This fixes a deadlock when using the pcm_jack plugin via a plug.
Some snd_pcm_ioplug_* functions assumed that they were being called with the pcm mutex locked, and would perform an unlock-act-lock sequence in order to allow the relevant function to lock the mutex itself.
If the mutex was not locked before calling these functions, it would silently fail on unlocking the mutex, and then erroneously leave the mutex locked as it left the function.
This patch checks to see if the mutex is locked before attempting the unlock-act-lock sequence. If the mutex is not locked when entering these functions, then we act and leave the mutex unlocked.
Signed-off-by: Ben Russell thematrixeatsyou@gmail.com --- src/pcm/pcm_ioplug.c | 50 +++++++++++++++++++++++++++++++------------- 1 file changed, 35 insertions(+), 15 deletions(-)
diff --git a/src/pcm/pcm_ioplug.c b/src/pcm/pcm_ioplug.c index a437ca32..a94ecd96 100644 --- a/src/pcm/pcm_ioplug.c +++ b/src/pcm/pcm_ioplug.c @@ -164,9 +164,13 @@ static int snd_pcm_ioplug_prepare(snd_pcm_t *pcm)
snd_pcm_ioplug_reset(pcm); if (io->data->callback->prepare) { - snd_pcm_unlock(pcm); /* to avoid deadlock */ - err = io->data->callback->prepare(io->data); - snd_pcm_lock(pcm); + if (snd_pcm_is_locked(pcm)) { + snd_pcm_unlock(pcm); /* to avoid deadlock */ + err = io->data->callback->prepare(io->data); + snd_pcm_lock(pcm); + } else { + err = io->data->callback->prepare(io->data); + } } if (err < 0) return err; @@ -463,9 +467,13 @@ static int snd_pcm_ioplug_sw_params(snd_pcm_t *pcm, snd_pcm_sw_params_t *params) if (!io->data->callback->sw_params) return 0;
- snd_pcm_unlock(pcm); /* to avoid deadlock */ - err = io->data->callback->sw_params(io->data, params); - snd_pcm_lock(pcm); + if (snd_pcm_is_locked(pcm)) { + snd_pcm_unlock(pcm); /* to avoid deadlock */ + err = io->data->callback->sw_params(io->data, params); + snd_pcm_lock(pcm); + } else { + err = io->data->callback->sw_params(io->data, params); + }
return err; } @@ -764,9 +772,13 @@ static int snd_pcm_ioplug_poll_descriptors_count(snd_pcm_t *pcm) int err = 1;
if (io->data->callback->poll_descriptors_count) { - snd_pcm_unlock(pcm); /* to avoid deadlock */ - err = io->data->callback->poll_descriptors_count(io->data); - snd_pcm_lock(pcm); + if (snd_pcm_is_locked(pcm)) { + snd_pcm_unlock(pcm); /* to avoid deadlock */ + err = io->data->callback->poll_descriptors_count(io->data); + snd_pcm_lock(pcm); + } else { + err = io->data->callback->poll_descriptors_count(io->data); + } } return err; } @@ -777,9 +789,13 @@ static int snd_pcm_ioplug_poll_descriptors(snd_pcm_t *pcm, struct pollfd *pfds, int err;
if (io->data->callback->poll_descriptors) { - snd_pcm_unlock(pcm); /* to avoid deadlock */ - err = io->data->callback->poll_descriptors(io->data, pfds, space); - snd_pcm_lock(pcm); + if (snd_pcm_is_locked(pcm)) { + snd_pcm_unlock(pcm); /* to avoid deadlock */ + err = io->data->callback->poll_descriptors(io->data, pfds, space); + snd_pcm_lock(pcm); + } else { + err = io->data->callback->poll_descriptors(io->data, pfds, space); + } return err; } if (pcm->poll_fd < 0) @@ -799,9 +815,13 @@ static int snd_pcm_ioplug_poll_revents(snd_pcm_t *pcm, struct pollfd *pfds, unsi int err;
if (io->data->callback->poll_revents) { - snd_pcm_unlock(pcm); /* to avoid deadlock */ - err = io->data->callback->poll_revents(io->data, pfds, nfds, revents); - snd_pcm_lock(pcm); + if (snd_pcm_is_locked(pcm)) { + snd_pcm_unlock(pcm); /* to avoid deadlock */ + err = io->data->callback->poll_revents(io->data, pfds, nfds, revents); + snd_pcm_lock(pcm); + } else { + err = io->data->callback->poll_revents(io->data, pfds, nfds, revents); + } } else { *revents = pfds->revents; err = 0;