From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754104AbbCBKdy (ORCPT ); Mon, 2 Mar 2015 05:33:54 -0500 Received: from mx1.redhat.com ([209.132.183.28]:54134 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753723AbbCBKdw (ORCPT ); Mon, 2 Mar 2015 05:33:52 -0500 From: Vitaly Kuznetsov To: "K. Y. Srinivasan" Cc: devel@linuxdriverproject.org, Haiyang Zhang , linux-kernel@vger.kernel.org, Dexuan Cui Subject: Re: [PATCH] Drivers: hv: hv_balloon: keep locks balanced on add_memory() failure References: <1424435367-26384-1-git-send-email-vkuznets@redhat.com> Date: Mon, 02 Mar 2015 11:33:41 +0100 In-Reply-To: <1424435367-26384-1-git-send-email-vkuznets@redhat.com> (Vitaly Kuznetsov's message of "Fri, 20 Feb 2015 13:29:27 +0100") Message-ID: <87h9u3eliy.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vitaly Kuznetsov writes: > When add_memory() fails the following BUG is observed: > [ 743.646107] hv_balloon: hot_add memory failed error is -17 > [ 743.679973] > [ 743.680930] ===================================== > [ 743.680930] [ BUG: bad unlock balance detected! ] > [ 743.680930] 3.19.0-rc5_bug1131426+ #552 Not tainted > [ 743.680930] ------------------------------------- > [ 743.680930] kworker/0:2/255 is trying to release lock (&dm_device.ha_region_mutex) at: > [ 743.680930] [] mutex_unlock+0xe/0x10 > [ 743.680930] but there are no more locks to release! > > This happens as we don't acquire ha_region_mutex and hot_add_req() expects us > to as it does unconditional mutex_unlock(). Acquire the lock on the error path. > > Signed-off-by: Vitaly Kuznetsov > --- > This patch is dependent on the previously posted 'Drivers: hv: hv_balloon: > eliminate the trylock path in acquire/release_region_mutex'. Hi K.Y., I don't see this patch in your '[PATCH 0/7] Drivers: hv: Collection fixes and enhancements' sent to Greg. Please let me know if you see any issues with it as it looks like a pretty important bugfix to me. Thanks, > --- > drivers/hv/hv_balloon.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c > index 1283035..771bf84 100644 > --- a/drivers/hv/hv_balloon.c > +++ b/drivers/hv/hv_balloon.c > @@ -654,6 +654,7 @@ static void hv_mem_hot_add(unsigned long start, unsigned long size, > } > has->ha_end_pfn -= HA_CHUNK; > has->covered_end_pfn -= processed_pfn; > + mutex_lock(&dm_device.ha_region_mutex); > break; > } -- Vitaly