From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guoqing Jiang Subject: Re: Calling block ops when !TASK_RUNNING warning in raid1 Date: Thu, 30 Nov 2017 10:56:38 +0800 Message-ID: <840098d9-8e39-22b3-f903-bf046ab92b86@suse.com> References: <20171128175222.zntgvtxaa4kzbtlw@kernel.org> <87y3movcqp.fsf@notabene.neil.brown.name> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87y3movcqp.fsf@notabene.neil.brown.name> Content-Language: en-US Sender: linux-raid-owner@vger.kernel.org To: NeilBrown , Shaohua Li , Dennis Yang Cc: linux-raid List-Id: linux-raid.ids On 11/30/2017 08:20 AM, NeilBrown wrote: > On Tue, Nov 28 2017, Shaohua Li wrote: > >> On Tue, Nov 28, 2017 at 04:51:25PM +0800, Dennis Yang wrote: >>> Hi, >>> >>> We recently see the following kernel dump on raid1 with some kernel >>> debug option on. >>> >>> <4>[ 40.501369] ------------[ cut here ]------------ >>> <4>[ 40.501375] WARNING: CPU: 7 PID: 7477 at >>> kernel/sched/core.c:7404 __might_sleep+0xa2/0xb0() >>> <4>[ 40.501378] do not call blocking ops when !TASK_RUNNING; state=2 >>> set at [] prepare_to_wait_event+0x58/0x100 >>> <4>[ 40.501379] Modules linked in: dm_c2f(O) pl2303 usbserial >>> qm2_i2c(O) intel_ips drbd(O) flashcache(O) dm_tier_hro_algo >>> dm_thin_pool dm_bio_prison dm_persistent_data hal_netlink(O) k10temp >>> coretemp mlx4_en(O) mlx4_core(O) mlx_compat(O) igb e1000e(O) >>> mpt3sas(O) mpt2sas scsi_transport_sas raid_class usb_storage xhci_pci >>> xhci_hcd usblp uhci_hcd ehci_pci ehci_hcd >>> <4>[ 40.501395] CPU: 7 PID: 7477 Comm: md321_resync Tainted: G >>> O 4.2.8 #1 >>> <4>[ 40.501396] Hardware name: INSYDE QV96/Type2 - Board Product >>> Name1, BIOS QV96IR23 10/21/2015 >>> <4>[ 40.501397] ffffffff8219aff7 ffff880092f7b868 ffffffff81c86c4b >>> ffffffff810dfb59 >>> <4>[ 40.501399] ffff880092f7b8b8 ffff880092f7b8a8 ffffffff81079fa5 >>> ffff880092f7b8e8 >>> <4>[ 40.501401] ffffffff821a4f6d 0000000000000140 0000000000000000 >>> 0000000000000001 >>> <4>[ 40.501403] Call Trace: >>> <4>[ 40.501407] [] dump_stack+0x4c/0x65 >>> <4>[ 40.501409] [] ? console_unlock+0x279/0x4f0 >>> <4>[ 40.501411] [] warn_slowpath_common+0x85/0xc0 >>> <4>[ 40.501412] [] warn_slowpath_fmt+0x41/0x50 >>> <4>[ 40.501414] [] ? prepare_to_wait_event+0x58/0x100 >>> <4>[ 40.501415] [] ? prepare_to_wait_event+0x58/0x100 >>> <4>[ 40.501416] [] __might_sleep+0xa2/0xb0 >>> <4>[ 40.501419] [] mempool_alloc+0x7c/0x150 >>> <4>[ 40.501422] [] ? save_stack_trace+0x2a/0x50 >>> <4>[ 40.501425] [] bio_alloc_bioset+0xb9/0x260 >>> <4>[ 40.501428] [] bio_alloc_mddev+0x1a/0x30 >>> <4>[ 40.501429] [] md_super_write+0x32/0x90 >>> <4>[ 40.501431] [] write_page+0x2d2/0x480 >>> <4>[ 40.501432] [] ? write_page+0x128/0x480 >>> <4>[ 40.501434] [] ? flush_pending_writes+0x1c/0xe0 >>> <4>[ 40.501435] [] bitmap_unplug+0x156/0x170 >>> <4>[ 40.501437] [] ? trace_hardirqs_on+0xd/0x10 >>> <4>[ 40.501439] [] ? _raw_spin_unlock_irq+0x2b/0x40 >>> <4>[ 40.501440] [] flush_pending_writes+0x63/0xe0 >>> <4>[ 40.501442] [] freeze_array+0x6f/0xc0 >>> <4>[ 40.501443] [] ? wait_woken+0xb0/0xb0 >>> <4>[ 40.501444] [] raid1_quiesce+0x3f/0x50 >>> <4>[ 40.501446] [] md_do_sync+0x1394/0x13b0 >>> <4>[ 40.501447] [] ? md_do_sync+0x671/0x13b0 >>> <4>[ 40.501449] [] ? __lock_acquire+0x990/0x23a0 >>> <4>[ 40.501451] [] ? pick_next_task_fair+0x707/0xc30 >>> <4>[ 40.501453] [] ? kernel_sigaction+0x2c/0xc0 >>> <4>[ 40.501455] [] ? _raw_spin_unlock_irq+0x2b/0x40 >>> <4>[ 40.501456] [] ? find_pers+0x80/0x80 >>> <4>[ 40.501457] [] md_thread+0x13e/0x150 >>> <4>[ 40.501458] [] ? find_pers+0x80/0x80 >>> <4>[ 40.501460] [] ? find_pers+0x80/0x80 >>> <4>[ 40.501462] [] kthread+0x105/0x120 >>> <4>[ 40.501463] [] ? _raw_spin_unlock_irq+0x2b/0x40 >>> <4>[ 40.501465] [] ? kthread_create_on_node+0x220/0x220 >>> <4>[ 40.501467] [] ret_from_fork+0x3f/0x70 >>> <4>[ 40.501468] [] ? kthread_create_on_node+0x220/0x220 >>> <4>[ 40.501469] ---[ end trace bd085fb137be2a87 ]--- >>> >>> It looks like raid1_quiesce() creates a nested sleeping primitives by >>> calling wait_event_lock_irq_cmd() >>> first to change the state to TASK_UNINTERRUPTIBLE and >>> flush_pending_writes() could eventually try >>> to allocate bio for bitmap update with GFP_NOIO which might sleep and >>> triggers this warning. >>> I am not sure if this warning is just a false-positive or should we >>> change the bio allocation >>> gfp flag to GFP_NOWAIT to prevent it from blocking? >> This is a legit warnning. Changing gfp to GFP_NOWAIT doesn't completely fix the >> issue, because generic_make_request could sleep too. I think we should move the >> work to a workqueue. Could you please try below patch (untested yet)? > I think it would be simpler to call __set_current_state(TASK_RUNNING) > in the 'then' branch of flush_pending_writes(). There is no 'then' branch in this function, maybe you mean set TASK_RUNNING in the 'if' branch, since the calltrace is triggered by flush_pending_writes -> flush_bio_list -> bitmap_unplug. Thanks, Guoqing