linux-kernel - [PATCH 2/2] k_getrusage: don't take rcu_read

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Message-ID: <20080218170737.GA2715@tv-sign.ru>
Date:	Mon, 18 Feb 2008 20:07:37 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] k_getrusage: don't take rcu_read_lock()

(just a trivial example, more to come)

k_getrusage() holds rcu_read_lock() because it was previously required by
lock_task_sighand(). Unneeded now.

Signed-off-by: Oleg Nesterov <oleg@...sign.ru>

--- 25/kernel/sys.c~2_GRU	2008-02-15 16:59:17.000000000 +0300
+++ 25/kernel/sys.c	2008-02-18 19:15:40.000000000 +0300
@@ -1548,11 +1548,8 @@ static void k_getrusage(struct task_stru
 	memset((char *) r, 0, sizeof *r);
 	utime = stime = cputime_zero;
 
-	rcu_read_lock();
-	if (!lock_task_sighand(p, &flags)) {
-		rcu_read_unlock();
+	if (!lock_task_sighand(p, &flags))
 		return;
-	}
 
 	switch (who) {
 		case RUSAGE_BOTH:
@@ -1595,9 +1592,7 @@ static void k_getrusage(struct task_stru
 		default:
 			BUG();
 	}
-
 	unlock_task_sighand(p, &flags);
-	rcu_read_unlock();
 
 	cputime_to_timeval(utime, &r->ru_utime);
 	cputime_to_timeval(stime, &r->ru_stime);

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