From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Fri, 29 Sep 2006 09:00:55 +0000 (-0700)
Subject: [PATCH] sys_get_robust_list(): don't take tasklist_lock
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=aaa2a97eb9c0e91d7abc66bf76811a9599fdb3ee;p=linux-beck.git

[PATCH] sys_get_robust_list(): don't take tasklist_lock

use rcu locks for find_task_by_pid().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: 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 ca8ef11feb65..4b6770e9806d 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1624,7 +1624,7 @@ sys_get_robust_list(int pid, struct robust_list_head __user **head_ptr,
 		struct task_struct *p;
 
 		ret = -ESRCH;
-		read_lock(&tasklist_lock);
+		rcu_read_lock();
 		p = find_task_by_pid(pid);
 		if (!p)
 			goto err_unlock;
@@ -1633,7 +1633,7 @@ sys_get_robust_list(int pid, struct robust_list_head __user **head_ptr,
 				!capable(CAP_SYS_PTRACE))
 			goto err_unlock;
 		head = p->robust_list;
-		read_unlock(&tasklist_lock);
+		rcu_read_unlock();
 	}
 
 	if (put_user(sizeof(*head), len_ptr))
@@ -1641,7 +1641,7 @@ sys_get_robust_list(int pid, struct robust_list_head __user **head_ptr,
 	return put_user(head, head_ptr);
 
 err_unlock:
-	read_unlock(&tasklist_lock);
+	rcu_read_unlock();
 
 	return ret;
 }