From 96c7d478efad594e483ee8a826395b1342404885 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Mon, 11 Aug 2008 10:18:39 +0200 Subject: ALSA: pcsp - Fix locking messes in snd-pcsp snd-pcsp driver takes chip->substream_lock together with PCM substream lock. These are even mixed up with hrtimer's lock, resulting in messy lock depencies. Right now, snd-pcsp driver resolves the deadlock by using HRTIMER_CB_SOFTIRQ. However, this isn't nice for a really fast path like bit-flipping. This patch introduces a tasklet for PCM period handling so that the hrtimer callback can be handled fast. This also reduce the use of chip->substream_lock to avoid deadlocks. It's still used in pointer callback, but even this could be removed with a proper barrier. Another good solution is to introduce async trigger callback. But, this will involve with a major rewrite of the PCM core code, so I take first this easy fix. Signed-off-by: Takashi Iwai --- sound/drivers/pcsp/pcsp.c | 8 ++-- sound/drivers/pcsp/pcsp.h | 1 + sound/drivers/pcsp/pcsp_lib.c | 95 +++++++++++++++++++++++-------------------- 3 files changed, 56 insertions(+), 48 deletions(-) (limited to 'sound/drivers/pcsp') diff --git a/sound/drivers/pcsp/pcsp.c b/sound/drivers/pcsp/pcsp.c index 1899cf0685bc..87219bf0a35e 100644 --- a/sound/drivers/pcsp/pcsp.c +++ b/sound/drivers/pcsp/pcsp.c @@ -96,7 +96,7 @@ static int __devinit snd_card_pcsp_probe(int devnum, struct device *dev) return -EINVAL; hrtimer_init(&pcsp_chip.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); - pcsp_chip.timer.cb_mode = HRTIMER_CB_SOFTIRQ; + pcsp_chip.timer.cb_mode = HRTIMER_CB_IRQSAFE; pcsp_chip.timer.function = pcsp_do_timer; card = snd_card_new(index, id, THIS_MODULE, 0); @@ -188,10 +188,8 @@ static int __devexit pcsp_remove(struct platform_device *dev) static void pcsp_stop_beep(struct snd_pcsp *chip) { - spin_lock_irq(&chip->substream_lock); - if (!chip->playback_substream) - pcspkr_stop_sound(); - spin_unlock_irq(&chip->substream_lock); + pcsp_sync_stop(chip); + pcspkr_stop_sound(); } #ifdef CONFIG_PM diff --git a/sound/drivers/pcsp/pcsp.h b/sound/drivers/pcsp/pcsp.h index 1d661f795e8c..70533a333b5b 100644 --- a/sound/drivers/pcsp/pcsp.h +++ b/sound/drivers/pcsp/pcsp.h @@ -77,6 +77,7 @@ struct snd_pcsp { extern struct snd_pcsp pcsp_chip; extern enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle); +extern void pcsp_sync_stop(struct snd_pcsp *chip); extern int snd_pcsp_new_pcm(struct snd_pcsp *chip); extern int snd_pcsp_new_mixer(struct snd_pcsp *chip); diff --git a/sound/drivers/pcsp/pcsp_lib.c b/sound/drivers/pcsp/pcsp_lib.c index e341f3f83b6a..40f95f549d2b 100644 --- a/sound/drivers/pcsp/pcsp_lib.c +++ b/sound/drivers/pcsp/pcsp_lib.c @@ -8,6 +8,7 @@ #include #include +#include #include #include #include "pcsp.h" @@ -19,6 +20,22 @@ 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); + enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle) { unsigned char timer_cnt, val; @@ -28,41 +45,23 @@ enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle) struct snd_pcm_substream *substream; struct snd_pcm_runtime *runtime; struct snd_pcsp *chip = container_of(handle, struct snd_pcsp, timer); + unsigned long flags; if (chip->thalf) { outb(chip->val61, 0x61); chip->thalf = 0; if (!atomic_read(&chip->timer_active)) - return HRTIMER_NORESTART; + goto stop; hrtimer_forward(&chip->timer, chip->timer.expires, ktime_set(0, chip->ns_rem)); return HRTIMER_RESTART; } - spin_lock_irq(&chip->substream_lock); - /* Takashi Iwai says regarding this extra lock: - - If the irq handler handles some data on the DMA buffer, it should - do snd_pcm_stream_lock(). - That protects basically against all races among PCM callbacks, yes. - However, there are two remaining issues: - 1. The substream pointer you try to lock isn't protected _before_ - this lock yet. - 2. snd_pcm_period_elapsed() itself acquires the lock. - The requirement of another lock is because of 1. When you get - chip->playback_substream, it's not protected. - Keeping this lock while snd_pcm_period_elapsed() assures the substream - is still protected (at least, not released). And the other status is - handled properly inside snd_pcm_stream_lock() in - snd_pcm_period_elapsed(). - - */ - if (!chip->playback_substream) - goto exit_nr_unlock1; - substream = chip->playback_substream; - snd_pcm_stream_lock(substream); if (!atomic_read(&chip->timer_active)) - goto exit_nr_unlock2; + goto stop; + substream = chip->playback_substream; + if (!substream) + goto stop; runtime = substream->runtime; fmt_size = snd_pcm_format_physical_width(runtime->format) >> 3; @@ -87,6 +86,8 @@ enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle) period_bytes = snd_pcm_lib_period_bytes(substream); buffer_bytes = snd_pcm_lib_buffer_bytes(substream); + + spin_lock_irqsave(&chip->substream_lock, flags); chip->playback_ptr += PCSP_INDEX_INC() * fmt_size; periods_elapsed = chip->playback_ptr - chip->period_ptr; if (periods_elapsed < 0) { @@ -102,18 +103,15 @@ enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle) * or ALSA will BUG on us. */ chip->playback_ptr %= buffer_bytes; - snd_pcm_stream_unlock(substream); - if (periods_elapsed) { - snd_pcm_period_elapsed(substream); chip->period_ptr += periods_elapsed * period_bytes; chip->period_ptr %= buffer_bytes; + tasklet_schedule(&pcsp_pcm_tasklet); } - - spin_unlock_irq(&chip->substream_lock); + spin_unlock_irqrestore(&chip->substream_lock, flags); if (!atomic_read(&chip->timer_active)) - return HRTIMER_NORESTART; + goto stop; chip->ns_rem = PCSP_PERIOD_NS(); ns = (chip->thalf ? PCSP_CALC_NS(timer_cnt) : chip->ns_rem); @@ -121,10 +119,7 @@ enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle) hrtimer_forward(&chip->timer, chip->timer.expires, ktime_set(0, ns)); return HRTIMER_RESTART; -exit_nr_unlock2: - snd_pcm_stream_unlock(substream); -exit_nr_unlock1: - spin_unlock_irq(&chip->substream_lock); + stop: return HRTIMER_NORESTART; } @@ -164,26 +159,35 @@ static void pcsp_stop_playing(struct snd_pcsp *chip) spin_unlock(&i8253_lock); } +/* + * Force to stop and sync the stream + */ +void pcsp_sync_stop(struct snd_pcsp *chip) +{ + local_irq_disable(); + 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) { struct snd_pcsp *chip = snd_pcm_substream_chip(substream); #if PCSP_DEBUG printk(KERN_INFO "PCSP: close called\n"); #endif - if (atomic_read(&chip->timer_active)) { - printk(KERN_ERR "PCSP: timer still active\n"); - pcsp_stop_playing(chip); - } - spin_lock_irq(&chip->substream_lock); + pcsp_sync_stop(chip); chip->playback_substream = NULL; - spin_unlock_irq(&chip->substream_lock); return 0; } static int snd_pcsp_playback_hw_params(struct snd_pcm_substream *substream, struct snd_pcm_hw_params *hw_params) { + struct snd_pcsp *chip = snd_pcm_substream_chip(substream); int err; + pcsp_sync_stop(chip); err = snd_pcm_lib_malloc_pages(substream, params_buffer_bytes(hw_params)); if (err < 0) @@ -193,9 +197,11 @@ static int snd_pcsp_playback_hw_params(struct snd_pcm_substream *substream, static int snd_pcsp_playback_hw_free(struct snd_pcm_substream *substream) { + struct snd_pcsp *chip = snd_pcm_substream_chip(substream); #if PCSP_DEBUG printk(KERN_INFO "PCSP: hw_free called\n"); #endif + pcsp_sync_stop(chip); return snd_pcm_lib_free_pages(substream); } @@ -211,6 +217,7 @@ static int snd_pcsp_playback_prepare(struct snd_pcm_substream *substream) snd_pcm_lib_period_bytes(substream), substream->runtime->periods); #endif + pcsp_sync_stop(chip); chip->playback_ptr = 0; chip->period_ptr = 0; return 0; @@ -241,7 +248,11 @@ static snd_pcm_uframes_t snd_pcsp_playback_pointer(struct snd_pcm_substream *substream) { struct snd_pcsp *chip = snd_pcm_substream_chip(substream); - return bytes_to_frames(substream->runtime, chip->playback_ptr); + unsigned int pos; + spin_lock(&chip->substream_lock); + pos = chip->playback_ptr; + spin_unlock(&chip->substream_lock); + return bytes_to_frames(substream->runtime, pos); } static struct snd_pcm_hardware snd_pcsp_playback = { @@ -278,9 +289,7 @@ static int snd_pcsp_playback_open(struct snd_pcm_substream *substream) return -EBUSY; } runtime->hw = snd_pcsp_playback; - spin_lock_irq(&chip->substream_lock); chip->playback_substream = substream; - spin_unlock_irq(&chip->substream_lock); return 0; } -- cgit v1.2.3 From 8a75f4fb28766878893b4335f4b5743ce9b931fe Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Fri, 14 Nov 2008 13:58:43 +0100 Subject: ALSA: pcsp - Use HRTIMER_CB_IRQSAFE_UNLOCKED HRTIMER_CB_IRQSAFE was removed in the upstream. Try to use HRTIMER_CB_IRQSAFE_UNLOCKED instead. Signed-off-by: Takashi Iwai --- sound/drivers/pcsp/pcsp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'sound/drivers/pcsp') diff --git a/sound/drivers/pcsp/pcsp.c b/sound/drivers/pcsp/pcsp.c index 87219bf0a35e..2a02f704f366 100644 --- a/sound/drivers/pcsp/pcsp.c +++ b/sound/drivers/pcsp/pcsp.c @@ -96,7 +96,7 @@ static int __devinit snd_card_pcsp_probe(int devnum, struct device *dev) return -EINVAL; hrtimer_init(&pcsp_chip.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); - pcsp_chip.timer.cb_mode = HRTIMER_CB_IRQSAFE; + pcsp_chip.timer.cb_mode = HRTIMER_CB_IRQSAFE_UNLOCKED; pcsp_chip.timer.function = pcsp_do_timer; card = snd_card_new(index, id, THIS_MODULE, 0); -- cgit v1.2.3