On Wed, 13 Apr 2016 12:42:01 +0200, Andreas x Larsson wrote:
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
Isn't this dependent on gcc version?
And, if we use the gcc atomic operation, the whole macros should be rewritten in another way -- or consider to drop the whole. It's only partly used in pcm_rate.c and pcm_plugin.c in anyway.
thanks,
Takashi
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)
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