[PATCH 2/3] futex_find_get_task: don't take tasklist_lock

[Oleg Nesterov <oleg@tv-sign.ru>]

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>

--- 2.6.18-rc4/kernel/futex.c~2_ffgt	2006-08-21 20:32:48.000000000 +0400
+++ 2.6.18-rc4/kernel/futex.c	2006-08-21 20:41:15.000000000 +0400
@@ -389,7 +389,7 @@ static struct task_struct * futex_find_g
 {
 	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_g
 	}
 	get_task_struct(p);
 out_unlock:
-	read_unlock(&tasklist_lock);
+	rcu_read_unlock();
 
 	return p;
 }

-
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