[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>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 9d260e838cff..ca8ef11feb65 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -389,7 +389,7 @@ static struct task_struct * futex_find_get_task(pid_t pid)
 {
         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 @@ static struct task_struct * futex_find_get_task(pid_t pid)
         }
         get_task_struct(p);
 out_unlock:
-        read_unlock(&tasklist_lock);
+        rcu_read_unlock();
 
         return p;
 }