Under some usecases a race condition appears inside the snd_atomic_write_* functions. The 'begin' and 'end' variables are updated with the ++ operator which is not atomic but needs to be. This can be achieved with the gcc atomic_* built-ins. Combined with __ATOMIC_SEQ_CST as the memory model, memory barriers are introduced so those can also be removed from the code.
Signed-off-by: Andreas x Larsson andrelan@axis.com Signed-off-by: Arvid Nihlgård Lindell arvidnl@axis.com --- alsa-lib/include/iatomic.h | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/alsa-lib/include/iatomic.h b/alsa-lib/include/iatomic.h index acdd3e2..7fafe20 100644 --- a/alsa-lib/include/iatomic.h +++ b/alsa-lib/include/iatomic.h @@ -140,14 +140,12 @@ static __inline__ void snd_atomic_write_init(snd_atomic_write_t *w)
static __inline__ void snd_atomic_write_begin(snd_atomic_write_t *w) { - w->begin++; - wmb(); + __atomic_add_fetch(&w->begin, 1,__ATOMIC_SEQ_CST); }
static __inline__ void snd_atomic_write_end(snd_atomic_write_t *w) { - wmb(); - w->end++; + __atomic_add_fetch(&w->end, 1, __ATOMIC_SEQ_CST); }
static __inline__ void snd_atomic_read_init(snd_atomic_read_t *r, snd_atomic_write_t *w)