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 with rcu_read_{,un}lock().
From now on using force_sig() is not safe, as it can race with an
already exiting task, so we use send_sig() now. As a downside, it won't kill PID namespace init processes, but that's not what we want anyway.
Suggested-by: Oleg Nesterov oleg@redhat.com Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org --- drivers/staging/android/lowmemorykiller.c | 7 ++++--- 1 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c index 2d8d2b7..63da844 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; @@ -180,12 +181,12 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc) lowmem_deathpending = selected; task_handoff_register(&task_nb); #endif - force_sig(SIGKILL, selected); + send_sig(SIGKILL, selected, 0); rem -= selected_tasksize; } 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; }