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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: Brian Norris <briannorris@chromium.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Ulf Hansson 2017-02-08 13:39:00 +01:00 committed by Rafael J. Wysocki
parent f3c826ac26
commit 0883ac038b
1 changed files with 39 additions and 29 deletions
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68
drivers/base/power/domain.c
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@ -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--;
}
}