staging: android/lowmemorykiller: Better mm handling
LMK should not directly check for task->mm. The reason is that the
process' threads may exit or detach its mm via use_mm(), but other
threads may still have a valid mm. To catch this we use
find_lock_task_mm(), which walks up all threads and returns an
appropriate task (with lock held).
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
index 63da844..0755e2f 100644
--- a/drivers/staging/android/lowmemorykiller.c
+++ b/drivers/staging/android/lowmemorykiller.c
@@ -82,7 +82,7 @@
static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
{
- struct task_struct *p;
+ struct task_struct *tsk;
struct task_struct *selected = NULL;
int rem = 0;
int tasksize;
@@ -134,15 +134,17 @@
selected_oom_adj = min_adj;
rcu_read_lock();
- for_each_process(p) {
- struct mm_struct *mm;
+ for_each_process(tsk) {
+ struct task_struct *p;
struct signal_struct *sig;
int oom_adj;
- task_lock(p);
- mm = p->mm;
+ p = find_lock_task_mm(tsk);
+ if (!p)
+ continue;
+
sig = p->signal;
- if (!mm || !sig) {
+ if (!sig) {
task_unlock(p);
continue;
}
@@ -151,7 +153,7 @@
task_unlock(p);
continue;
}
- tasksize = get_mm_rss(mm);
+ tasksize = get_mm_rss(p->mm);
task_unlock(p);
if (tasksize <= 0)
continue;