* [alsa-devel] [RFC PATCH] ALSA: pcm: fix blocking while loop in snd_pcm_update_hw_ptr0()
@ 2019-10-23 12:01 Srinivas Kandagatla
2019-10-23 13:29 ` Takashi Iwai
0 siblings, 1 reply; 2+ messages in thread
From: Srinivas Kandagatla @ 2019-10-23 12:01 UTC (permalink / raw)
To: broonie, tiwai
Cc: alsa-devel, bgoswami, spapothi, Preetam Singh Ranawat, vkoul,
Srinivas Kandagatla
From: Preetam Singh Ranawat <apranawat@codeaurora.org>
When period interrupts are disabled, while loop in snd_pcm_update_hw_ptr0()
results in the machine locking up if runtime->hw_ptr_buffer_jiffies is 0.
Validate runtime->hw_ptr_buffer_jiffies value before while loop to avoid
delta check.
Signed-off-by: Preetam Singh Ranawat <apranawat@codeaurora.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
---
This issue was noticed in Android setup from fastcapture path.
sound/core/pcm_lib.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index d80041ea4e01..f407f6895f8a 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -341,7 +341,8 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
* the elapsed time to detect xruns.
*/
jdelta = curr_jiffies - runtime->hw_ptr_jiffies;
- if (jdelta < runtime->hw_ptr_buffer_jiffies / 2)
+ if ((jdelta < runtime->hw_ptr_buffer_jiffies / 2) ||
+ !runtime->hw_ptr_buffer_jiffies)
goto no_delta_check;
hdelta = jdelta - delta * HZ / runtime->rate;
xrun_threshold = runtime->hw_ptr_buffer_jiffies / 2 + 1;
--
2.21.0
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^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [alsa-devel] [RFC PATCH] ALSA: pcm: fix blocking while loop in snd_pcm_update_hw_ptr0()
2019-10-23 12:01 [alsa-devel] [RFC PATCH] ALSA: pcm: fix blocking while loop in snd_pcm_update_hw_ptr0() Srinivas Kandagatla
@ 2019-10-23 13:29 ` Takashi Iwai
0 siblings, 0 replies; 2+ messages in thread
From: Takashi Iwai @ 2019-10-23 13:29 UTC (permalink / raw)
To: Srinivas Kandagatla
Cc: alsa-devel, bgoswami, spapothi, tiwai, Preetam Singh Ranawat,
vkoul, broonie
On Wed, 23 Oct 2019 14:01:14 +0200,
Srinivas Kandagatla wrote:
>
> From: Preetam Singh Ranawat <apranawat@codeaurora.org>
>
> When period interrupts are disabled, while loop in snd_pcm_update_hw_ptr0()
> results in the machine locking up if runtime->hw_ptr_buffer_jiffies is 0.
>
> Validate runtime->hw_ptr_buffer_jiffies value before while loop to avoid
> delta check.
Although the fix itself is fine, I still wonder how this is
triggered. Could you check in what kind of PCM state is it?
Basically snd_pcm_update_hw_ptr*() is called only in the running PCM
state, and for that, we should have set hw_ptr_buffer_jiffies at
snd_pcm_post_start(). It's
runtime->hw_ptr_buffer_jiffies = (runtime->buffer_size * HZ) /
runtime->rate;
So maybe the given buffer size is so small and hw_ptr_buffer_jiffies
is really 0?
thanks,
Takashi
>
> Signed-off-by: Preetam Singh Ranawat <apranawat@codeaurora.org>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> ---
>
> This issue was noticed in Android setup from fastcapture path.
>
> sound/core/pcm_lib.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
> index d80041ea4e01..f407f6895f8a 100644
> --- a/sound/core/pcm_lib.c
> +++ b/sound/core/pcm_lib.c
> @@ -341,7 +341,8 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
> * the elapsed time to detect xruns.
> */
> jdelta = curr_jiffies - runtime->hw_ptr_jiffies;
> - if (jdelta < runtime->hw_ptr_buffer_jiffies / 2)
> + if ((jdelta < runtime->hw_ptr_buffer_jiffies / 2) ||
> + !runtime->hw_ptr_buffer_jiffies)
> goto no_delta_check;
> hdelta = jdelta - delta * HZ / runtime->rate;
> xrun_threshold = runtime->hw_ptr_buffer_jiffies / 2 + 1;
> --
> 2.21.0
>
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2019-10-23 12:01 [alsa-devel] [RFC PATCH] ALSA: pcm: fix blocking while loop in snd_pcm_update_hw_ptr0() Srinivas Kandagatla
2019-10-23 13:29 ` Takashi Iwai
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