Stop timer in the 'hw_free' callback instead of the 'close' callback
since we want the timer to be stopped before the DMA buffer is released.
Otherwise, it could trigger a kernel panic in some circumstances, for
instance when the DMA buffer is already released but the timer callback
is still running.
Signed-off-by: Ivan Orlov <[email protected]>
---
V1 -> V2:
- Remove useless NULLing of v_iter->substream. It will be released in
'close' callback.
sound/drivers/pcmtest.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/sound/drivers/pcmtest.c b/sound/drivers/pcmtest.c
index b59b78a09224..8a78fa56106f 100644
--- a/sound/drivers/pcmtest.c
+++ b/sound/drivers/pcmtest.c
@@ -396,8 +396,6 @@ static int snd_pcmtst_pcm_close(struct snd_pcm_substream *substream)
{
struct pcmtst_buf_iter *v_iter = substream->runtime->private_data;
- timer_shutdown_sync(&v_iter->timer_instance);
- v_iter->substream = NULL;
playback_capture_test = !v_iter->is_buf_corrupted;
kfree(v_iter);
return 0;
@@ -499,6 +497,10 @@ static int snd_pcmtst_pcm_hw_params(struct snd_pcm_substream *substream,
static int snd_pcmtst_pcm_hw_free(struct snd_pcm_substream *substream)
{
+ struct pcmtst_buf_iter *v_iter = substream->runtime->private_data;
+
+ timer_shutdown_sync(&v_iter->timer_instance);
+
return 0;
}
--
2.34.1
On Wed, 06 Dec 2023 16:10:46 +0100,
Ivan Orlov wrote:
>
> Stop timer in the 'hw_free' callback instead of the 'close' callback
> since we want the timer to be stopped before the DMA buffer is released.
> Otherwise, it could trigger a kernel panic in some circumstances, for
> instance when the DMA buffer is already released but the timer callback
> is still running.
You can't call timer_shutdown_sync() at hw_free. The PCM stream is
still there and you can re-setup via hw_params without closing. But,
after timer_shutdown_sync(), the timer instance must not be used any
longer.
A more proper way would be to call timer_delete() (no sync) at trigger
STOP, then call timer_delete_sync() at sync_stop op in addition. This
assures the immediate stop and the sync before changing to another PCM
state.
timer_shutdown_sync() can be kept at the close op to be sure.
thanks,
Takashi
>
> Signed-off-by: Ivan Orlov <[email protected]>
> ---
> V1 -> V2:
> - Remove useless NULLing of v_iter->substream. It will be released in
> 'close' callback.
>
> sound/drivers/pcmtest.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/sound/drivers/pcmtest.c b/sound/drivers/pcmtest.c
> index b59b78a09224..8a78fa56106f 100644
> --- a/sound/drivers/pcmtest.c
> +++ b/sound/drivers/pcmtest.c
> @@ -396,8 +396,6 @@ static int snd_pcmtst_pcm_close(struct snd_pcm_substream *substream)
> {
> struct pcmtst_buf_iter *v_iter = substream->runtime->private_data;
>
> - timer_shutdown_sync(&v_iter->timer_instance);
> - v_iter->substream = NULL;
> playback_capture_test = !v_iter->is_buf_corrupted;
> kfree(v_iter);
> return 0;
> @@ -499,6 +497,10 @@ static int snd_pcmtst_pcm_hw_params(struct snd_pcm_substream *substream,
>
> static int snd_pcmtst_pcm_hw_free(struct snd_pcm_substream *substream)
> {
> + struct pcmtst_buf_iter *v_iter = substream->runtime->private_data;
> +
> + timer_shutdown_sync(&v_iter->timer_instance);
> +
> return 0;
> }
>
> --
> 2.34.1
>
On 12/6/23 16:59, Takashi Iwai wrote:
> On Wed, 06 Dec 2023 16:10:46 +0100,
> Ivan Orlov wrote:
>>
>> Stop timer in the 'hw_free' callback instead of the 'close' callback
>> since we want the timer to be stopped before the DMA buffer is released.
>> Otherwise, it could trigger a kernel panic in some circumstances, for
>> instance when the DMA buffer is already released but the timer callback
>> is still running.
>
> You can't call timer_shutdown_sync() at hw_free. The PCM stream is
> still there and you can re-setup via hw_params without closing. But,
> after timer_shutdown_sync(), the timer instance must not be used any
> longer.
>
> A more proper way would be to call timer_delete() (no sync) at trigger
> STOP, then call timer_delete_sync() at sync_stop op in addition. This
> assures the immediate stop and the sync before changing to another PCM
> state.
>
> timer_shutdown_sync() can be kept at the close op to be sure.
>
>
> thanks,
>
> Takashi
>
Hi Takashi,
Thanks a lot for the review, sounds reasonable, I'll make suggested
changes and send the version 3 :)
--
Kind regards,
Ivan Orlov