linux-kernel - Re: [merged] mm-mempolicyc-add-rcu-read-lock-to-protect-pid-structure.patch removed from -mm tree

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Message-Id: <20101208160009.173F.A69D9226@jp.fujitsu.com>
Date:	Wed,  8 Dec 2010 16:02:26 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	akpm@...ux-foundation.org
Cc:	kosaki.motohiro@...fujitsu.com, zengzm.kernel@...il.com,
	cl@...ux-foundation.org, paulmck@...ibm.com,
	mm-commits@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [merged] mm-mempolicyc-add-rcu-read-lock-to-protect-pid-structure.patch removed from -mm tree

> 
> The patch titled
>      mm/mempolicy.c: add rcu read lock to protect pid structure
> has been removed from the -mm tree.  Its filename was
>      mm-mempolicyc-add-rcu-read-lock-to-protect-pid-structure.patch
> 
> This patch was dropped because it was merged into mainline or a subsystem tree
> 
> The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
> 
> ------------------------------------------------------
> Subject: mm/mempolicy.c: add rcu read lock to protect pid structure
> From: Zeng Zhaoming <zengzm.kernel@...il.com>
> 
> find_task_by_vpid() should be protected by rcu_read_lock(), to prevent
> free_pid() reclaiming pid.
> 
> Signed-off-by: Zeng Zhaoming <zengzm.kernel@...il.com>
> Cc: "Paul E. McKenney" <paulmck@...ibm.com>
> Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Cc: Christoph Lameter <cl@...ux-foundation.org>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>


Andrew, please consider pick following patch too.



===========================================================================
>From 9de9f70f74e55d92b5e9057e22fc629405f63295 Mon Sep 17 00:00:00 2001
From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Date: Thu, 16 Dec 2010 17:49:23 +0900
Subject: [PATCH] mempolicy: remove tasklist_lock from migrate_pages

Today, tasklist_lock in migrate_pages doesn't protect anything. 
rcu_read_lock() provide enough protection from pid hash walk.

Reported-by: Peter Zijlstra <peterz@...radead.org>
Cc: Christoph Lameter <cl@...ux-foundation.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
---
 mm/mempolicy.c |    3 ---
 1 files changed, 0 insertions(+), 3 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 11ff260..9064945 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1308,16 +1308,13 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode,
 
 	/* Find the mm_struct */
 	rcu_read_lock();
-	read_lock(&tasklist_lock);
 	task = pid ? find_task_by_vpid(pid) : current;
 	if (!task) {
-		read_unlock(&tasklist_lock);
 		rcu_read_unlock();
 		err = -ESRCH;
 		goto out;
 	}
 	mm = get_task_mm(task);
-	read_unlock(&tasklist_lock);
 	rcu_read_unlock();
 
 	err = -EINVAL;
-- 
1.6.5.2



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