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Commit e9728f0d authored by Dmitry Torokhov's avatar Dmitry Torokhov
Browse files

Input: pwm-beeper - fix race when suspending 



Usually userspace sends SND_BELL and SND_TONE events, and by the time
pwm_beeper_suspend() runs userpsace is already frozen, but theoretically
in-kernel users may send these events too, and that may cause
pwm_beeper_event() scheduling another work after we canceled it.

Let's introduce a "suspended" flag and check it in pwm_beeper_event() to
avoid this race.

Reviewed-by: default avatarThierry Reding <thierry.reding@gmail.com>
Tested-by: default avatarDavid Lechner <david@lechnology.com>
Signed-off-by: default avatarDmitry Torokhov <dmitry.torokhov@gmail.com>
parent 48a55d7d

drivers/input/misc/pwm-beeper.c

+18 −3
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ struct pwm_beeper { 
	struct pwm_device *pwm;

	struct work_struct work;

	unsigned long period;

	bool suspended;

};



#define HZ_TO_NANOSECONDS(x) (1000000000UL/(x))
@@ -73,6 +74,7 @@ static int pwm_beeper_event(struct input_dev *input, 
	else

		beeper->period = HZ_TO_NANOSECONDS(value);



	if (!beeper->suspended)

		schedule_work(&beeper->work);



	return 0;
@@ -154,6 +156,15 @@ static int __maybe_unused pwm_beeper_suspend(struct device *dev) 
{

	struct pwm_beeper *beeper = dev_get_drvdata(dev);



	/*

	 * Spinlock is taken here is not to protect write to

	 * beeper->suspended, but to ensure that pwm_beeper_event

	 * does not re-submit work once flag is set.

	 */

	spin_lock_irq(&beeper->input->event_lock);

	beeper->suspended = true;

	spin_unlock_irq(&beeper->input->event_lock);



	pwm_beeper_stop(beeper);



	return 0;
@@ -163,8 +174,12 @@ static int __maybe_unused pwm_beeper_resume(struct device *dev) 
{

	struct pwm_beeper *beeper = dev_get_drvdata(dev);



	if (beeper->period)

		__pwm_beeper_set(beeper);

	spin_lock_irq(&beeper->input->event_lock);

	beeper->suspended = false;

	spin_unlock_irq(&beeper->input->event_lock);



	/* Let worker figure out if we should resume beeping */

	schedule_work(&beeper->work);



	return 0;

}