Commit 0883ac03 authored by Ulf Hansson's avatar Ulf Hansson Committed by Rafael J. Wysocki
Browse files

PM / Domains: Fix asynchronous execution of *noirq() callbacks 



As the PM core may invoke the *noirq() callbacks asynchronously, the
current lock-less approach in genpd doesn't work. The consequence is that
we may find concurrent operations racing to power on/off the PM domain.

As of now, no immediate errors has been reported, but it's probably only a
matter time. Therefor let's fix the problem now before this becomes a real
issue, by deploying the locking scheme to the relevant functions.

Reported-by: default avatarBrian Norris <briannorris@chromium.org>
Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
Tested-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent f3c826ac

drivers/base/power/domain.c

+39 −29
Original line number Diff line number Diff line
@@ -729,16 +729,18 @@ static bool genpd_dev_active_wakeup(struct generic_pm_domain *genpd, 
/**

 * genpd_sync_power_off - Synchronously power off a PM domain and its masters.

 * @genpd: PM domain to power off, if possible.

 * @use_lock: use the lock.

 * @depth: nesting count for lockdep.

 *

 * Check if the given PM domain can be powered off (during system suspend or

 * hibernation) and do that if so.  Also, in that case propagate to its masters.

 *

 * This function is only called in "noirq" and "syscore" stages of system power

 * transitions, so it need not acquire locks (all of the "noirq" callbacks are

 * executed sequentially, so it is guaranteed that it will never run twice in

 * parallel).

 * transitions. The "noirq" callbacks may be executed asynchronously, thus in

 * these cases the lock must be held.

 */

static void genpd_sync_power_off(struct generic_pm_domain *genpd)

static void genpd_sync_power_off(struct generic_pm_domain *genpd, bool use_lock,

				 unsigned int depth)

{

	struct gpd_link *link;
@@ -757,20 +759,29 @@ static void genpd_sync_power_off(struct generic_pm_domain *genpd) 


	list_for_each_entry(link, &genpd->slave_links, slave_node) {

		genpd_sd_counter_dec(link->master);

		genpd_sync_power_off(link->master);



		if (use_lock)

			genpd_lock_nested(link->master, depth + 1);



		genpd_sync_power_off(link->master, use_lock, depth + 1);



		if (use_lock)

			genpd_unlock(link->master);

	}

}



/**

 * genpd_sync_power_on - Synchronously power on a PM domain and its masters.

 * @genpd: PM domain to power on.

 * @use_lock: use the lock.

 * @depth: nesting count for lockdep.

 *

 * This function is only called in "noirq" and "syscore" stages of system power

 * transitions, so it need not acquire locks (all of the "noirq" callbacks are

 * executed sequentially, so it is guaranteed that it will never run twice in

 * parallel).

 * transitions. The "noirq" callbacks may be executed asynchronously, thus in

 * these cases the lock must be held.

 */

static void genpd_sync_power_on(struct generic_pm_domain *genpd)

static void genpd_sync_power_on(struct generic_pm_domain *genpd, bool use_lock,

				unsigned int depth)

{

	struct gpd_link *link;
@@ -778,8 +789,15 @@ static void genpd_sync_power_on(struct generic_pm_domain *genpd) 
		return;



	list_for_each_entry(link, &genpd->slave_links, slave_node) {

		genpd_sync_power_on(link->master);

		genpd_sd_counter_inc(link->master);



		if (use_lock)

			genpd_lock_nested(link->master, depth + 1);



		genpd_sync_power_on(link->master, use_lock, depth + 1);



		if (use_lock)

			genpd_unlock(link->master);

	}



	_genpd_power_on(genpd, false);
@@ -888,13 +906,10 @@ static int pm_genpd_suspend_noirq(struct device *dev) 
			return ret;

	}



	/*

	 * Since all of the "noirq" callbacks are executed sequentially, it is

	 * guaranteed that this function will never run twice in parallel for

	 * the same PM domain, so it is not necessary to use locking here.

	 */

	genpd_lock(genpd);

	genpd->suspended_count++;

	genpd_sync_power_off(genpd);

	genpd_sync_power_off(genpd, true, 0);

	genpd_unlock(genpd);



	return 0;

}
@@ -919,13 +934,10 @@ static int pm_genpd_resume_noirq(struct device *dev) 
	if (dev->power.wakeup_path && genpd_dev_active_wakeup(genpd, dev))

		return 0;



	/*

	 * Since all of the "noirq" callbacks are executed sequentially, it is

	 * guaranteed that this function will never run twice in parallel for

	 * the same PM domain, so it is not necessary to use locking here.

	 */

	genpd_sync_power_on(genpd);

	genpd_lock(genpd);

	genpd_sync_power_on(genpd, true, 0);

	genpd->suspended_count--;

	genpd_unlock(genpd);



	if (genpd->dev_ops.stop && genpd->dev_ops.start)

		ret = pm_runtime_force_resume(dev);
@@ -1002,13 +1014,10 @@ static int pm_genpd_restore_noirq(struct device *dev) 
		return -EINVAL;



	/*

	 * Since all of the "noirq" callbacks are executed sequentially, it is

	 * guaranteed that this function will never run twice in parallel for

	 * the same PM domain, so it is not necessary to use locking here.

	 *

	 * At this point suspended_count == 0 means we are being run for the

	 * first time for the given domain in the present cycle.

	 */

	genpd_lock(genpd);

	if (genpd->suspended_count++ == 0)

		/*

		 * The boot kernel might put the domain into arbitrary state,
@@ -1017,7 +1026,8 @@ static int pm_genpd_restore_noirq(struct device *dev) 
		 */

		genpd->status = GPD_STATE_POWER_OFF;



	genpd_sync_power_on(genpd);

	genpd_sync_power_on(genpd, true, 0);

	genpd_unlock(genpd);



	if (genpd->dev_ops.stop && genpd->dev_ops.start)

		ret = pm_runtime_force_resume(dev);
@@ -1072,9 +1082,9 @@ static void genpd_syscore_switch(struct device *dev, bool suspend) 


	if (suspend) {

		genpd->suspended_count++;

		genpd_sync_power_off(genpd);

		genpd_sync_power_off(genpd, false, 0);

	} else {

		genpd_sync_power_on(genpd);

		genpd_sync_power_on(genpd, false, 0);

		genpd->suspended_count--;

	}

}

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