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 <tiwai@suse.de>
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76a4d10e52
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@ -96,7 +96,7 @@ static int __devinit snd_card_pcsp_probe(int devnum, struct device *dev)
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return -EINVAL;
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hrtimer_init(&pcsp_chip.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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pcsp_chip.timer.cb_mode = HRTIMER_CB_SOFTIRQ;
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pcsp_chip.timer.cb_mode = HRTIMER_CB_IRQSAFE;
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pcsp_chip.timer.function = pcsp_do_timer;
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card = snd_card_new(index, id, THIS_MODULE, 0);
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@ -188,10 +188,8 @@ static int __devexit pcsp_remove(struct platform_device *dev)
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static void pcsp_stop_beep(struct snd_pcsp *chip)
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{
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spin_lock_irq(&chip->substream_lock);
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if (!chip->playback_substream)
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pcspkr_stop_sound();
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spin_unlock_irq(&chip->substream_lock);
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pcsp_sync_stop(chip);
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pcspkr_stop_sound();
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}
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#ifdef CONFIG_PM
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@ -77,6 +77,7 @@ struct snd_pcsp {
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extern struct snd_pcsp pcsp_chip;
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extern enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle);
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extern void pcsp_sync_stop(struct snd_pcsp *chip);
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extern int snd_pcsp_new_pcm(struct snd_pcsp *chip);
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extern int snd_pcsp_new_mixer(struct snd_pcsp *chip);
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@ -8,6 +8,7 @@
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/interrupt.h>
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#include <sound/pcm.h>
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#include <asm/io.h>
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#include "pcsp.h"
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@ -19,6 +20,22 @@ MODULE_PARM_DESC(nforce_wa, "Apply NForce chipset workaround "
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#define DMIX_WANTS_S16 1
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/*
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* Call snd_pcm_period_elapsed in a tasklet
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* This avoids spinlock messes and long-running irq contexts
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*/
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static void pcsp_call_pcm_elapsed(unsigned long priv)
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{
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if (atomic_read(&pcsp_chip.timer_active)) {
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struct snd_pcm_substream *substream;
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substream = pcsp_chip.playback_substream;
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if (substream)
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snd_pcm_period_elapsed(substream);
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}
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}
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static DECLARE_TASKLET(pcsp_pcm_tasklet, pcsp_call_pcm_elapsed, 0);
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enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle)
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{
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unsigned char timer_cnt, val;
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@ -28,41 +45,23 @@ enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle)
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struct snd_pcm_substream *substream;
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struct snd_pcm_runtime *runtime;
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struct snd_pcsp *chip = container_of(handle, struct snd_pcsp, timer);
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unsigned long flags;
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if (chip->thalf) {
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outb(chip->val61, 0x61);
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chip->thalf = 0;
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if (!atomic_read(&chip->timer_active))
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return HRTIMER_NORESTART;
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goto stop;
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hrtimer_forward(&chip->timer, chip->timer.expires,
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ktime_set(0, chip->ns_rem));
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return HRTIMER_RESTART;
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}
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spin_lock_irq(&chip->substream_lock);
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/* Takashi Iwai says regarding this extra lock:
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If the irq handler handles some data on the DMA buffer, it should
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do snd_pcm_stream_lock().
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That protects basically against all races among PCM callbacks, yes.
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However, there are two remaining issues:
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1. The substream pointer you try to lock isn't protected _before_
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this lock yet.
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2. snd_pcm_period_elapsed() itself acquires the lock.
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The requirement of another lock is because of 1. When you get
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chip->playback_substream, it's not protected.
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Keeping this lock while snd_pcm_period_elapsed() assures the substream
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is still protected (at least, not released). And the other status is
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handled properly inside snd_pcm_stream_lock() in
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snd_pcm_period_elapsed().
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*/
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if (!chip->playback_substream)
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goto exit_nr_unlock1;
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substream = chip->playback_substream;
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snd_pcm_stream_lock(substream);
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if (!atomic_read(&chip->timer_active))
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goto exit_nr_unlock2;
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goto stop;
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substream = chip->playback_substream;
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if (!substream)
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goto stop;
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runtime = substream->runtime;
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fmt_size = snd_pcm_format_physical_width(runtime->format) >> 3;
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@ -87,6 +86,8 @@ enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle)
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period_bytes = snd_pcm_lib_period_bytes(substream);
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buffer_bytes = snd_pcm_lib_buffer_bytes(substream);
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spin_lock_irqsave(&chip->substream_lock, flags);
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chip->playback_ptr += PCSP_INDEX_INC() * fmt_size;
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periods_elapsed = chip->playback_ptr - chip->period_ptr;
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if (periods_elapsed < 0) {
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@ -102,18 +103,15 @@ enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle)
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* or ALSA will BUG on us. */
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chip->playback_ptr %= buffer_bytes;
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snd_pcm_stream_unlock(substream);
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if (periods_elapsed) {
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snd_pcm_period_elapsed(substream);
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chip->period_ptr += periods_elapsed * period_bytes;
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chip->period_ptr %= buffer_bytes;
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tasklet_schedule(&pcsp_pcm_tasklet);
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}
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spin_unlock_irq(&chip->substream_lock);
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spin_unlock_irqrestore(&chip->substream_lock, flags);
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if (!atomic_read(&chip->timer_active))
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return HRTIMER_NORESTART;
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goto stop;
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chip->ns_rem = PCSP_PERIOD_NS();
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ns = (chip->thalf ? PCSP_CALC_NS(timer_cnt) : chip->ns_rem);
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@ -121,10 +119,7 @@ enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle)
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hrtimer_forward(&chip->timer, chip->timer.expires, ktime_set(0, ns));
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return HRTIMER_RESTART;
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exit_nr_unlock2:
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snd_pcm_stream_unlock(substream);
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exit_nr_unlock1:
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spin_unlock_irq(&chip->substream_lock);
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stop:
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return HRTIMER_NORESTART;
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}
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@ -164,26 +159,35 @@ static void pcsp_stop_playing(struct snd_pcsp *chip)
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spin_unlock(&i8253_lock);
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}
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/*
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* Force to stop and sync the stream
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*/
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void pcsp_sync_stop(struct snd_pcsp *chip)
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{
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local_irq_disable();
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pcsp_stop_playing(chip);
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local_irq_enable();
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hrtimer_cancel(&chip->timer);
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tasklet_kill(&pcsp_pcm_tasklet);
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}
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static int snd_pcsp_playback_close(struct snd_pcm_substream *substream)
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{
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struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
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#if PCSP_DEBUG
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printk(KERN_INFO "PCSP: close called\n");
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#endif
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if (atomic_read(&chip->timer_active)) {
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printk(KERN_ERR "PCSP: timer still active\n");
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pcsp_stop_playing(chip);
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}
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spin_lock_irq(&chip->substream_lock);
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pcsp_sync_stop(chip);
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chip->playback_substream = NULL;
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spin_unlock_irq(&chip->substream_lock);
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return 0;
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}
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static int snd_pcsp_playback_hw_params(struct snd_pcm_substream *substream,
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struct snd_pcm_hw_params *hw_params)
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{
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struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
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int err;
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pcsp_sync_stop(chip);
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err = snd_pcm_lib_malloc_pages(substream,
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params_buffer_bytes(hw_params));
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if (err < 0)
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@ -193,9 +197,11 @@ static int snd_pcsp_playback_hw_params(struct snd_pcm_substream *substream,
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static int snd_pcsp_playback_hw_free(struct snd_pcm_substream *substream)
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{
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struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
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#if PCSP_DEBUG
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printk(KERN_INFO "PCSP: hw_free called\n");
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#endif
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pcsp_sync_stop(chip);
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return snd_pcm_lib_free_pages(substream);
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}
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@ -211,6 +217,7 @@ static int snd_pcsp_playback_prepare(struct snd_pcm_substream *substream)
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snd_pcm_lib_period_bytes(substream),
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substream->runtime->periods);
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#endif
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pcsp_sync_stop(chip);
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chip->playback_ptr = 0;
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chip->period_ptr = 0;
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return 0;
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@ -241,7 +248,11 @@ static snd_pcm_uframes_t snd_pcsp_playback_pointer(struct snd_pcm_substream
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*substream)
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{
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struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
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return bytes_to_frames(substream->runtime, chip->playback_ptr);
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unsigned int pos;
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spin_lock(&chip->substream_lock);
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pos = chip->playback_ptr;
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spin_unlock(&chip->substream_lock);
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return bytes_to_frames(substream->runtime, pos);
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}
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static struct snd_pcm_hardware snd_pcsp_playback = {
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return -EBUSY;
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}
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runtime->hw = snd_pcsp_playback;
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spin_lock_irq(&chip->substream_lock);
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chip->playback_substream = substream;
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spin_unlock_irq(&chip->substream_lock);
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return 0;
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}
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