Re: [PATCH 8/8] scsi: ufs: Check for completion from the timeout handler

[Bart Van Assche <bvanassche@acm.org>]

On 6/24/24 1:54 AM, Peter Wang (王信友) wrote:
> Your backtrace is Single doorbell mode. But I am curious that
> how could it happen if complete a cmd twice and get null pointer
> next time queuecommand? could you describe the exactly flow?

SCSI commands are completed only once. See also the code in the SCSI
core that sets the SCMD_STATE_COMPLETE bit:

$ git grep -nH 'test_and_set_bit(SCMD_STATE_COMPLETE'
drivers/scsi/scsi_error.c:362:	if (test_and_set_bit(SCMD_STATE_COMPLETE, 
&scmd->state))
drivers/scsi/scsi_lib.c:1716:	if 
(unlikely(test_and_set_bit(SCMD_STATE_COMPLETE, &cmd->state)))

In other words, either the regular completion code is executed by
scsi_done_internal() or error handling is initiated by scsi_timeout().
Only one of the two happens.

The only exception is that .eh_timed_out() may be called concurrently
with the regular completion handler. Hence this patch for
ufshcd_eh_timed_out().

Bart.