From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755545AbbBLKYj (ORCPT ); Thu, 12 Feb 2015 05:24:39 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55384 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755509AbbBLKYh (ORCPT ); Thu, 12 Feb 2015 05:24:37 -0500 From: Vitaly Kuznetsov To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , "K. Y. Srinivasan" , Haiyang Zhang , Andrew Morton , Yasuaki Ishimatsu , Tang Chen , Vlastimil Babka , David Rientjes , Fabian Frederick , Zhang Zhen , Vladimir Davydov , Wang Nan , "Rafael J. Wysocki" , devel@linuxdriverproject.org, linux-mm@kvack.org Subject: [PATCH RESEND 3/3] Drivers: hv: balloon: fix deadlock between memory adding and onlining Date: Thu, 12 Feb 2015 11:23:54 +0100 Message-Id: <1423736634-338-4-git-send-email-vkuznets@redhat.com> In-Reply-To: <1423736634-338-1-git-send-email-vkuznets@redhat.com> References: <1423736634-338-1-git-send-email-vkuznets@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If newly added memory is brought online with e.g. udev rule: SUBSYSTEM=="memory", ACTION=="add", ATTR{state}="online" the following deadlock is observed (and easily reproducable): First participant, worker thread doing add_memory(): ... [ 725.491469] 6 locks held by kworker/0:1/27: [ 725.505037] #0: ("events"){......}, at: [] process_one_work+0x16d/0x4e0 [ 725.533370] #1: ((&dm_device.ha_wrk.wrk)){......}, at: [] process_one_work+0x16d/0x4e0 [ 725.565580] #2: (mem_hotplug.lock){......}, at: [] mem_hotplug_begin+0x5/0x80 [ 725.594369] #3: (mem_hotplug.lock#2){......}, at: [] mem_hotplug_begin+0x4f/0x80 [ 725.628554] #4: (mem_sysfs_mutex){......}, at: [] register_new_memory+0x33/0xd0 [ 725.658519] #5: (&dev->mutex){......}, at: [] device_attach+0x23/0xb0 Second participant, udev: ... [ 726.150691] 7 locks held by systemd-udevd/888: [ 726.165044] #0: (sb_writers#3){......}, at: [] vfs_write+0x1b3/0x1f0 [ 726.192422] #1: (&of->mutex){......}, at: [] kernfs_fop_write+0x66/0x1a0 [ 726.220289] #2: (s_active#60){......}, at: [] kernfs_fop_write+0x6e/0x1a0 [ 726.249382] #3: (device_hotplug_lock){......}, at: [] lock_device_hotplug_sysfs+0x15/0x50 [ 726.281901] #4: (&dev->mutex){......}, at: [] device_online+0x23/0xa0 [ 726.308619] #5: (mem_hotplug.lock){......}, at: [] mem_hotplug_begin+0x5/0x80 [ 726.337994] #6: (mem_hotplug.lock#2){......}, at: [] mem_hotplug_begin+0x4f/0x80 Solve the issue bu grabbing device_hotplug_lock before doing add_memory(). If we do that, lock_device_hotplug_sysfs() will cause syscall retry which will eventually succeed. Signed-off-by: Vitaly Kuznetsov --- drivers/hv/hv_balloon.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c index b958ded..0af1aa2 100644 --- a/drivers/hv/hv_balloon.c +++ b/drivers/hv/hv_balloon.c @@ -592,9 +592,19 @@ static void hv_mem_hot_add(unsigned long start, unsigned long size, dm_device.ha_waiting = true; nid = memory_add_physaddr_to_nid(PFN_PHYS(start_pfn)); + + /* + * Grab hotplug lock as we'll be doing device_register() and we + * need to protect against someone (e.g. udev doing memory + * onlining) locking it before we're done. + */ + lock_device_hotplug(); + ret = add_memory(nid, PFN_PHYS((start_pfn)), (HA_CHUNK << PAGE_SHIFT)); + unlock_device_hotplug(); + if (ret) { pr_info("hot_add memory failed error is %d\n", ret); if (ret == -EEXIST) { -- 1.9.3