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@linux.ibm.com Cc: stable@vger.kernel.org Fixes: b07a889e8335 ("block: move q->sysfs_lock and queue-freeze under show/store method") Signed-off-by: Bart Van Assche bvanassche@acm.org
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@linux.ibm.com