[PATCH] futex_find_get_task(): don't take tasklist_lock
It is ok to do find_task_by_pid() + get_task_struct() under
rcu_read_lock(), we cand drop tasklist_lock.
Note that testing of ->exit_state is racy with or without tasklist anyway.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/futex.c b/kernel/futex.c
index 9d260e83..ca8ef11 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -389,7 +389,7 @@
{
struct task_struct *p;
- read_lock(&tasklist_lock);
+ rcu_read_lock();
p = find_task_by_pid(pid);
if (!p)
goto out_unlock;
@@ -403,7 +403,7 @@
}
get_task_struct(p);
out_unlock:
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
return p;
}
