proc_oom_score: remove tasklist_lock and pid_alive()

This was needed before to ensure that ->signal != 0 and do_each_thread()
is safe, see commit b95c35e76b29b ("oom: fix the unsafe usage of
badness() in proc_oom_score()") for details.

Today tsk->signal can't go away and for_each_thread(tsk) is always safe.

Link: http://lkml.kernel.org/r/20160608211921.GA15508@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 31370da..54e2702 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -579,11 +579,8 @@ static int proc_oom_score(struct seq_file *m, struct pid_namespace *ns,
        unsigned long totalpages = totalram_pages + total_swap_pages;
        unsigned long points = 0;
 
-       read_lock(&tasklist_lock);
-       if (pid_alive(task))
-               points = oom_badness(task, NULL, NULL, totalpages) *
-                                               1000 / totalpages;
-       read_unlock(&tasklist_lock);
+       points = oom_badness(task, NULL, NULL, totalpages) *
+                                       1000 / totalpages;
        seq_printf(m, "%lu\n", points);
 
        return 0;