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fcfdebe707
The timer stop callback can be called from snd_timer_interrupt(), which is called from the hrtimer callback. Since hrtimer_cancel() waits for the callback completion, this eventually results in a lock-up. This patch fixes the problem by just toggling a flag at stop callback and call hrtimer_cancel() later. Reported-and-tested-by: Wojtek Zabolotny <W.Zabolotny@elka.pw.edu.pl> Cc: <stable@kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
165 lines
4 KiB
C
165 lines
4 KiB
C
/*
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* ALSA timer back-end using hrtimer
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* Copyright (C) 2008 Takashi Iwai
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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*/
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/hrtimer.h>
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#include <sound/core.h>
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#include <sound/timer.h>
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MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
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MODULE_DESCRIPTION("ALSA hrtimer backend");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER));
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#define NANO_SEC 1000000000UL /* 10^9 in sec */
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static unsigned int resolution;
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struct snd_hrtimer {
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struct snd_timer *timer;
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struct hrtimer hrt;
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atomic_t running;
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};
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static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)
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{
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struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt);
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struct snd_timer *t = stime->timer;
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if (!atomic_read(&stime->running))
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return HRTIMER_NORESTART;
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hrtimer_forward_now(hrt, ns_to_ktime(t->sticks * resolution));
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snd_timer_interrupt(stime->timer, t->sticks);
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if (!atomic_read(&stime->running))
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return HRTIMER_NORESTART;
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return HRTIMER_RESTART;
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}
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static int snd_hrtimer_open(struct snd_timer *t)
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{
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struct snd_hrtimer *stime;
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stime = kmalloc(sizeof(*stime), GFP_KERNEL);
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if (!stime)
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return -ENOMEM;
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hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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stime->timer = t;
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stime->hrt.function = snd_hrtimer_callback;
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atomic_set(&stime->running, 0);
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t->private_data = stime;
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return 0;
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}
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static int snd_hrtimer_close(struct snd_timer *t)
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{
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struct snd_hrtimer *stime = t->private_data;
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if (stime) {
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hrtimer_cancel(&stime->hrt);
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kfree(stime);
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t->private_data = NULL;
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}
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return 0;
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}
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static int snd_hrtimer_start(struct snd_timer *t)
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{
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struct snd_hrtimer *stime = t->private_data;
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atomic_set(&stime->running, 0);
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hrtimer_cancel(&stime->hrt);
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hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution),
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HRTIMER_MODE_REL);
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atomic_set(&stime->running, 1);
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return 0;
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}
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static int snd_hrtimer_stop(struct snd_timer *t)
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{
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struct snd_hrtimer *stime = t->private_data;
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atomic_set(&stime->running, 0);
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return 0;
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}
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static struct snd_timer_hardware hrtimer_hw = {
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.flags = SNDRV_TIMER_HW_AUTO,
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.open = snd_hrtimer_open,
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.close = snd_hrtimer_close,
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.start = snd_hrtimer_start,
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.stop = snd_hrtimer_stop,
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};
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/*
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* entry functions
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*/
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static struct snd_timer *mytimer;
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static int __init snd_hrtimer_init(void)
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{
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struct snd_timer *timer;
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struct timespec tp;
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int err;
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hrtimer_get_res(CLOCK_MONOTONIC, &tp);
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if (tp.tv_sec > 0 || !tp.tv_nsec) {
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snd_printk(KERN_ERR
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"snd-hrtimer: Invalid resolution %u.%09u",
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(unsigned)tp.tv_sec, (unsigned)tp.tv_nsec);
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return -EINVAL;
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}
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resolution = tp.tv_nsec;
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/* Create a new timer and set up the fields */
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err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER,
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&timer);
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if (err < 0)
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return err;
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timer->module = THIS_MODULE;
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strcpy(timer->name, "HR timer");
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timer->hw = hrtimer_hw;
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timer->hw.resolution = resolution;
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timer->hw.ticks = NANO_SEC / resolution;
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err = snd_timer_global_register(timer);
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if (err < 0) {
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snd_timer_global_free(timer);
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return err;
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}
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mytimer = timer; /* remember this */
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return 0;
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}
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static void __exit snd_hrtimer_exit(void)
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{
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if (mytimer) {
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snd_timer_global_free(mytimer);
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mytimer = NULL;
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}
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}
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module_init(snd_hrtimer_init);
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module_exit(snd_hrtimer_exit);
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