Messages in this thread Patch in this message | | | From | Jiri Slaby <> | Subject | [PATCH 3/3] sound: dummy, avoid races with timer | Date | Mon, 19 Jan 2015 10:42:56 +0100 |
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There is a race between timer and process contexts. Process context does not disable irqs, so when a timer ticks inside process' critical section, the system can deadlock. Fix this by a traditional _irqsave variant of spin_lock.
Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Jaroslav Kysela <perex@perex.cz> Cc: Takashi Iwai <tiwai@suse.de> Cc: alsa-devel@alsa-project.org --- sound/drivers/dummy.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c index 6d6bf4093583..18a7cfc99078 100644 --- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -271,10 +271,13 @@ static void dummy_systimer_update(struct dummy_systimer_pcm *dpcm) static int dummy_systimer_start(struct snd_pcm_substream *substream) { struct dummy_systimer_pcm *dpcm = substream->runtime->private_data; - spin_lock(&dpcm->lock); + unsigned long flags; + + spin_lock_irqsave(&dpcm->lock, flags); dpcm->base_time = jiffies; dummy_systimer_rearm(dpcm); - spin_unlock(&dpcm->lock); + spin_unlock_irqrestore(&dpcm->lock, flags); + return 0; } @@ -322,12 +325,14 @@ static snd_pcm_uframes_t dummy_systimer_pointer(struct snd_pcm_substream *substream) { struct dummy_systimer_pcm *dpcm = substream->runtime->private_data; + unsigned long flags; snd_pcm_uframes_t pos; - spin_lock(&dpcm->lock); + spin_lock_irqsave(&dpcm->lock, flags); dummy_systimer_update(dpcm); pos = dpcm->frac_pos / HZ; - spin_unlock(&dpcm->lock); + spin_unlock_irqrestore(&dpcm->lock, flags); + return pos; } -- 2.2.1
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