From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754832Ab2DZVKu (ORCPT ); Thu, 26 Apr 2012 17:10:50 -0400 Received: from mail-pz0-f51.google.com ([209.85.210.51]:40199 "EHLO mail-pz0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751770Ab2DZVKt (ORCPT ); Thu, 26 Apr 2012 17:10:49 -0400 Date: Thu, 26 Apr 2012 14:10:42 -0700 From: Tejun Heo To: Sasha Levin Cc: axboe@kernel.dk, "linux-kernel@vger.kernel.org" , paulmck@linux.vnet.ibm.com Subject: [PATCH block/for-3.5/core] blkcg: tg_stats_alloc_lock is an irq lock Message-ID: <20120426211042.GC27486@google.com> References: <1335339396.16988.80.camel@lappy> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1335339396.16988.80.camel@lappy> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org tg_stats_alloc_lock nests inside queue lock and should always be held with irq disabled. throtl_pd_{init|exit}() were using non-irqsafe spinlock ops which triggered inverse lock ordering via irq warning via RCU freeing of blkg invoking throtl_pd_exit() w/o disabling IRQ. Update both functions to use irq safe operations. Signed-off-by: Tejun Heo Reported-by: Sasha Levin LKML-Reference: <1335339396.16988.80.camel@lappy> --- block/blk-throttle.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) Index: work/block/blk-throttle.c =================================================================== --- work.orig/block/blk-throttle.c +++ work/block/blk-throttle.c @@ -219,6 +219,7 @@ alloc_stats: static void throtl_pd_init(struct blkcg_gq *blkg) { struct throtl_grp *tg = blkg_to_tg(blkg); + unsigned long flags; RB_CLEAR_NODE(&tg->rb_node); bio_list_init(&tg->bio_lists[0]); @@ -235,19 +236,20 @@ static void throtl_pd_init(struct blkcg_ * but percpu allocator can't be called from IO path. Queue tg on * tg_stats_alloc_list and allocate from work item. */ - spin_lock(&tg_stats_alloc_lock); + spin_lock_irqsave(&tg_stats_alloc_lock, flags); list_add(&tg->stats_alloc_node, &tg_stats_alloc_list); queue_delayed_work(system_nrt_wq, &tg_stats_alloc_work, 0); - spin_unlock(&tg_stats_alloc_lock); + spin_unlock_irqrestore(&tg_stats_alloc_lock, flags); } static void throtl_pd_exit(struct blkcg_gq *blkg) { struct throtl_grp *tg = blkg_to_tg(blkg); + unsigned long flags; - spin_lock(&tg_stats_alloc_lock); + spin_lock_irqsave(&tg_stats_alloc_lock, flags); list_del_init(&tg->stats_alloc_node); - spin_unlock(&tg_stats_alloc_lock); + spin_unlock_irqrestore(&tg_stats_alloc_lock, flags); free_percpu(tg->stats_cpu); }