From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx110.postini.com [74.125.245.110]) by kanga.kvack.org (Postfix) with SMTP id 29E256B005A for ; Fri, 19 Oct 2012 15:15:39 -0400 (EDT) Received: by mail-ob0-f169.google.com with SMTP id va7so928684obc.14 for ; Fri, 19 Oct 2012 12:15:38 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <508110C4.6030805@jp.fujitsu.com> References: <20121017040515.GA13505@redhat.com> <20121017181413.GA16805@redhat.com> <20121017193229.GC16805@redhat.com> <20121017194501.GA24400@redhat.com> <507F803A.8000900@jp.fujitsu.com> <507F86BD.7070201@jp.fujitsu.com> <508110C4.6030805@jp.fujitsu.com> From: KOSAKI Motohiro Date: Fri, 19 Oct 2012 15:15:18 -0400 Message-ID: Subject: Re: [patch for-3.7 v3] mm, mempolicy: hold task->mempolicy refcount while reading numa_maps. Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Kamezawa Hiroyuki Cc: David Rientjes , Linus Torvalds , Andrew Morton , Dave Jones , bhutchings@solarflare.com, Konstantin Khlebnikov , Naoya Horiguchi , Hugh Dickins , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Fri, Oct 19, 2012 at 4:35 AM, Kamezawa Hiroyuki wrote: > (2012/10/19 5:03), David Rientjes wrote: >> >> On Thu, 18 Oct 2012, Kamezawa Hiroyuki wrote: >>> >>> @@ -132,7 +162,7 @@ static void *m_start(struct seq_file *m, loff_t *pos) >>> tail_vma = get_gate_vma(priv->task->mm); >>> priv->tail_vma = tail_vma; >>> - >>> + hold_task_mempolicy(priv); >>> /* Start with last addr hint */ >>> vma = find_vma(mm, last_addr); >>> if (last_addr && vma) { >>> @@ -159,6 +189,7 @@ out: >>> if (vma) >>> return vma; >>> + release_task_mempolicy(priv); >>> /* End of vmas has been reached */ >>> m->version = (tail_vma != NULL)? 0: -1UL; >>> up_read(&mm->mmap_sem); >> >> >> Otherwise looks good, but please remove the two task_lock()'s in >> show_numa_map() that I added as part of this since you're replacing the >> need for locking. >> > Thank you for your review. > How about this ? > > == > From c5849c9034abeec3f26bf30dadccd393b0c5c25e Mon Sep 17 00:00:00 2001 > From: KAMEZAWA Hiroyuki > Date: Fri, 19 Oct 2012 17:00:55 +0900 > Subject: [PATCH] hold task->mempolicy while numa_maps scans. > > /proc//numa_maps scans vma and show mempolicy under > mmap_sem. It sometimes accesses task->mempolicy which can > be freed without mmap_sem and numa_maps can show some > garbage while scanning. > > This patch tries to take reference count of task->mempolicy at reading > numa_maps before calling get_vma_policy(). By this, task->mempolicy > will not be freed until numa_maps reaches its end. > > Signed-off-by: KAMEZAWA Hiroyuki > > V2->v3 > - updated comments to be more verbose. > - removed task_lock() in numa_maps code. > V1->V2 > - access task->mempolicy only once and remember it. Becase kernel/exit.c > can overwrite it. > > Signed-off-by: KAMEZAWA Hiroyuki Acked-by: KOSAKI Motohiro -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org