lkml.org 
[lkml]   [2015]   [Jan]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 3/3] sound: dummy, avoid races with timer
Date
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


\
 
 \ /
  Last update: 2015-01-19 11:01    [W:0.111 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site