From: Hannes Reinecke <hare@suse.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
linux-block@vger.kernel.org,
Linux Kernel Mailinglist <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] block/genhd: use atomic_t for disk_event->block
Date: Tue, 1 Jun 2021 15:41:35 +0200 [thread overview]
Message-ID: <73783f6f-a3ec-907f-ea19-966e9d1457dc@suse.de> (raw)
In-Reply-To: <YLY1V/dTMeo3RGZd@T590>
On 6/1/21 3:25 PM, Ming Lei wrote:
> On Tue, Jun 01, 2021 at 01:01:45PM +0200, Hannes Reinecke wrote:
>> __disk_unblock_events() will call queue_delayed_work() with a '0' argument
>> under a spin lock. This might cause the queue_work item to be executed
>> immediately, and run into a deadlock in disk_check_events() waiting for
>> the lock to be released.
>
> Do you have lockdep warning on this 'deadlock'?
>
> Executed immediately doesn't mean the work fn is run in the current
> task context, and it is actually run in one wq worker(task) context, so
> __queue_work() usually wakes up one wq worker for running the work fn,
> then there shouldn't be the 'deadlock' you mentioned.
>
That's what I thought, too, but then we have a customer report
complaining about a stuck installation, and this kernel message:
> [ 990.305908] INFO: task init:1 blocked for more than 491 seconds.
> [ 990.311904] Not tainted 5.3.18-22-default #1
> [ 990.316682] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
> [ 990.324483] init D 0 1 0 0x00000000
> [ 990.329950] Call Trace:
> [ 990.332396] __schedule+0x28a/0x6d0
> [ 990.335876] ? work_busy+0x80/0x80
> [ 990.339267] schedule+0x2f/0xa0
> [ 990.342399] schedule_timeout+0x1dd/0x300
> [ 990.346399] ? check_preempt_curr+0x29/0x80
> [ 990.350569] ? ttwu_do_wakeup+0x19/0x150
> [ 990.354480] ? work_busy+0x80/0x80
> [ 990.357869] wait_for_completion+0xba/0x140
> [ 990.362040] ? wake_up_q+0xa0/0xa0
> [ 990.365430] __flush_work+0x177/0x1d0
> [ 990.369080] ? worker_detach_from_pool+0xa0/0xa0
> [ 990.373682] __cancel_work_timer+0x12b/0x1b0
> [ 990.377940] ? exact_lock+0xd/0x20
> [ 990.381329] ? kobj_lookup+0x113/0x160
> [ 990.385067] disk_block_events+0x78/0x90
> [ 990.388979] __blkdev_get+0x6d/0x7e0
> [ 990.392542] ? blkdev_get_by_dev+0x40/0x40
> [ 990.396627] do_dentry_open+0x1ea/0x380
> [ 990.400450] path_openat+0x2fc/0x1520
> [ 990.404103] do_filp_open+0x9b/0x110
> [ 990.407667] ? kmem_cache_alloc+0x3d/0x250
> [ 990.411749] ? do_sys_open+0x1bd/0x250
> [ 990.415486] do_sys_open+0x1bd/0x250
> [ 990.419052] do_syscall_64+0x5b/0x1e0
> [ 990.422701] entry_SYSCALL_64_after_hwframe+0x44/0xa9
Which does vanish with this patch.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions Germany GmbH, 90409 Nürnberg
GF: F. Imendörffer, HRB 36809 (AG Nürnberg)
next prev parent reply other threads:[~2021-06-01 13:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-01 11:01 [PATCH] block/genhd: use atomic_t for disk_event->block Hannes Reinecke
2021-06-01 13:25 ` Ming Lei
2021-06-01 13:41 ` Hannes Reinecke [this message]
2021-06-02 5:40 ` [block/genhd] 8107f5f540: WARNING:bad_unlock_balance_detected kernel test robot
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