[PATCH v1] scsi: ufs: core: Remove the ufshcd_release in ufshcd_err_handling_prepare

[PATCH v1] scsi: ufs: core: Remove the ufshcd_release in ufshcd_err_handling_prepare

[SEO HOYOUNG]

If err_handler is performed in the suspend/resume situation, ufs_release
can be called twice and active_reqs valid can be negative.
This is because ufshcd_errhandling_prepare() and
ufshcd_err_handling_unprepare() repeatedly release calls.
Eventually, active_reqs have a value different from the intention.
To prevent this, release duplication processing was removed.

Signed-off-by: SEO HOYOUNG <hy50.seo@samsung.com>
---
 drivers/ufs/core/ufshcd.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 7c59d7a02243..423e83074a20 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -6351,7 +6351,6 @@ static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
 		ufshcd_hold(hba);
 		if (!ufshcd_is_clkgating_allowed(hba))
 			ufshcd_setup_clocks(hba, true);
-		ufshcd_release(hba);
 		pm_op = hba->is_sys_suspended ? UFS_SYSTEM_PM : UFS_RUNTIME_PM;
 		ufshcd_vops_resume(hba, pm_op);
 	} else {
-- 
2.26.0

Re: [PATCH v1] scsi: ufs: core: Remove the ufshcd_release in ufshcd_err_handling_prepare

[Bart Van Assche]

On 1/22/24 00:33, SEO HOYOUNG wrote:
> If err_handler is performed in the suspend/resume situation, ufs_release
> can be called twice and active_reqs valid can be negative.
> This is because ufshcd_errhandling_prepare() and
> ufshcd_err_handling_unprepare() repeatedly release calls.
> Eventually, active_reqs have a value different from the intention.
> To prevent this, release duplication processing was removed.
> 
> Signed-off-by: SEO HOYOUNG <hy50.seo@samsung.com>
> ---
>   drivers/ufs/core/ufshcd.c | 1 -
>   1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 7c59d7a02243..423e83074a20 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -6351,7 +6351,6 @@ static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
>   		ufshcd_hold(hba);
>   		if (!ufshcd_is_clkgating_allowed(hba))
>   			ufshcd_setup_clocks(hba, true);
> -		ufshcd_release(hba);
>   		pm_op = hba->is_sys_suspended ? UFS_SYSTEM_PM : UFS_RUNTIME_PM;
>   		ufshcd_vops_resume(hba, pm_op);
>   	} else {

I think that the above ufshcd_release() call pairs with the ufshcd_hold()
call three lines above it and hence that removing that call would be
wrong.

Thanks,

Bart.

RE: [PATCH v1] scsi: ufs: core: Remove the ufshcd_release in ufshcd_err_handling_prepare

[hoyoung seo]

> -----Original Message-----
> From: Bart Van Assche <bvanassche@acm.org>
> Sent: Tuesday, January 23, 2024 5:37 AM
> To: SEO HOYOUNG <hy50.seo@samsung.com>; linux-scsi@vger.kernel.org; linux-
> kernel@vger.kernel.org; alim.akhtar@samsung.com; avri.altman@wdc.com;
> jejb@linux.ibm.com; martin.petersen@oracle.com; beanhuo@micron.com;
> kwangwon.min@samsung.com; kwmad.kim@samsung.com; sh425.lee@samsung.com;
> sc.suh@samsung.com; quic_nguyenb@quicinc.com; cpgs@samsung.com;
> grant.jung@samsung.com; junwoo80.lee@samsung.com
> Subject: Re: [PATCH v1] scsi: ufs: core: Remove the ufshcd_release in
> ufshcd_err_handling_prepare
> 
> On 1/22/24 00:33, SEO HOYOUNG wrote:
> > If err_handler is performed in the suspend/resume situation,
> > ufs_release can be called twice and active_reqs valid can be negative.
> > This is because ufshcd_errhandling_prepare() and
> > ufshcd_err_handling_unprepare() repeatedly release calls.
> > Eventually, active_reqs have a value different from the intention.
> > To prevent this, release duplication processing was removed.
> >
> > Signed-off-by: SEO HOYOUNG <hy50.seo@samsung.com>
> > ---
> >   drivers/ufs/core/ufshcd.c | 1 -
> >   1 file changed, 1 deletion(-)
> >
> > diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> > index 7c59d7a02243..423e83074a20 100644
> > --- a/drivers/ufs/core/ufshcd.c
> > +++ b/drivers/ufs/core/ufshcd.c
> > @@ -6351,7 +6351,6 @@ static void ufshcd_err_handling_prepare(struct
> ufs_hba *hba)
> >   		ufshcd_hold(hba);
> >   		if (!ufshcd_is_clkgating_allowed(hba))
> >   			ufshcd_setup_clocks(hba, true);
> > -		ufshcd_release(hba);
> >   		pm_op = hba->is_sys_suspended ? UFS_SYSTEM_PM :
> UFS_RUNTIME_PM;
> >   		ufshcd_vops_resume(hba, pm_op);
> >   	} else {
> 
> I think that the above ufshcd_release() call pairs with the ufshcd_hold()
> call three lines above it and hence that removing that call would be wrong.
> 
> Thanks,
> 
> Bart.

Hi,

It was a different when I tested it.
If __ufshcd_wl_resume() is called active_reqs is 1.
Because ufshcd_hold() is called in __ufshcd_wl_suspend().
If occurred hibern8_exit failed in __ufschd_wl_resume(), ufshcd_release()
is called in the :out syntax, and active_reqs becomes 0.
After that, active_reqs becomes 0 because ufshcd_hold() is called 
from ufshcd_err_handling_repare()and ufshcd_release() is called again while
err_handler is operating.
When err_handler is completed, active_reqs becomes negative because 
ufshcd_release() is called again in ufshcd_err_handling_unprepare().
I tested it while printing the log, and if I misanalyzed it, let me know.

Thanks,

SEO.

Re: [PATCH v1] scsi: ufs: core: Remove the ufshcd_release in ufshcd_err_handling_prepare

[Bart Van Assche]

On 1/22/24 18:38, hoyoung seo wrote:
> When err_handler is completed, active_reqs becomes negative because
> ufshcd_release() is called again in ufshcd_err_handling_unprepare().
> I tested it while printing the log, and if I misanalyzed it, let me know.

Please repeat your analysis. I think this patch is wrong.

Thanks,

Bart.

RE: [PATCH v1] scsi: ufs: core: Remove the ufshcd_release in ufshcd_err_handling_prepare

[hoyoung seo]

> -----Original Message-----
> From: Bart Van Assche <bvanassche@acm.org>
> Sent: Thursday, January 25, 2024 1:17 AM
> To: hoyoung seo <hy50.seo@samsung.com>; linux-scsi@vger.kernel.org; linux-
> kernel@vger.kernel.org; alim.akhtar@samsung.com; avri.altman@wdc.com;
> jejb@linux.ibm.com; martin.petersen@oracle.com; beanhuo@micron.com;
> kwangwon.min@samsung.com; kwmad.kim@samsung.com; sh425.lee@samsung.com;
> sc.suh@samsung.com; quic_nguyenb@quicinc.com; cpgs@samsung.com;
> grant.jung@samsung.com; junwoo80.lee@samsung.com
> Subject: Re: [PATCH v1] scsi: ufs: core: Remove the ufshcd_release in
> ufshcd_err_handling_prepare
> 
> On 1/22/24 18:38, hoyoung seo wrote:
> > When err_handler is completed, active_reqs becomes negative because
> > ufshcd_release() is called again in ufshcd_err_handling_unprepare().
> > I tested it while printing the log, and if I misanalyzed it, let me know.
> 
> Please repeat your analysis. I think this patch is wrong.
> 
> Thanks,
> 
> Bart.

Hi,

I do not understand. why you said my patch is wrong.
If ufs entered suspend with hibern8 state then the hba->clk_gating.active_reqs is 1.
After that run wl_resume(), ufs drvier send hibern8 exit command.
At that time, if the command timeout or error occurs, the err_handler is activated. 
Then the active_reqs pair may not fit.

So to sum up, ufs_release() is performed 3 time.
(wl_resume(), ufshcd_err_handling_prepare(), ufshcd_err_handling_unprepare())
And the ufshcd_hold() is performed 2 time(__ufshcd_wl_suspend(), ufshcd_err_handling_prepare())
So the paire of active_reqs is not correct.
So I deleted the ufshcd_release() in ufshcd_err_handling_prepare().

The ufshcd_release() was not called again even in the pm_op_in_progress state in 4.xx version of the kernel.
But now if is_sys_suspended is 1, then ufshcd_release() is called once more.
I don't understand why this is added and the pair doesn't fit.

Please check it again.
Thanks.

Seo.

Re: [PATCH v1] scsi: ufs: core: Remove the ufshcd_release in ufshcd_err_handling_prepare

[Bart Van Assche]

On 1/31/24 00:23, hoyoung seo wrote:
> I do not understand. why you said my patch is wrong.

My apologies - I misread the patch.

Bart.

Re: [PATCH v1] scsi: ufs: core: Remove the ufshcd_release in ufshcd_err_handling_prepare

[Bart Van Assche]

On 1/22/24 00:33, SEO HOYOUNG wrote:
> This is because ufshcd_errhandling_prepare() and
> ufshcd_err_handling_unprepare() repeatedly release calls.

It would have been much more clear if it would have been mentioned that
ufshcd_err_handling_prepare() should call ufshcd_hold() once and
also that ufshcd_err_handling_unprepare() should call ufshcd_release()
once.

Additionally, a Fixes: tag is missing. Is this patch perhaps a fix for commit
c72e79c0ad2b ("scsi: ufs: Recover HBA runtime PM error in error handler")?
Can Guo, since you wrote that patch, can you please take a look at this patch?

> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 7c59d7a02243..423e83074a20 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -6351,7 +6351,6 @@ static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
>   		ufshcd_hold(hba);
>   		if (!ufshcd_is_clkgating_allowed(hba))
>   			ufshcd_setup_clocks(hba, true);
> -		ufshcd_release(hba);
>   		pm_op = hba->is_sys_suspended ? UFS_SYSTEM_PM : UFS_RUNTIME_PM;
>   		ufshcd_vops_resume(hba, pm_op);
>   	} else {

Reviewed-by: Bart Van Assche <bvanassche@acm.org>

Re: [PATCH v1] scsi: ufs: core: Remove the ufshcd_release in ufshcd_err_handling_prepare

[Can Guo]

On 2/1/2024 1:44 AM, Bart Van Assche wrote:
> On 1/22/24 00:33, SEO HOYOUNG wrote:
>> This is because ufshcd_errhandling_prepare() and
>> ufshcd_err_handling_unprepare() repeatedly release calls.
> 
> It would have been much more clear if it would have been mentioned that
> ufshcd_err_handling_prepare() should call ufshcd_hold() once and
> also that ufshcd_err_handling_unprepare() should call ufshcd_release()
> once.
> 
> Additionally, a Fixes: tag is missing. Is this patch perhaps a fix for 
> commit
> c72e79c0ad2b ("scsi: ufs: Recover HBA runtime PM error in error handler")?
> Can Guo, since you wrote that patch, can you please take a look at this 
> patch?
> 
>> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
>> index 7c59d7a02243..423e83074a20 100644
>> --- a/drivers/ufs/core/ufshcd.c
>> +++ b/drivers/ufs/core/ufshcd.c
>> @@ -6351,7 +6351,6 @@ static void ufshcd_err_handling_prepare(struct 
>> ufs_hba *hba)
>>           ufshcd_hold(hba);
>>           if (!ufshcd_is_clkgating_allowed(hba))
>>               ufshcd_setup_clocks(hba, true);
>> -        ufshcd_release(hba);

When we are here, it means runtime resume has failed.

When I wrote the code (in older kernel), ufshcd_runtime_resume(), if 
fails, bails without calling ufshcd_release(), eventually 
ufshcd_err_handling_unprepare() would call ufshcd_release() to balance.

But now, I see that if __ufshcd_wl_resume() fails, ufshcd_release() is 
called anyways, so ufshcd_release() is not required here. Hence,

Reviewed-by: Can Guo <quic_cang@quicinc.com>

>>           pm_op = hba->is_sys_suspended ? UFS_SYSTEM_PM : UFS_RUNTIME_PM;
>>           ufshcd_vops_resume(hba, pm_op);
>>       } else {
> 
> Reviewed-by: Bart Van Assche <bvanassche@acm.org>

Re: [PATCH v1] scsi: ufs: core: Remove the ufshcd_release in ufshcd_err_handling_prepare

[Martin K. Petersen]

On Mon, 22 Jan 2024 17:33:24 +0900, SEO HOYOUNG wrote:

> If err_handler is performed in the suspend/resume situation, ufs_release
> can be called twice and active_reqs valid can be negative.
> This is because ufshcd_errhandling_prepare() and
> ufshcd_err_handling_unprepare() repeatedly release calls.
> Eventually, active_reqs have a value different from the intention.
> To prevent this, release duplication processing was removed.
> 
> [...]

Applied to 6.8/scsi-fixes, thanks!

[1/1] scsi: ufs: core: Remove the ufshcd_release in ufshcd_err_handling_prepare
      https://git.kernel.org/mkp/scsi/c/17e94b258541

-- 
Martin K. Petersen	Oracle Linux Engineering