[alsa-devel] [PATCH 23/25] ALSA/dummy: Replace tasklet with softirq hrtimer
From: Thomas Gleixner tglx@linutronix.de
The tasklet is used to defer the execution of snd_pcm_period_elapsed() to the softirq context. Using the CLOCK_MONOTONIC_SOFT base invokes the timer callback in softirq context as well which renders the tasklet useless.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Anna-Maria Gleixner anna-maria@linutronix.de Cc: Jaroslav Kysela perex@perex.cz Cc: Takashi Iwai tiwai@suse.com Cc: Takashi Sakamoto o-takashi@sakamocchi.jp Cc: alsa-devel@alsa-project.org --- sound/drivers/dummy.c | 16 +++------------- 1 file changed, 3 insertions(+), 13 deletions(-)
--- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -376,17 +376,9 @@ struct dummy_hrtimer_pcm { ktime_t period_time; atomic_t running; struct hrtimer timer; - struct tasklet_struct tasklet; struct snd_pcm_substream *substream; };
-static void dummy_hrtimer_pcm_elapsed(unsigned long priv) -{ - struct dummy_hrtimer_pcm *dpcm = (struct dummy_hrtimer_pcm *)priv; - if (atomic_read(&dpcm->running)) - snd_pcm_period_elapsed(dpcm->substream); -} - static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) { struct dummy_hrtimer_pcm *dpcm; @@ -394,7 +386,8 @@ static enum hrtimer_restart dummy_hrtime dpcm = container_of(timer, struct dummy_hrtimer_pcm, timer); if (!atomic_read(&dpcm->running)) return HRTIMER_NORESTART; - tasklet_schedule(&dpcm->tasklet); + + snd_pcm_period_elapsed(dpcm->substream); hrtimer_forward_now(timer, dpcm->period_time); return HRTIMER_RESTART; } @@ -421,7 +414,6 @@ static int dummy_hrtimer_stop(struct snd static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm) { hrtimer_cancel(&dpcm->timer); - tasklet_kill(&dpcm->tasklet); }
static snd_pcm_uframes_t @@ -466,12 +458,10 @@ static int dummy_hrtimer_create(struct s if (!dpcm) return -ENOMEM; substream->runtime->private_data = dpcm; - hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC_SOFT, HRTIMER_MODE_REL); dpcm->timer.function = dummy_hrtimer_callback; dpcm->substream = substream; atomic_set(&dpcm->running, 0); - tasklet_init(&dpcm->tasklet, dummy_hrtimer_pcm_elapsed, - (unsigned long)dpcm); return 0; }
Hi,
On Aug 31 2017 21:23, Anna-Maria Gleixner wrote:
From: Thomas Gleixner tglx@linutronix.de
The tasklet is used to defer the execution of snd_pcm_period_elapsed() to the softirq context. Using the CLOCK_MONOTONIC_SOFT base invokes the timer callback in softirq context as well which renders the tasklet useless.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Anna-Maria Gleixner anna-maria@linutronix.de Cc: Jaroslav Kysela perex@perex.cz Cc: Takashi Iwai tiwai@suse.com Cc: Takashi Sakamoto o-takashi@sakamocchi.jp Cc: alsa-devel@alsa-project.org
sound/drivers/dummy.c | 16 +++------------- 1 file changed, 3 insertions(+), 13 deletions(-)
I prefer this patch as long as this driver can still receive callbacks from hrtimer subsystem.
Reviewed-by: Takashi Sakamoto o-takashi@sakamocchi.jp
Unfortunately, I have too poor machine to compile whole kernel now, thus didn't do any tests, sorry.
I note that ALSA pcsp driver uses a combination of hrtimer/tasklet for the same purpose. I think we can simplify it, too. Please refer to a patch in the end of this message. (But not tested yet for the above reason...)
--- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -376,17 +376,9 @@ struct dummy_hrtimer_pcm { ktime_t period_time; atomic_t running; struct hrtimer timer;
- struct tasklet_struct tasklet; struct snd_pcm_substream *substream;
};
-static void dummy_hrtimer_pcm_elapsed(unsigned long priv) -{
- struct dummy_hrtimer_pcm *dpcm = (struct dummy_hrtimer_pcm *)priv;
- if (atomic_read(&dpcm->running))
snd_pcm_period_elapsed(dpcm->substream);-}
static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) { struct dummy_hrtimer_pcm *dpcm; @@ -394,7 +386,8 @@ static enum hrtimer_restart dummy_hrtime dpcm = container_of(timer, struct dummy_hrtimer_pcm, timer); if (!atomic_read(&dpcm->running)) return HRTIMER_NORESTART;
- tasklet_schedule(&dpcm->tasklet);
- snd_pcm_period_elapsed(dpcm->substream); hrtimer_forward_now(timer, dpcm->period_time); return HRTIMER_RESTART;
} @@ -421,7 +414,6 @@ static int dummy_hrtimer_stop(struct snd static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm) { hrtimer_cancel(&dpcm->timer);
- tasklet_kill(&dpcm->tasklet);
}
static snd_pcm_uframes_t @@ -466,12 +458,10 @@ static int dummy_hrtimer_create(struct s if (!dpcm) return -ENOMEM; substream->runtime->private_data = dpcm;
- hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
- hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC_SOFT, HRTIMER_MODE_REL); dpcm->timer.function = dummy_hrtimer_callback; dpcm->substream = substream; atomic_set(&dpcm->running, 0);
- tasklet_init(&dpcm->tasklet, dummy_hrtimer_pcm_elapsed,
(unsigned long)dpcm);}
From b2417f83e0ccbdfe1fc6870817ff0a1bd9243c77 Mon Sep 17 00:00:00 2001
From: Takashi Sakamoto o-takashi@sakamocchi.jp Date: Thu, 31 Aug 2017 22:52:33 +0900 Subject: [PATCH] ALSA: pcsp: code optimization for hrtimer in software IRQ context
In a development period for v4.14, code refactoring was done for hrtimer subsystem. This enables to receive callbacks from hrtimer in software IRQ context.
Currently, ALSA pcsp driver uses hrtimer callback to handle period elapse of PCM buffer and actual calculation of pointer position is done in software IRQ context of tasklet. This can be simplified to the introduced hrtimer in software IRQ context.
This commit applies an optimization for the above reason.
Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp --- sound/drivers/pcsp/pcsp.c | 2 +- sound/drivers/pcsp/pcsp_lib.c | 24 +++++------------------- 2 files changed, 6 insertions(+), 20 deletions(-)
diff --git a/sound/drivers/pcsp/pcsp.c b/sound/drivers/pcsp/pcsp.c index 0dd3f46eb03e..8fac38b81c4f 100644 --- a/sound/drivers/pcsp/pcsp.c +++ b/sound/drivers/pcsp/pcsp.c @@ -100,7 +100,7 @@ static int snd_card_pcsp_probe(int devnum, struct device *dev) if (devnum != 0) return -EINVAL;
- hrtimer_init(&pcsp_chip.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + hrtimer_init(&pcsp_chip.timer, CLOCK_MONOTONIC_SOFT, HRTIMER_MODE_REL); pcsp_chip.timer.function = pcsp_do_timer;
err = snd_card_new(dev, index, id, THIS_MODULE, 0, &card); diff --git a/sound/drivers/pcsp/pcsp_lib.c b/sound/drivers/pcsp/pcsp_lib.c index 2f5a35f38ce1..d2b67463ddd3 100644 --- a/sound/drivers/pcsp/pcsp_lib.c +++ b/sound/drivers/pcsp/pcsp_lib.c @@ -21,22 +21,6 @@ MODULE_PARM_DESC(nforce_wa, "Apply NForce chipset workaround "
#define DMIX_WANTS_S16 1
-/* - * Call snd_pcm_period_elapsed in a tasklet - * This avoids spinlock messes and long-running irq contexts - */ -static void pcsp_call_pcm_elapsed(unsigned long priv) -{ - if (atomic_read(&pcsp_chip.timer_active)) { - struct snd_pcm_substream *substream; - substream = pcsp_chip.playback_substream; - if (substream) - snd_pcm_period_elapsed(substream); - } -} - -static DECLARE_TASKLET(pcsp_pcm_tasklet, pcsp_call_pcm_elapsed, 0); - /* write the port and returns the next expire time in ns; * called at the trigger-start and in hrtimer callback */ @@ -121,8 +105,11 @@ static void pcsp_pointer_update(struct snd_pcsp *chip) } spin_unlock_irqrestore(&chip->substream_lock, flags);
- if (periods_elapsed) - tasklet_schedule(&pcsp_pcm_tasklet); + if (!periods_elapsed) + return; + + if (atomic_read(&pcsp_chip.timer_active)) + snd_pcm_period_elapsed(substream); }
enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle) @@ -195,7 +182,6 @@ void pcsp_sync_stop(struct snd_pcsp *chip) pcsp_stop_playing(chip); local_irq_enable(); hrtimer_cancel(&chip->timer); - tasklet_kill(&pcsp_pcm_tasklet); }
static int snd_pcsp_playback_close(struct snd_pcm_substream *substream)
On Thu, 31 Aug 2017 16:21:17 +0200, Takashi Sakamoto wrote:
Hi,
On Aug 31 2017 21:23, Anna-Maria Gleixner wrote:
From: Thomas Gleixner tglx@linutronix.de
The tasklet is used to defer the execution of snd_pcm_period_elapsed() to the softirq context. Using the CLOCK_MONOTONIC_SOFT base invokes the timer callback in softirq context as well which renders the tasklet useless.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Anna-Maria Gleixner anna-maria@linutronix.de Cc: Jaroslav Kysela perex@perex.cz Cc: Takashi Iwai tiwai@suse.com Cc: Takashi Sakamoto o-takashi@sakamocchi.jp Cc: alsa-devel@alsa-project.org
sound/drivers/dummy.c | 16 +++------------- 1 file changed, 3 insertions(+), 13 deletions(-)
I prefer this patch as long as this driver can still receive callbacks from hrtimer subsystem.
Reviewed-by: Takashi Sakamoto o-takashi@sakamocchi.jp
Unfortunately, I have too poor machine to compile whole kernel now, thus didn't do any tests, sorry.
I note that ALSA pcsp driver uses a combination of hrtimer/tasklet for the same purpose. I think we can simplify it, too. Please refer to a patch in the end of this message. (But not tested yet for the above reason...)
The pcsp is a bit special. It's really high frequent irq calls for controlling the beep on/off, thus offloading the whole isn't good.
thanks,
Takashi
On Thu, 31 Aug 2017 14:23:45 +0200, Anna-Maria Gleixner wrote:
From: Thomas Gleixner tglx@linutronix.de
The tasklet is used to defer the execution of snd_pcm_period_elapsed() to the softirq context. Using the CLOCK_MONOTONIC_SOFT base invokes the timer callback in softirq context as well which renders the tasklet useless.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Anna-Maria Gleixner anna-maria@linutronix.de Cc: Jaroslav Kysela perex@perex.cz Cc: Takashi Iwai tiwai@suse.com Cc: Takashi Sakamoto o-takashi@sakamocchi.jp Cc: alsa-devel@alsa-project.org
I gave it at try, but it caused a kernel hang, unfortunately.
The reason is that snd_pcm_period_elapased() may stop the stream (e.g. when reaching at the end). With this patchset, it'll lead to the call of hrtimer_cancel() from the hrtimer callback itself, thus it stalls.
Below is the additional fix over your patch for working around it. I believe it should cover most corner cases, and seems working fine through quick tests, so far.
thanks,
Takashi
--- diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c index 273d60c42125..b5dd64e3dab1 100644 --- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -375,6 +375,7 @@ struct dummy_hrtimer_pcm { ktime_t base_time; ktime_t period_time; atomic_t running; + atomic_t callback_running; struct hrtimer timer; struct snd_pcm_substream *substream; }; @@ -387,8 +388,15 @@ static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) if (!atomic_read(&dpcm->running)) return HRTIMER_NORESTART;
+ atomic_inc(&dpcm->callback_running); snd_pcm_period_elapsed(dpcm->substream); + atomic_dec(&dpcm->callback_running); + /* may be flipped during snd_pcm_period_elapsed() */ + if (!atomic_read(&dpcm->running)) + return HRTIMER_NORESTART; + hrtimer_forward_now(timer, dpcm->period_time); + atomic_dec(&dpcm->callback_running); return HRTIMER_RESTART; }
@@ -407,7 +415,9 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream) struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
atomic_set(&dpcm->running, 0); - hrtimer_cancel(&dpcm->timer); + /* issue hrtimer_cancel() only when called outside the callback */ + if (!atomic_read(&dpcm->callback_running)) + hrtimer_cancel(&dpcm->timer); return 0; }
@@ -462,6 +472,7 @@ static int dummy_hrtimer_create(struct snd_pcm_substream *substream) dpcm->timer.function = dummy_hrtimer_callback; dpcm->substream = substream; atomic_set(&dpcm->running, 0); + atomic_set(&dpcm->callback_running, 0); return 0; }
Hi,
On Sep 1 2017 00:36, Takashi Iwai wrote:
I gave it at try, but it caused a kernel hang, unfortunately.
The reason is that snd_pcm_period_elapased() may stop the stream (e.g. when reaching at the end). With this patchset, it'll lead to the call of hrtimer_cancel() from the hrtimer callback itself, thus it stalls.
I can reproduce this bug.
Below is the additional fix over your patch for working around it. I believe it should cover most corner cases, and seems working fine through quick tests, so far.
This patch looks good to me, too. But I have an alternative.
We can use 'hrtimer_callback_running()' to detect whether to be on hrtimer callback or not (please read '__run_hrtimer()' in 'kernel/time/hrtimer.c'). Usage of this helper function on .stop callback to skip cancellation can avoid the stall. In this case, after stopping PCM substream, the hrtimer callback should return HRTIMER_NORESTART to avoid restarting, as well as your patch. Please test a patch in this message.
diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c index 273d60c42125..b5dd64e3dab1 100644 --- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -375,6 +375,7 @@ struct dummy_hrtimer_pcm { ktime_t base_time; ktime_t period_time; atomic_t running;
- atomic_t callback_running; struct hrtimer timer; struct snd_pcm_substream *substream; };
@@ -387,8 +388,15 @@ static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) if (!atomic_read(&dpcm->running)) return HRTIMER_NORESTART;
- atomic_inc(&dpcm->callback_running); snd_pcm_period_elapsed(dpcm->substream);
- atomic_dec(&dpcm->callback_running);
- /* may be flipped during snd_pcm_period_elapsed() */
- if (!atomic_read(&dpcm->running))
return HRTIMER_NORESTART;- hrtimer_forward_now(timer, dpcm->period_time);
- atomic_dec(&dpcm->callback_running); return HRTIMER_RESTART; }
@@ -407,7 +415,9 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream) struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
atomic_set(&dpcm->running, 0);
- hrtimer_cancel(&dpcm->timer);
- /* issue hrtimer_cancel() only when called outside the callback */
- if (!atomic_read(&dpcm->callback_running))
hrtimer_cancel(&dpcm->timer);@@ -462,6 +472,7 @@ static int dummy_hrtimer_create(struct snd_pcm_substream *substream) dpcm->timer.function = dummy_hrtimer_callback; dpcm->substream = substream; atomic_set(&dpcm->running, 0);
- atomic_set(&dpcm->callback_running, 0); return 0; }
From 07d61ba2a1c0e06e914443225e194d99f2d8c58d Mon Sep 17 00:00:00 2001
From: Takashi Sakamoto o-takashi@sakamocchi.jp Date: Fri, 1 Sep 2017 19:10:18 +0900 Subject: [PATCH] ALSA: dummy: avoid stall due to a call of hrtimer_cancel() on a callback of hrtimer
A call of 'htrimer_cancel()' on a callback of hrtimer brings endless loop because 'struct hrtimer_clock_base.running' is not NULL on the callback. In hrtimer subsystem, this member is used to indicate the instance of hrtimer gets callbacks and there's a helper function, 'hrtimer_callback_running()' to check it.
ALSA dummy driver uses hrtimer to emulate hardware interrupt per period of PCM buffer. When XRUN occurs on PCM substream, in a call of 'snd_pcm_period_elapsed()', 'struct snd_pcm_ops.stop()' is called to stop the substream. In current implementation, 'hrtimer_cancel()' is used to wait for cancellation of hrtimer. However, as described, this brings endless loop.
For this problem, this commit uses 'hrtimer_callback_running()' to detect whether to be on a callback of hrtimer or not, then skip cancellation of hrtimer in hrtimer callbacks. Furthermore, at a case of XRUN, hrtimer callback returns HRTIMER_NORESTART after a call of 'snd_pcm_period_elapsed()' to discontinue hrtimr because cancellation is skipped.
Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp --- sound/drivers/dummy.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c index 273d60c42125..9caf754c6135 100644 --- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -387,7 +387,11 @@ static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) if (!atomic_read(&dpcm->running)) return HRTIMER_NORESTART;
+ /* In a case of XRUN, this calls .trigger to stop PCM substream. */ snd_pcm_period_elapsed(dpcm->substream); + if (!atomic_read(&dpcm->running)) + return HRTIMER_NORESTART; + hrtimer_forward_now(timer, dpcm->period_time); return HRTIMER_RESTART; } @@ -407,7 +411,8 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream) struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
atomic_set(&dpcm->running, 0); - hrtimer_cancel(&dpcm->timer); + if (!hrtimer_callback_running(&dpcm->timer)) + hrtimer_cancel(&dpcm->timer); return 0; }
On Fri, 01 Sep 2017 12:25:37 +0200, Takashi Sakamoto wrote:
Hi,
On Sep 1 2017 00:36, Takashi Iwai wrote:
I gave it at try, but it caused a kernel hang, unfortunately.
The reason is that snd_pcm_period_elapased() may stop the stream (e.g. when reaching at the end). With this patchset, it'll lead to the call of hrtimer_cancel() from the hrtimer callback itself, thus it stalls.
I can reproduce this bug.
Below is the additional fix over your patch for working around it. I believe it should cover most corner cases, and seems working fine through quick tests, so far.
This patch looks good to me, too. But I have an alternative.
We can use 'hrtimer_callback_running()' to detect whether to be on hrtimer callback or not (please read '__run_hrtimer()' in 'kernel/time/hrtimer.c').
A good point, this is a better choice.
Usage of this helper function on .stop callback to skip cancellation can avoid the stall. In this case, after stopping PCM substream, the hrtimer callback should return HRTIMER_NORESTART to avoid restarting, as well as your patch. Please test a patch in this message.
diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c index 273d60c42125..b5dd64e3dab1 100644 --- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -375,6 +375,7 @@ struct dummy_hrtimer_pcm { ktime_t base_time; ktime_t period_time; atomic_t running;
- atomic_t callback_running; struct hrtimer timer; struct snd_pcm_substream *substream; };
@@ -387,8 +388,15 @@ static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) if (!atomic_read(&dpcm->running)) return HRTIMER_NORESTART;
- atomic_inc(&dpcm->callback_running); snd_pcm_period_elapsed(dpcm->substream);
- atomic_dec(&dpcm->callback_running);
- /* may be flipped during snd_pcm_period_elapsed() */
- if (!atomic_read(&dpcm->running))
return HRTIMER_NORESTART;- hrtimer_forward_now(timer, dpcm->period_time);
- atomic_dec(&dpcm->callback_running); return HRTIMER_RESTART; }
@@ -407,7 +415,9 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream) struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
atomic_set(&dpcm->running, 0);
- hrtimer_cancel(&dpcm->timer);
- /* issue hrtimer_cancel() only when called outside the callback */
- if (!atomic_read(&dpcm->callback_running))
hrtimer_cancel(&dpcm->timer);@@ -462,6 +472,7 @@ static int dummy_hrtimer_create(struct snd_pcm_substream *substream) dpcm->timer.function = dummy_hrtimer_callback; dpcm->substream = substream; atomic_set(&dpcm->running, 0);
- atomic_set(&dpcm->callback_running, 0); return 0; }
From 07d61ba2a1c0e06e914443225e194d99f2d8c58d Mon Sep 17 00:00:00 2001
From: Takashi Sakamoto o-takashi@sakamocchi.jp Date: Fri, 1 Sep 2017 19:10:18 +0900 Subject: [PATCH] ALSA: dummy: avoid stall due to a call of hrtimer_cancel() on a callback of hrtimer
A call of 'htrimer_cancel()' on a callback of hrtimer brings endless loop because 'struct hrtimer_clock_base.running' is not NULL on the callback. In hrtimer subsystem, this member is used to indicate the instance of hrtimer gets callbacks and there's a helper function, 'hrtimer_callback_running()' to check it.
ALSA dummy driver uses hrtimer to emulate hardware interrupt per period of PCM buffer. When XRUN occurs on PCM substream, in a call of 'snd_pcm_period_elapsed()', 'struct snd_pcm_ops.stop()' is called to stop the substream. In current implementation, 'hrtimer_cancel()' is used to wait for cancellation of hrtimer. However, as described, this brings endless loop.
It's not only about XRUN. When the stream finishes the draining, it stops the stream gracefully -- that is the very normal operation.
For this problem, this commit uses 'hrtimer_callback_running()' to detect whether to be on a callback of hrtimer or not, then skip cancellation of hrtimer in hrtimer callbacks. Furthermore, at a case of XRUN, hrtimer callback returns HRTIMER_NORESTART after a call of 'snd_pcm_period_elapsed()' to discontinue hrtimr because cancellation is skipped.
Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp
It's better to fold the fix into the original patch instead of introducing a bug and fixing it.
Takashi
On p 1 2017 20:58, Takashi Iwai wrote:
From 07d61ba2a1c0e06e914443225e194d99f2d8c58d Mon Sep 17 00:00:00 2001
From: Takashi Sakamoto o-takashi@sakamocchi.jp Date: Fri, 1 Sep 2017 19:10:18 +0900 Subject: [PATCH] ALSA: dummy: avoid stall due to a call of hrtimer_cancel() on a callback of hrtimer
A call of 'htrimer_cancel()' on a callback of hrtimer brings endless loop because 'struct hrtimer_clock_base.running' is not NULL on the callback. In hrtimer subsystem, this member is used to indicate the instance of hrtimer gets callbacks and there's a helper function, 'hrtimer_callback_running()' to check it.
ALSA dummy driver uses hrtimer to emulate hardware interrupt per period of PCM buffer. When XRUN occurs on PCM substream, in a call of 'snd_pcm_period_elapsed()', 'struct snd_pcm_ops.stop()' is called to stop the substream. In current implementation, 'hrtimer_cancel()' is used to wait for cancellation of hrtimer. However, as described, this brings endless loop.
It's not only about XRUN. When the stream finishes the draining, it stops the stream gracefully -- that is the very normal operation.
I overlooked it. Thanks for your indication.
For this problem, this commit uses 'hrtimer_callback_running()' to detect whether to be on a callback of hrtimer or not, then skip cancellation of hrtimer in hrtimer callbacks. Furthermore, at a case of XRUN, hrtimer callback returns HRTIMER_NORESTART after a call of 'snd_pcm_period_elapsed()' to discontinue hrtimr because cancellation is skipped.
Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp
It's better to fold the fix into the original patch instead of introducing a bug and fixing it.
Yep. I request the authors to include this fix.
Well, in sound subsystem, there're a few drivers which uses hrtimer: - snd-pcsp - snd-sh-dac-audio - snd-soc-imx-pcm-fiq
As a quick glance, 'snd-sh-dac-audio' includes the same bug, too. Additionally, 'snd-soc-imx-pcm-fiq' maintains hrtimer with loose manner in a point of state of PCM substream and it shall gain the same bug if improved. Later, I posted some patches for them.
Thanks
Takashi Sakamoto
Hi,
On Sep 2 2017 10:19, Takashi Sakamoto wrote:
Well, in sound subsystem, there're a few drivers which uses hrtimer:
- snd-pcsp
- snd-sh-dac-audio
- snd-soc-imx-pcm-fiq
As a quick glance, 'snd-sh-dac-audio' includes the same bug, too. Additionally, 'snd-soc-imx-pcm-fiq' maintains hrtimer with loose manner in a point of state of PCM substream and it shall gain the same bug if improved. Later, I posted some patches for them.
After reading code thoroughly, I conclude that no need to fix these two drivers. They're programmed with own protections. The former (snd-sh-dac-audio) has 'struct snd_sh_dac.empty' and the latter (snd-soc-imx-pcm-fiq) has 'struct imx_pcm_runtime_data.playing' and '.capturing', to avoid cancellation of hrtimer on hrtimer callback.
These ways are not necessarily efficient but actually have no trouble. I leave them as is.
Regards
Takashi Sakamoto
From: Thomas Gleixner tglx@linutronix.de
The tasklet is used to defer the execution of snd_pcm_period_elapsed() to the softirq context. Using the CLOCK_MONOTONIC_SOFT base invokes the timer callback in softirq context as well which renders the tasklet useless.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Anna-Maria Gleixner anna-maria@linutronix.de Cc: Jaroslav Kysela perex@perex.cz Cc: Takashi Iwai tiwai@suse.com Cc: Takashi Sakamoto o-takashi@sakamocchi.jp Cc: alsa-devel@alsa-project.org [o-takashi: avoid stall due to a call of hrtimer_cancel() on a callback of hrtimer] Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de --- On 2017-09-02 10:19:45 [+0900], Takashi Sakamoto wrote:
Yep. I request the authors to include this
Thank you for providing a fix.
v1…v2: merged Takashi Sakamoto fixup of the original patch into v2.
So this patch now is okay?
sound/drivers/dummy.c | 23 +++++++++-------------- 1 file changed, 9 insertions(+), 14 deletions(-)
diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c index dd5ed037adf2..3d01fe17ed36 100644 --- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -376,17 +376,9 @@ struct dummy_hrtimer_pcm { ktime_t period_time; atomic_t running; struct hrtimer timer; - struct tasklet_struct tasklet; struct snd_pcm_substream *substream; };
-static void dummy_hrtimer_pcm_elapsed(unsigned long priv) -{ - struct dummy_hrtimer_pcm *dpcm = (struct dummy_hrtimer_pcm *)priv; - if (atomic_read(&dpcm->running)) - snd_pcm_period_elapsed(dpcm->substream); -} - static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) { struct dummy_hrtimer_pcm *dpcm; @@ -394,7 +386,12 @@ static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) dpcm = container_of(timer, struct dummy_hrtimer_pcm, timer); if (!atomic_read(&dpcm->running)) return HRTIMER_NORESTART; - tasklet_schedule(&dpcm->tasklet); + + /* In a case of XRUN, this calls .trigger to stop PCM substream. */ + snd_pcm_period_elapsed(dpcm->substream); + if (!atomic_read(&dpcm->running)) + return HRTIMER_NORESTART; + hrtimer_forward_now(timer, dpcm->period_time); return HRTIMER_RESTART; } @@ -414,14 +411,14 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream) struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
atomic_set(&dpcm->running, 0); - hrtimer_cancel(&dpcm->timer); + if (!hrtimer_callback_running(&dpcm->timer)) + hrtimer_cancel(&dpcm->timer); return 0; }
static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm) { hrtimer_cancel(&dpcm->timer); - tasklet_kill(&dpcm->tasklet); }
static snd_pcm_uframes_t @@ -466,12 +463,10 @@ static int dummy_hrtimer_create(struct snd_pcm_substream *substream) if (!dpcm) return -ENOMEM; substream->runtime->private_data = dpcm; - hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC_SOFT, HRTIMER_MODE_REL); dpcm->timer.function = dummy_hrtimer_callback; dpcm->substream = substream; atomic_set(&dpcm->running, 0); - tasklet_init(&dpcm->tasklet, dummy_hrtimer_pcm_elapsed, - (unsigned long)dpcm); return 0; }
On Tue, 05 Sep 2017 17:53:51 +0200, Sebastian Andrzej Siewior wrote:
From: Thomas Gleixner tglx@linutronix.de
The tasklet is used to defer the execution of snd_pcm_period_elapsed() to the softirq context. Using the CLOCK_MONOTONIC_SOFT base invokes the timer callback in softirq context as well which renders the tasklet useless.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Anna-Maria Gleixner anna-maria@linutronix.de Cc: Jaroslav Kysela perex@perex.cz Cc: Takashi Iwai tiwai@suse.com Cc: Takashi Sakamoto o-takashi@sakamocchi.jp Cc: alsa-devel@alsa-project.org [o-takashi: avoid stall due to a call of hrtimer_cancel() on a callback of hrtimer] Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de
On 2017-09-02 10:19:45 [+0900], Takashi Sakamoto wrote:
Yep. I request the authors to include this
Thank you for providing a fix.
v1…v2: merged Takashi Sakamoto fixup of the original patch into v2.
So this patch now is okay?
Note that you can try it by yourself easily, as it's a dummy driver that doesn't need anything special. Just run aplay for that device (e.g. aplay -Dplughw:2 for card#2) can reproduce the original problem.
@@ -394,7 +386,12 @@ static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) dpcm = container_of(timer, struct dummy_hrtimer_pcm, timer); if (!atomic_read(&dpcm->running)) return HRTIMER_NORESTART;
- tasklet_schedule(&dpcm->tasklet);
- /* In a case of XRUN, this calls .trigger to stop PCM substream. */
As mentioned, the stop happens not only with XRUN but also in a normal situation by draining.
Other than that, looks OK to me (but not tested it).
thanks,
Takashi
- snd_pcm_period_elapsed(dpcm->substream);
- if (!atomic_read(&dpcm->running))
return HRTIMER_NORESTART;- hrtimer_forward_now(timer, dpcm->period_time); return HRTIMER_RESTART;
} @@ -414,14 +411,14 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream) struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
atomic_set(&dpcm->running, 0);
- hrtimer_cancel(&dpcm->timer);
- if (!hrtimer_callback_running(&dpcm->timer))
hrtimer_cancel(&dpcm->timer);}
static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm) { hrtimer_cancel(&dpcm->timer);
- tasklet_kill(&dpcm->tasklet);
}
static snd_pcm_uframes_t @@ -466,12 +463,10 @@ static int dummy_hrtimer_create(struct snd_pcm_substream *substream) if (!dpcm) return -ENOMEM; substream->runtime->private_data = dpcm;
- hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
- hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC_SOFT, HRTIMER_MODE_REL); dpcm->timer.function = dummy_hrtimer_callback; dpcm->substream = substream; atomic_set(&dpcm->running, 0);
- tasklet_init(&dpcm->tasklet, dummy_hrtimer_pcm_elapsed,
(unsigned long)dpcm);}
-- 2.14.1
On Sep 6 2017 00:53, Sebastian Andrzej Siewior wrote:
From: Thomas Gleixner tglx@linutronix.de
The tasklet is used to defer the execution of snd_pcm_period_elapsed() to the softirq context. Using the CLOCK_MONOTONIC_SOFT base invokes the timer callback in softirq context as well which renders the tasklet useless.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Anna-Maria Gleixner anna-maria@linutronix.de Cc: Jaroslav Kysela perex@perex.cz Cc: Takashi Iwai tiwai@suse.com Cc: Takashi Sakamoto o-takashi@sakamocchi.jp Cc: alsa-devel@alsa-project.org [o-takashi: avoid stall due to a call of hrtimer_cancel() on a callback of hrtimer] Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de
On 2017-09-02 10:19:45 [+0900], Takashi Sakamoto wrote:
Yep. I request the authors to include this
Thank you for providing a fix.
v1…v2: merged Takashi Sakamoto fixup of the original patch into v2.
So this patch now is okay?
I have a small nitpick.
sound/drivers/dummy.c | 23 +++++++++-------------- 1 file changed, 9 insertions(+), 14 deletions(-)
diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c index dd5ed037adf2..3d01fe17ed36 100644 --- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -376,17 +376,9 @@ struct dummy_hrtimer_pcm { ktime_t period_time; atomic_t running; struct hrtimer timer;
- struct tasklet_struct tasklet; struct snd_pcm_substream *substream; };
-static void dummy_hrtimer_pcm_elapsed(unsigned long priv) -{
- struct dummy_hrtimer_pcm *dpcm = (struct dummy_hrtimer_pcm *)priv;
- if (atomic_read(&dpcm->running))
snd_pcm_period_elapsed(dpcm->substream);-}
- static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) { struct dummy_hrtimer_pcm *dpcm;
@@ -394,7 +386,12 @@ static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) dpcm = container_of(timer, struct dummy_hrtimer_pcm, timer); if (!atomic_read(&dpcm->running)) return HRTIMER_NORESTART;
- tasklet_schedule(&dpcm->tasklet);
- /* In a case of XRUN, this calls .trigger to stop PCM substream. */
As Iwai-san mentioned, in this function, .trigger can be called in two cases; XRUN occurs and draining is done. Thus, let you change the comment as 'In cases of XRUN and draining, this calls .trigger to stop PCM substream.'. I'm sorry to trouble you.
snd_pcm_period_elapsed() ->snd_pcm_update_hw_ptr0() ->snd_pcm_update_state() ->snd_pcm_drain_done() ... ->.trigger(TRIGGER_STOP) ->xrun() ->snd_pcm_stop() ... ->.trigger(TRIGGER_STOP)
- snd_pcm_period_elapsed(dpcm->substream);
- if (!atomic_read(&dpcm->running))
return HRTIMER_NORESTART;- hrtimer_forward_now(timer, dpcm->period_time); return HRTIMER_RESTART; }
@@ -414,14 +411,14 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream) struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
atomic_set(&dpcm->running, 0);
- hrtimer_cancel(&dpcm->timer);
if (!hrtimer_callback_running(&dpcm->timer))
hrtimer_cancel(&dpcm->timer);return 0; }
static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm) { hrtimer_cancel(&dpcm->timer);
tasklet_kill(&dpcm->tasklet); }
static snd_pcm_uframes_t
@@ -466,12 +463,10 @@ static int dummy_hrtimer_create(struct snd_pcm_substream *substream) if (!dpcm) return -ENOMEM; substream->runtime->private_data = dpcm;
- hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
- hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC_SOFT, HRTIMER_MODE_REL); dpcm->timer.function = dummy_hrtimer_callback; dpcm->substream = substream; atomic_set(&dpcm->running, 0);
- tasklet_init(&dpcm->tasklet, dummy_hrtimer_pcm_elapsed,
(unsigned long)dpcm);
Regards
Takashi Sakamoto
From: Thomas Gleixner tglx@linutronix.de
The tasklet is used to defer the execution of snd_pcm_period_elapsed() to the softirq context. Using the CLOCK_MONOTONIC_SOFT base invokes the timer callback in softirq context as well which renders the tasklet useless.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Anna-Maria Gleixner anna-maria@linutronix.de Cc: Jaroslav Kysela perex@perex.cz Cc: Takashi Iwai tiwai@suse.com Cc: Takashi Sakamoto o-takashi@sakamocchi.jp Cc: alsa-devel@alsa-project.org [o-takashi: avoid stall due to a call of hrtimer_cancel() on a callback of hrtimer] Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de --- On 2017-09-06 01:05:43 [+0900], Takashi Sakamoto wrote:
As Iwai-san mentioned, in this function, .trigger can be called in two cases; XRUN occurs and draining is done. Thus, let you change the comment as 'In cases of XRUN and draining, this calls .trigger to stop PCM substream.'. I'm sorry to trouble you.
snd_pcm_period_elapsed() ->snd_pcm_update_hw_ptr0() ->snd_pcm_update_state() ->snd_pcm_drain_done() ... ->.trigger(TRIGGER_STOP) ->xrun() ->snd_pcm_stop() ... ->.trigger(TRIGGER_STOP)
I think you asked me just to update the comment. Did I do it right?
v2…v3: updated the comment as per Takashi Sakamoto's suggestion. v1…v2: merged Takashi Sakamoto fixup of the original patch into v2.
sound/drivers/dummy.c | 25 +++++++++++-------------- 1 file changed, 11 insertions(+), 14 deletions(-)
diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c index dd5ed037adf2..cdd851286f92 100644 --- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -376,17 +376,9 @@ struct dummy_hrtimer_pcm { ktime_t period_time; atomic_t running; struct hrtimer timer; - struct tasklet_struct tasklet; struct snd_pcm_substream *substream; };
-static void dummy_hrtimer_pcm_elapsed(unsigned long priv) -{ - struct dummy_hrtimer_pcm *dpcm = (struct dummy_hrtimer_pcm *)priv; - if (atomic_read(&dpcm->running)) - snd_pcm_period_elapsed(dpcm->substream); -} - static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) { struct dummy_hrtimer_pcm *dpcm; @@ -394,7 +386,14 @@ static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) dpcm = container_of(timer, struct dummy_hrtimer_pcm, timer); if (!atomic_read(&dpcm->running)) return HRTIMER_NORESTART; - tasklet_schedule(&dpcm->tasklet); + /* + * In cases of XRUN and draining, this calls .trigger to stop PCM + * substream. + */ + snd_pcm_period_elapsed(dpcm->substream); + if (!atomic_read(&dpcm->running)) + return HRTIMER_NORESTART; + hrtimer_forward_now(timer, dpcm->period_time); return HRTIMER_RESTART; } @@ -414,14 +413,14 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream) struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
atomic_set(&dpcm->running, 0); - hrtimer_cancel(&dpcm->timer); + if (!hrtimer_callback_running(&dpcm->timer)) + hrtimer_cancel(&dpcm->timer); return 0; }
static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm) { hrtimer_cancel(&dpcm->timer); - tasklet_kill(&dpcm->tasklet); }
static snd_pcm_uframes_t @@ -466,12 +465,10 @@ static int dummy_hrtimer_create(struct snd_pcm_substream *substream) if (!dpcm) return -ENOMEM; substream->runtime->private_data = dpcm; - hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC_SOFT, HRTIMER_MODE_REL); dpcm->timer.function = dummy_hrtimer_callback; dpcm->substream = substream; atomic_set(&dpcm->running, 0); - tasklet_init(&dpcm->tasklet, dummy_hrtimer_pcm_elapsed, - (unsigned long)dpcm); return 0; }
On Sep 6 2017 01:18, Sebastian Andrzej Siewior wrote:
From: Thomas Gleixner tglx@linutronix.de
The tasklet is used to defer the execution of snd_pcm_period_elapsed() to the softirq context. Using the CLOCK_MONOTONIC_SOFT base invokes the timer callback in softirq context as well which renders the tasklet useless.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Anna-Maria Gleixner anna-maria@linutronix.de Cc: Jaroslav Kysela perex@perex.cz Cc: Takashi Iwai tiwai@suse.com Cc: Takashi Sakamoto o-takashi@sakamocchi.jp Cc: alsa-devel@alsa-project.org [o-takashi: avoid stall due to a call of hrtimer_cancel() on a callback of hrtimer] Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de
On 2017-09-06 01:05:43 [+0900], Takashi Sakamoto wrote:
As Iwai-san mentioned, in this function, .trigger can be called in two cases; XRUN occurs and draining is done. Thus, let you change the comment as 'In cases of XRUN and draining, this calls .trigger to stop PCM substream.'. I'm sorry to trouble you.
snd_pcm_period_elapsed() ->snd_pcm_update_hw_ptr0() ->snd_pcm_update_state() ->snd_pcm_drain_done() ... ->.trigger(TRIGGER_STOP) ->xrun() ->snd_pcm_stop() ... ->.trigger(TRIGGER_STOP)
I think you asked me just to update the comment. Did I do it right?
v2…v3: updated the comment as per Takashi Sakamoto's suggestion. v1…v2: merged Takashi Sakamoto fixup of the original patch into v2.
sound/drivers/dummy.c | 25 +++++++++++-------------- 1 file changed, 11 insertions(+), 14 deletions(-)
This Looks good to me. I did quick test and confirmed that it brings no stalls.
Tested-by: Takashi Sakamoto o-takashi@sakamocchi.jp
diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c index dd5ed037adf2..cdd851286f92 100644 --- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -376,17 +376,9 @@ struct dummy_hrtimer_pcm { ktime_t period_time; atomic_t running; struct hrtimer timer;
- struct tasklet_struct tasklet; struct snd_pcm_substream *substream; };
-static void dummy_hrtimer_pcm_elapsed(unsigned long priv) -{
- struct dummy_hrtimer_pcm *dpcm = (struct dummy_hrtimer_pcm *)priv;
- if (atomic_read(&dpcm->running))
snd_pcm_period_elapsed(dpcm->substream);-}
- static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) { struct dummy_hrtimer_pcm *dpcm;
@@ -394,7 +386,14 @@ static enum hrtimer_restart dummy_hrtimer_callback(struct hrtimer *timer) dpcm = container_of(timer, struct dummy_hrtimer_pcm, timer); if (!atomic_read(&dpcm->running)) return HRTIMER_NORESTART;
- tasklet_schedule(&dpcm->tasklet);
- /*
* In cases of XRUN and draining, this calls .trigger to stop PCM* substream.*/- snd_pcm_period_elapsed(dpcm->substream);
- if (!atomic_read(&dpcm->running))
return HRTIMER_NORESTART;- hrtimer_forward_now(timer, dpcm->period_time); return HRTIMER_RESTART; }
@@ -414,14 +413,14 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream) struct dummy_hrtimer_pcm *dpcm = substream->runtime->private_data;
atomic_set(&dpcm->running, 0);
- hrtimer_cancel(&dpcm->timer);
if (!hrtimer_callback_running(&dpcm->timer))
hrtimer_cancel(&dpcm->timer);return 0; }
static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm) { hrtimer_cancel(&dpcm->timer);
tasklet_kill(&dpcm->tasklet); }
static snd_pcm_uframes_t
@@ -466,12 +465,10 @@ static int dummy_hrtimer_create(struct snd_pcm_substream *substream) if (!dpcm) return -ENOMEM; substream->runtime->private_data = dpcm;
- hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
- hrtimer_init(&dpcm->timer, CLOCK_MONOTONIC_SOFT, HRTIMER_MODE_REL); dpcm->timer.function = dummy_hrtimer_callback; dpcm->substream = substream; atomic_set(&dpcm->running, 0);
- tasklet_init(&dpcm->tasklet, dummy_hrtimer_pcm_elapsed,
(unsigned long)dpcm);
Thanks
Takashi Sakamoto
On Wed, 06 Sep 2017 06:30:03 +0200, Takashi Sakamoto wrote:
On Sep 6 2017 01:18, Sebastian Andrzej Siewior wrote:
From: Thomas Gleixner tglx@linutronix.de
The tasklet is used to defer the execution of snd_pcm_period_elapsed() to the softirq context. Using the CLOCK_MONOTONIC_SOFT base invokes the timer callback in softirq context as well which renders the tasklet useless.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Anna-Maria Gleixner anna-maria@linutronix.de Cc: Jaroslav Kysela perex@perex.cz Cc: Takashi Iwai tiwai@suse.com Cc: Takashi Sakamoto o-takashi@sakamocchi.jp Cc: alsa-devel@alsa-project.org [o-takashi: avoid stall due to a call of hrtimer_cancel() on a callback of hrtimer] Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de
On 2017-09-06 01:05:43 [+0900], Takashi Sakamoto wrote:
As Iwai-san mentioned, in this function, .trigger can be called in two cases; XRUN occurs and draining is done. Thus, let you change the comment as 'In cases of XRUN and draining, this calls .trigger to stop PCM substream.'. I'm sorry to trouble you.
snd_pcm_period_elapsed() ->snd_pcm_update_hw_ptr0() ->snd_pcm_update_state() ->snd_pcm_drain_done() ... ->.trigger(TRIGGER_STOP) ->xrun() ->snd_pcm_stop() ... ->.trigger(TRIGGER_STOP)
I think you asked me just to update the comment. Did I do it right?
v2…v3: updated the comment as per Takashi Sakamoto's suggestion. v1…v2: merged Takashi Sakamoto fixup of the original patch into v2.
sound/drivers/dummy.c | 25 +++++++++++-------------- 1 file changed, 11 insertions(+), 14 deletions(-)
This Looks good to me. I did quick test and confirmed that it brings no stalls.
Tested-by: Takashi Sakamoto o-takashi@sakamocchi.jp
I suppose you'd apply all together in some tree like tip or whatever? In anyway, feel free to take my ack for this patch: Reviewed-by: Takashi Iwai tiwai@suse.de
Thanks!
Takashi
participants (4)
-
Anna-Maria Gleixner -
Sebastian Andrzej Siewior -
Takashi Iwai -
Takashi Sakamoto