On 2020-10-26 14:13, Jaegeuk Kim wrote:
On 10/26, Can Guo wrote:
On 2020-10-24 23:06, Jaegeuk Kim wrote:
> From: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
>
> When giving a stress test which enables/disables clkgating, we hit
> device
> timeout sometimes. This patch avoids subtle racy condition to address
> it.
>
> If we use __ufshcd_release(), I've seen that gate_work can be called in
> parallel
> with ungate_work, which results in UFS timeout when doing hibern8.
> Should avoid it.
>
I don't understand this comment. gate_work and ungate_work are queued
on
an ordered workqueue and an ordered workqueue executes at most one
work item
at any given time in the queued order. How can the two run in
parallel?
When I hit UFS stuck, I saw this by clkgating tracepoint.
- REQ_CLK_OFF
- CLKS_OFF
- REQ_CLK_OFF
- REQ_CLKS_ON
..
I don't see how can you tell that the two works are running in parallel
just from above trace. May I know what is the exact error by "UFS
timeout
when doing hibern8"?
By using __ufshcd_release() here, I do see one potential issue if your
test
quickly toggles on/off of clk_gating - disable it, enable it, disable it
and
enable it, which will cause that __ufshcd_release() being called twice,
meaning
we queue two gate_works back to back. So can you try below code and let
me know
if it helps or not? I am OK with your current change, but I would like
to
understand the problem. Thanks.
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 1791bce..3eee438 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -2271,6 +2271,8 @@ static void ufshcd_gate_work(struct work_struct
*work)
unsigned long flags;
spin_lock_irqsave(hba->host->host_lock, flags);
+ if (hba->clk_gating.state == CLKS_OFF)
+ goto rel_lock;
/*
* In case you are here to cancel this work the gating state
* would be marked as REQ_CLKS_ON. In this case save time by
Regards,
Can Guo.
By using active_req, I don't see any problem.
Thanks,
Can Guo.
> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> ---
> drivers/scsi/ufs/ufshcd.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index b8f573a02713..e0b479f9eb8a 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1807,19 +1807,19 @@ static ssize_t
> ufshcd_clkgate_enable_store(struct device *dev,
> return -EINVAL;
>
> value = !!value;
> +
> + spin_lock_irqsave(hba->host->host_lock, flags);
> if (value == hba->clk_gating.is_enabled)
> goto out;
>
> - if (value) {
> - ufshcd_release(hba);
> - } else {
> - spin_lock_irqsave(hba->host->host_lock, flags);
> + if (value)
> + hba->clk_gating.active_reqs--;
> + else
> hba->clk_gating.active_reqs++;
> - spin_unlock_irqrestore(hba->host->host_lock, flags);
> - }
>
> hba->clk_gating.is_enabled = value;
> out:
> + spin_unlock_irqrestore(hba->host->host_lock, flags);
> return count;
> }
