+ proc_oom_score-remove-tasklist_lock-and-pid_alive.patch added to -mm tree

+ proc_oom_score-remove-tasklist_lock-and-pid_alive.patch added to -mm tree

[akpm]

The patch titled
     Subject: proc_oom_score: remove tasklist_lock and pid_alive()
has been added to the -mm tree.  Its filename is
     proc_oom_score-remove-tasklist_lock-and-pid_alive.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/proc_oom_score-remove-tasklist_lock-and-pid_alive.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/proc_oom_score-remove-tasklist_lock-and-pid_alive.patch

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------------------------------------------------------
From: Oleg Nesterov <oleg@redhat.com>
Subject: 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 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>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/proc/base.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff -puN fs/proc/base.c~proc_oom_score-remove-tasklist_lock-and-pid_alive fs/proc/base.c
--- a/fs/proc/base.c~proc_oom_score-remove-tasklist_lock-and-pid_alive
+++ a/fs/proc/base.c
@@ -579,11 +579,8 @@ static int proc_oom_score(struct seq_fil
 	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;
_

Patches currently in -mm which might be from oleg@redhat.com are

proc_oom_score-remove-tasklist_lock-and-pid_alive.patch