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authorTirupathi Reddy <tirupath@codeaurora.org>2017-07-12 14:38:13 +0300
committerMark Brown <broonie@kernel.org>2017-07-20 15:22:29 +0300
commitc9ccaa0cac3fc8e7d17a668aabfdf632c7c0517a (patch)
tree18bec2aa296cb39252cfa511a7f0932ce19ae5b0 /drivers/regulator
parent5771a8c08880cdca3bfb4a3fc6d309d6bba20877 (diff)
downloadlinux-c9ccaa0cac3fc8e7d17a668aabfdf632c7c0517a.tar.xz
regulator: core: fix a possible race in disable_work handling
A race condition between queueing and processing the disable_work instances results in having a work instance in the queue and the deferred_disables variable of regulator device structure having a value '0'. If no new regulator_disable_deferred() call later from clients, the deferred_disables variable value remains '0' and hits BUG() in regulator_disable_work() when the queued instance scheduled for processing the work. The race occurs as below: Core-0 Core-1 ..... /* deferred_disables = 2 */ ..... ..... /* disable_work is queued */ ..... ..... ..... regulator_disable_deferred: regulator_disable_work: mutex_lock(&rdev->mutex); ..... rdev->deferred_disables++; ..... mutex_unlock(&rdev->mutex); ..... queue_delayed_work(...) mutex_lock(&rdev->mutex); ..... count =rdev->deferred_disables; ..... rdev->deferred_disables = 0; ..... ..... ..... mutex_unlock(&rdev->mutex); ..... ..... ..... return; ..... ..... /* No new regulator_disable_deferred() calls from clients */ /* The newly queued instance is scheduled for processing */ ..... ..... regulator_disable_work: ..... mutex_lock(&rdev->mutex); BUG_ON(!rdev->deferred_disables); /* deferred_disables = 0 */ The race is fixed by removing the work instance that is queued while processing the previous queued instance. Cancel the newly queued instance from disable_work() handler just after reset the deferred_disables variable to value '0'. Also move the work queueing step before mutex_unlock in regulator_disable_deferred(). Also use mod_delayed_work() in the pace of queue_delayed_work() as queue_delayed_work() always uses the delay requested in the first call when multiple consumers call regulator_disable_deferred() close in time and does not guarantee the semantics of regulator_disable_deferred(). Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org> Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/regulator')
-rw-r--r--drivers/regulator/core.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index e567fa54980b..9f4d484eb25d 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -2396,6 +2396,14 @@ static void regulator_disable_work(struct work_struct *work)
count = rdev->deferred_disables;
rdev->deferred_disables = 0;
+ /*
+ * Workqueue functions queue the new work instance while the previous
+ * work instance is being processed. Cancel the queued work instance
+ * as the work instance under processing does the job of the queued
+ * work instance.
+ */
+ cancel_delayed_work(&rdev->disable_work);
+
for (i = 0; i < count; i++) {
ret = _regulator_disable(rdev);
if (ret != 0)
@@ -2439,10 +2447,10 @@ int regulator_disable_deferred(struct regulator *regulator, int ms)
mutex_lock(&rdev->mutex);
rdev->deferred_disables++;
+ mod_delayed_work(system_power_efficient_wq, &rdev->disable_work,
+ msecs_to_jiffies(ms));
mutex_unlock(&rdev->mutex);
- queue_delayed_work(system_power_efficient_wq, &rdev->disable_work,
- msecs_to_jiffies(ms));
return 0;
}
EXPORT_SYMBOL_GPL(regulator_disable_deferred);