[PATCH v2] PM / Sleep: Use workqueue for user space wakeup sources garbage collector

[SungEun Kim]

From: "SungEun Kim" <cleaneye.kim@xxxxxxx>

The synchronous synchronize_rcu in wakeup_source_remove makes user process
which writes to /sys/kernel/wake_unlock blocked sometimes.

For example, when android eventhub tries to release wakelock,
this blocking process can occur, and eventhub can't get input event
for a while.

Using workqueue instead of direct function call at pm_wake_unlock
can prevent this unnecessary delay of an user space process.

Signed-off-by: SungEun Kim <cleaneye.kim@xxxxxxx>
---
 kernel/power/wakelock.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/power/wakelock.c b/kernel/power/wakelock.c
index 019069c..5df6aa2 100644
--- a/kernel/power/wakelock.c
+++ b/kernel/power/wakelock.c
@@ -17,6 +17,7 @@
 #include <linux/list.h>
 #include <linux/rbtree.h>
 #include <linux/slab.h>
+#include <linux/workqueue.h>
 
 #include "power.h"
 
@@ -83,7 +84,9 @@ static inline void decrement_wakelocks_number(void) {}
 #define WL_GC_COUNT_MAX	100
 #define WL_GC_TIME_SEC	300
 
+static void __wakelocks_gc(struct work_struct *work);
 static LIST_HEAD(wakelocks_lru_list);
+static DECLARE_WORK(wakelock_work, __wakelocks_gc);
 static unsigned int wakelocks_gc_count;
 
 static inline void wakelocks_lru_add(struct wakelock *wl)
@@ -96,7 +99,7 @@ static inline void wakelocks_lru_most_recent(struct wakelock *wl)
 	list_move(&wl->lru, &wakelocks_lru_list);
 }
 
-static void wakelocks_gc(void)
+static void __wakelocks_gc(struct work_struct *work)
 {
 	struct wakelock *wl, *aux;
 	ktime_t now;
@@ -105,6 +108,7 @@ static void wakelocks_gc(void)
 		return;
 
 	now = ktime_get();
+	mutex_lock(&wakelocks_lock);
 	list_for_each_entry_safe_reverse(wl, aux, &wakelocks_lru_list, lru) {
 		u64 idle_time_ns;
 		bool active;
@@ -126,8 +130,14 @@ static void wakelocks_gc(void)
 			decrement_wakelocks_number();
 		}
 	}
+	mutex_unlock(&wakelocks_lock);
 	wakelocks_gc_count = 0;
 }
+
+static void wakelocks_gc(void)
+{
+	schedule_work(&wakelock_work);
+}
 #else /* !CONFIG_PM_WAKELOCKS_GC */
 static inline void wakelocks_lru_add(struct wakelock *wl) {}
 static inline void wakelocks_lru_most_recent(struct wakelock *wl) {}
-- 
1.7.9.5

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