From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id C06226B0088 for ; Wed, 3 Feb 2010 15:09:07 -0500 (EST) Subject: Re: [RFC][PATCH] vmscan: balance local_irq_disable() and local_irq_enable() From: Steven Rostedt Reply-To: rostedt@goodmis.org In-Reply-To: <1265226801-6199-2-git-send-email-jkacur@redhat.com> References: <1265226801-6199-1-git-send-email-jkacur@redhat.com> <1265226801-6199-2-git-send-email-jkacur@redhat.com> Content-Type: text/plain; charset="ISO-8859-15" Date: Wed, 03 Feb 2010 15:09:06 -0500 Message-ID: <1265227746.24386.15.camel@gandalf.stny.rr.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: John Kacur Cc: lkml , Thomas Gleixner , Ingo Molnar , Andrew Morton , KOSAKI Motohiro , Rik van Riel , Johannes Weiner , Minchan Kim , linux-mm@kvack.org List-ID: t On Wed, 2010-02-03 at 20:53 +0100, John Kacur wrote: > Balance local_irq_disable() and local_irq_enable() as well as > spin_lock_irq() and spin_lock_unlock_irq > > Signed-off-by: John Kacur > --- > mm/vmscan.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index c26986c..b895025 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1200,8 +1200,9 @@ static unsigned long shrink_inactive_list(unsigned long max_scan, > if (current_is_kswapd()) > __count_vm_events(KSWAPD_STEAL, nr_freed); > __count_zone_vm_events(PGSTEAL, zone, nr_freed); > + local_irq_enable(); > > - spin_lock(&zone->lru_lock); > + spin_lock_irq(&zone->lru_lock); > /* > * Put back any unfreeable pages. > */ The above looks wrong. I don't know the code, but just by looking at where the locking and interrupts are, I can take a guess. Lets add a little more of the code: local_irq_disable(); if (current_is_kswapd()) __count_vm_events(KSWAPD_STEAL, nr_freed); __count_zone_vm_events(PGSTEAL, zone, nr_freed); spin_lock(&zone->lru_lock); /* I'm guessing the __count_zone_vm_events and friends need interrupts disabled here, probably due to per cpu stuff. But if you enable interrupts before the spin_lock() you may let an interrupt come in and invalidate what was done above it. So no, I do not think enabling interrupts here is a good thing. -- Steve -- 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