[PATCH 1/2] clocksource/drivers/timer-ti-dm: Unregister CPU PM notifier outside of the timer lock

[Bradley Morgan]

omap_dm_timer_remove() calls cpu_pm_unregister_notifier() with
dm_timer_lock held and interrupts disabled. Nothing sleeps in there
today, but it pins the helper into a context where it can never be
allowed to sleep, which is in the way of restoring the RCU grace
period on the cpu_pm notifier chain.

Do the list lookup under the lock and move the unregister after the
unlock. Nothing can race it at that point: remove() owns the device,
and once the timer is off the list nobody can reach it anymore.

Signed-off-by: Bradley Morgan <include@xxxxxxxxx>
---
 drivers/clocksource/timer-ti-dm.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/clocksource/timer-ti-dm.c b/drivers/clocksource/timer-ti-dm.c
index bd06afb7d522..032e102bdd0a 100644
--- a/drivers/clocksource/timer-ti-dm.c
+++ b/drivers/clocksource/timer-ti-dm.c
@@ -1530,7 +1530,7 @@ static int omap_dm_timer_probe(struct platform_device *pdev)
  */
 static void omap_dm_timer_remove(struct platform_device *pdev)
 {
-	struct dmtimer *timer;
+	struct dmtimer *timer, *found = NULL;
 	unsigned long flags;
 	int ret = -EINVAL;
 
@@ -1538,14 +1538,17 @@ static void omap_dm_timer_remove(struct platform_device *pdev)
 	list_for_each_entry(timer, &omap_timer_list, node)
 		if (!strcmp(dev_name(&timer->pdev->dev),
 			    dev_name(&pdev->dev))) {
-			if (!(timer->capability & OMAP_TIMER_ALWON))
-				cpu_pm_unregister_notifier(&timer->nb);
 			list_del(&timer->node);
+			found = timer;
 			ret = 0;
 			break;
 		}
 	spin_unlock_irqrestore(&dm_timer_lock, flags);
 
+	/* Unregister outside the lock: cpu_pm_unregister_notifier() may sleep. */
+	if (found && !(found->capability & OMAP_TIMER_ALWON))
+		cpu_pm_unregister_notifier(&found->nb);
+
 	pm_runtime_disable(&pdev->dev);
 
 	if (ret)
-- 
2.47.3