Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751950AbbHGKPf (ORCPT ); Fri, 7 Aug 2015 06:15:35 -0400 Received: from mail-pa0-f50.google.com ([209.85.220.50]:35005 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751887AbbHGKPe (ORCPT ); Fri, 7 Aug 2015 06:15:34 -0400 Date: Fri, 7 Aug 2015 19:16:10 +0900 From: Sergey Senozhatsky To: Andrew Morton Cc: Joonsoo Kim , Sergey Senozhatsky , Minchan Kim , Nitin Gupta , linux-kernel@vger.kernel.org, Joonsoo Kim Subject: Re: [PATCH] zram: fix possible race when checking idle_strm Message-ID: <20150807101610.GA26678@swordfish> References: <1438934609-16924-1-git-send-email-iamjoonsoo.kim@lge.com> <20150807093720.GN1891@swordfish> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150807093720.GN1891@swordfish> User-Agent: Mutt/1.5.23+102 (2ca89bed6448) (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2428 Lines: 69 On (08/07/15 18:37), Sergey Senozhatsky wrote: [..] > > Signed-off-by: Joonsoo Kim > > Acked-by: Sergey Senozhatsky Andrew, my apologies, can we hold on a bit with my Acked-by. I need more time to think about the issue -- do we actually have one or we don't. It seems that to be on a safe side this check is better be done under the lock, but at the same time I sort of fail to convenience myself that doing this check outside the lock introduces any danger. Need some rest. May be Joonsoo and Minchan can add some bits (that I currently miss) or thoughts. -ss > > --- > > drivers/block/zram/zcomp.c | 15 +++++++++++++-- > > 1 file changed, 13 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c > > index 80a62e7..837e9c3 100644 > > --- a/drivers/block/zram/zcomp.c > > +++ b/drivers/block/zram/zcomp.c > > @@ -76,6 +76,17 @@ static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp) > > return zstrm; > > } > > > > +static bool avail_idle_strm(struct zcomp_strm_multi *zs) > > +{ > > + int avail; > > + > > + spin_lock(&zs->strm_lock); > > + avail = !list_empty(&zs->idle_strm); > > + spin_unlock(&zs->strm_lock); > > + > > + return avail; > > +} > > + > > /* > > * get idle zcomp_strm or wait until other process release > > * (zcomp_strm_release()) one for us > > @@ -97,7 +108,7 @@ static struct zcomp_strm *zcomp_strm_multi_find(struct zcomp *comp) > > /* zstrm streams limit reached, wait for idle stream */ > > if (zs->avail_strm >= zs->max_strm) { > > spin_unlock(&zs->strm_lock); > > - wait_event(zs->strm_wait, !list_empty(&zs->idle_strm)); > > + wait_event(zs->strm_wait, avail_idle_strm(zs)); > > continue; > > } > > /* allocate new zstrm stream */ > > @@ -109,7 +120,7 @@ static struct zcomp_strm *zcomp_strm_multi_find(struct zcomp *comp) > > spin_lock(&zs->strm_lock); > > zs->avail_strm--; > > spin_unlock(&zs->strm_lock); > > - wait_event(zs->strm_wait, !list_empty(&zs->idle_strm)); > > + wait_event(zs->strm_wait, avail_idle_strm(zs)); > > continue; > > } > > break; > > -- > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/