proc_oom_score: remove tasklist_lock and pid_alive()

PATCH Applied Oleg Nesterov 3 participants 3 messages Jun 8, 2016 – Jun 9, 2016 Proc filesystem

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Oleg Nesterov

author

2016-06-08 21:19 UTC #0 lore raw

PATCH 1/1 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 the commit b95c35e76b29b for details.

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

Signed-off-by Oleg Nesterov <[email protected]>

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

fs/proc/base.c +2 -5

index a11eb71..93e7754 100644
@@ -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;

Signature · 1 line

2.5.0

David Rientjes

Acked-by on v1 1/1

2016-06-08 22:48 UTC #1 lore raw

Quoted 6 lines · Oleg Nesterov

This was needed before to ensure that ->signal != 0 and do_each_thread() is safe, see the commit b95c35e76b29b for details.
Today tsk->signal can't go away and for_each_thread(tsk) is always safe.
Signed-off-by Oleg Nesterov <[email protected]>

Acked-by David Rientjes <[email protected]>

Michal Hocko

Acked-by on v1 1/1

2016-06-09 06:45 UTC #2 lore raw

In reply to Oleg Nesterov

Quoted 6 lines · Oleg Nesterov

This was needed before to ensure that ->signal != 0 and do_each_thread() is safe, see the commit b95c35e76b29b for details.
Today tsk->signal can't go away and for_each_thread(tsk) is always safe.
Signed-off-by Oleg Nesterov <[email protected]>

Acked-by Michal Hocko <[email protected]>

Quoted 25 lines

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

fs/proc/base.c +2 -5

index a11eb71..93e7754 100644
@@ -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;

Signature · 1 line

2.5.0

Signature · 2 lines

Michal Hocko
SUSE Labs