From 3b74246b1695f319dcb2022caff67f0b50aba9dd Mon Sep 17 00:00:00 2001 From: Moises Silva Date: Mon, 24 Oct 2011 12:43:54 -0400 Subject: [PATCH] freetdm: * Avoid acquiring the span mutex if the pendingchans queue is available for use * * FreeTDM modules using the old FTDM_SPAN_STATE_CHANGE flag should be updated * * until then, they are still vulnerable to deadlock situations * * Modules pending update: (ftmod_analog, ftmod_libpri, ftmod_isdn) * * Fixes Sangoma redmine ticket #1791 0 FTDM span stop deadlock * --- libs/freetdm/src/ftdm_state.c | 13 ++++++++++--- libs/freetdm/src/include/private/ftdm_types.h | 6 ++++++ 2 files changed, 16 insertions(+), 3 deletions(-) diff --git a/libs/freetdm/src/ftdm_state.c b/libs/freetdm/src/ftdm_state.c index 54ecde530d..d3f99f6074 100644 --- a/libs/freetdm/src/ftdm_state.c +++ b/libs/freetdm/src/ftdm_state.c @@ -370,12 +370,19 @@ end: } ftdm_set_flag(ftdmchan, FTDM_CHANNEL_STATE_CHANGE); - ftdm_mutex_lock(ftdmchan->span->mutex); - ftdm_set_flag(ftdmchan->span, FTDM_SPAN_STATE_CHANGE); if (ftdmchan->span->pendingchans) { ftdm_queue_enqueue(ftdmchan->span->pendingchans, ftdmchan); + } else { + /* there is a potential deadlock here, if a signaling module is processing + * state changes while the ftdm_span_stop() function is called, the signaling + * thread will block until it can acquire the span lock, but the thread calling + * ftdm_span_stop() which holds the span lock is waiting on the signaling thread + * to finish ... The only reason to acquire the span lock is this flag, new + * signaling modules should use the pendingchans queue instead of this flag, + * as of today a few modules need still to be updated before we can get rid of + * this flag (ie, ftmod_libpri, ftmod_isdn, ftmod_analog) */ + ftdm_set_flag_locked(ftdmchan->span, FTDM_SPAN_STATE_CHANGE); } - ftdm_mutex_unlock(ftdmchan->span->mutex); if (ftdm_test_flag(ftdmchan, FTDM_CHANNEL_NONBLOCK)) { /* the channel should not block waiting for state processing */ diff --git a/libs/freetdm/src/include/private/ftdm_types.h b/libs/freetdm/src/include/private/ftdm_types.h index 2ed9fd04c5..6df25fe4d2 100755 --- a/libs/freetdm/src/include/private/ftdm_types.h +++ b/libs/freetdm/src/include/private/ftdm_types.h @@ -173,6 +173,12 @@ typedef enum { FTDM_SPAN_SUSPENDED = (1 << 3), FTDM_SPAN_IN_THREAD = (1 << 4), FTDM_SPAN_STOP_THREAD = (1 << 5), + /*! Signaling modules set this flag to use fchan->pendingchans queue instead + * of the FTDM_SPAN_STATE_CHANGE flag to detect when there is channels with + * a state change pending in the span. If you set this member you can't rely + * on FTDM_SPAN_STATE_CHANGE anymore and must use the queue only instead. This + * is the new way of detecting state changes, new modules should always set this + * flag, the old modules still relying on FTDM_SPAN_STATE_CHANGE should be updated */ FTDM_SPAN_USE_CHAN_QUEUE = (1 << 6), FTDM_SPAN_SUGGEST_CHAN_ID = (1 << 7), FTDM_SPAN_USE_AV_RATE = (1 << 8),