Hi Bart,
On 2020-08-01 00:51, Bart Van Assche wrote:
On 2020-07-31 01:00, Can Guo wrote:
AFAIK, sychronization of scsi_done is not a problem here, because scsi
layer
use the atomic state, namely SCMD_STATE_COMPLETE, of a scsi cmd to
prevent
the concurrency of abort and real completion of it.
Check func scsi_times_out(), hope it helps.
enum blk_eh_timer_return scsi_times_out(struct request *req)
{
...
if (rtn == BLK_EH_DONE) {
/*
* Set the command to complete first in order to
prevent
a real
* completion from releasing the command while error
handling
* is using it. If the command was already completed,
then the
* lower level driver beat the timeout handler, and it
is safe
* to return without escalating error recovery.
*
* If timeout handling lost the race to a real
completion, the
* block layer may ignore that due to a fake timeout
injection,
* so return RESET_TIMER to allow error handling
another
shot
* at this command.
*/
if (test_and_set_bit(SCMD_STATE_COMPLETE,
&scmd->state))
return BLK_EH_RESET_TIMER;
if (scsi_abort_command(scmd) != SUCCESS) {
set_host_byte(scmd, DID_TIME_OUT);
scsi_eh_scmd_add(scmd);
}
}
}
I am familiar with this mechanism. My concern is that both the regular
completion path and the abort handler must call scsi_dma_unmap() before
calling cmd->scsi_done(cmd). I don't see how
test_and_set_bit(SCMD_STATE_COMPLETE, &scmd->state) could prevent that
the regular completion path and the abort handler call scsi_dma_unmap()
concurrently since both calls happen before the SCMD_STATE_COMPLETE bit
is set?
Thanks,
Bart.
For scsi_dma_unmap() part, that is true - we should make it serialized
with
any other completion paths. I've found it during my fault injection
test, so
I've made a patch to fix it, but it only comes in my next error recovery
enhancement patch series. Please check the attachment.
Thanks,
Can Guo.
From ef87832b5f6ff6af29ac9bac7fdea1e245c8162b Mon Sep 17 00:00:00 2001
From: Can Guo <cang@xxxxxxxxxxxxxx>
Date: Sun, 7 Jun 2020 12:16:01 +0800
Subject: [PATCH 5/6] scsi: ufs: Properly release resources if a task is
aborted successfully
In current UFS task abort hook, namely ufshcd_abort(), if a task is
aborted successfully, clock scaling busy time statistics is not updated
and, most important, clk_gating.active_reqs is not decreased, which makes
clk_gating.active_reqs stay above zero forever, meaning clock gating would
never happen. To fix it, instead of releasing resources "mannually", use
the existing func __ufshcd_transfer_req_compl().
Change-Id: Ia8cc496f53bb428eac7cfa784e431a2b37a45375
Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 3c46f74..87b911f 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -6876,16 +6876,10 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
goto out;
}
- scsi_dma_unmap(cmd);
-
spin_lock_irqsave(host->host_lock, flags);
- ufshcd_outstanding_req_clear(hba, tag);
- hba->lrb[tag].cmd = NULL;
+ __ufshcd_transfer_req_compl(hba, (1UL << tag));
spin_unlock_irqrestore(host->host_lock, flags);
- clear_bit_unlock(tag, &hba->lrb_in_use);
- wake_up(&hba->dev_cmd.tag_wq);
-
out:
if (!err) {
err = SUCCESS;
--
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