On 3/14/23 16:00, Alexey Klimov wrote:
The delay is found to be in device's ->shutdown() methods called from kernel_restart():
void kernel_restart_prepare(char *cmd)
{
blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
system_state = SYSTEM_RESTART;
usermodehelper_disable();
device_shutdown(); <---- here
}
The driver in question is ufshcd and its ufshcd_wl_shutdown() shutdown method. It often blocks on scsi_device_quiesce() and upon manual checking it seems that it sleeps on blk_mq_freeze_queue_wait()/wait_event() in blk_freeze_queue():
scsi_device_quiesce(struct scsi_device *sdev)
{
...
blk_mq_freeze_queue(q);
...
}
||
V
void blk_freeze_queue(struct request_queue *q)
{
/*
* In the !blk_mq case we are only calling this to kill the
* q_usage_counter, otherwise this increases the freeze depth
* and waits for it to return to zero. For this reason there is
* no blk_unfreeze_queue(), and blk_freeze_queue() is not
* exported to drivers as the only user for unfreeze is blk_mq.
*/
blk_freeze_queue_start(q);
blk_mq_freeze_queue_wait(q); <--- sleeps on wait_event() here
}
Please let me know if you want me to resubmit patch "scsi: ufs: Remove
the LUN quiescing code from ufshcd_wl_shutdown()"
(https://lore.kernel.org/linux-scsi/20220331223424.1054715-14-bvanassche@xxxxxxx/).
Thanks,
Bart.
