On 6/27/25 2:07 AM, Bart Van Assche wrote:
> Every time I run test srp/002 the following deadlock is triggered:
>
> task:multipathd
> Call Trace:
> <TASK>
> __schedule+0x8c1/0x1bf0
> schedule+0xdd/0x270
> schedule_preempt_disabled+0x1c/0x30
> __mutex_lock+0xb89/0x1650
> mutex_lock_nested+0x1f/0x30
> dm_table_set_restrictions+0x823/0xdf0
> __bind+0x166/0x590
> dm_swap_table+0x2a7/0x490
> do_resume+0x1b1/0x610
> dev_suspend+0x55/0x1a0
> ctl_ioctl+0x3a5/0x7e0
> dm_ctl_ioctl+0x12/0x20
> __x64_sys_ioctl+0x127/0x1a0
> x64_sys_call+0xe2b/0x17d0
> do_syscall_64+0x96/0x3a0
> entry_SYSCALL_64_after_hwframe+0x4b/0x53
> </TASK>
> task:(udev-worker)
> Call Trace:
> <TASK>
> __schedule+0x8c1/0x1bf0
> schedule+0xdd/0x270
> blk_mq_freeze_queue_wait+0xf2/0x140
> blk_mq_freeze_queue_nomemsave+0x23/0x30
> queue_ra_store+0x14e/0x290
> queue_attr_store+0x23e/0x2c0
> sysfs_kf_write+0xde/0x140
> kernfs_fop_write_iter+0x3b2/0x630
> vfs_write+0x4fd/0x1390
> ksys_write+0xfd/0x230
> __x64_sys_write+0x76/0xc0
> x64_sys_call+0x276/0x17d0
> do_syscall_64+0x96/0x3a0
> entry_SYSCALL_64_after_hwframe+0x4b/0x53
> </TASK>
>
> This deadlock happens because blk_mq_freeze_queue_nomemsave() waits for
> pending requests to finish. The pending requests do never complete because
> the dm-multipath queue_if_no_path option is enabled and the only path in
> the dm-multipath configuration is being removed.
>
> Fix this deadlock by removing the queue freezing/unfreezing code from
> queue_ra_store().
>
> Freezing the request queue from inside a block layer sysfs store callback
> function is essential when modifying parameters that affect how bios or
> requests are processed, e.g. parameters that affect bio_split_to_limit().
> Freezing the request queue when modifying parameters that do not affect bio
> nor request processing is not necessary.
>
> Cc: Nilay Shroff <nilay@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: b07a889e8335 ("block: move q->sysfs_lock and queue-freeze under show/store method")
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
> ---
I hope we'd address other sysfs store attributes requiring queue-freeze
in another patch. So with that,
Looks good to me:
Reviewed-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>
