
*/
while ((clonechan = original->masq) && ast_channel_trylock(clonechan)) {
/*
* A masq is needed but we could not get the clonechan lock
* immediately. Since this function already holds the global
* container lock, unlocking original for deadlock avoidance
* will not result in any sort of masquerade race condition. If
* masq is called by a different thread while this happens, it
* will be stuck waiting until we unlock the container.
*/
CHANNEL_DEADLOCK_AVOIDANCE(original);
}
/* recheck if masq has been done the deadlock avoidance above could cause a double masq
* this is posible with at least ast_hangup*/
if (!original->masq) {
/*
* A final masq check must be done after deadlock avoidance for
* clonechan above or we could get a double masq. This is
* posible with ast_hangup at least.
*/
if (!clonechan) {
/* masq already completed by another thread, or never needed to be done to begin with */
ast_channel_unlock(original);
ao2_unlock(channels);
return 0; /* masq already completed by another thread, or never needed to be done to begin with */
return 0;
}
/* Get any transfer masquerade connected line exchange data. */