[PATCH] staging: android/lowmemorykiller: Don't grab tasklist_lock

Anton Vorontsov anton.vorontsov at linaro.org
Wed Feb 1 04:33:30 UTC 2012

Grabbing tasklist_lock has its disadvantages, i.e. it blocks
process creation and destruction. If there are lots of processes,
blocking doesn't sound as a great idea.

For LMK, it is sufficient to surround tasks list traverse loop
with rcu_read_{,un}lock() pair.

Suggested-by: Oleg Nesterov <oleg at redhat.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov at linaro.org>

Also thanks to Eric and Paul for the ideas.

 drivers/staging/android/lowmemorykiller.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
index 2d8d2b7..b3ade2f 100644
--- a/drivers/staging/android/lowmemorykiller.c
+++ b/drivers/staging/android/lowmemorykiller.c
@@ -34,6 +34,7 @@
 #include <linux/mm.h>
 #include <linux/oom.h>
 #include <linux/sched.h>
+#include <linux/rcupdate.h>
 #include <linux/profile.h>
 #include <linux/notifier.h>
@@ -132,7 +133,7 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
 	selected_oom_adj = min_adj;
-	read_lock(&tasklist_lock);
+	rcu_read_lock();
 	for_each_process(p) {
 		struct mm_struct *mm;
 		struct signal_struct *sig;
@@ -185,7 +186,7 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
 	lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n",
 		     sc->nr_to_scan, sc->gfp_mask, rem);
-	read_unlock(&tasklist_lock);
+	rcu_read_unlock();
 	return rem;

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