linux-kernel - Re: [PATCH] tee: optee: remove need_resched() before cond

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Date:   Sun, 31 Jan 2021 09:13:48 +0100
From:   Rouven Czerwinski <r.czerwinski@...gutronix.de>
To:     Jens Wiklander <jens.wiklander@...aro.org>,
        Sumit Garg <sumit.garg@...aro.org>
Cc:     Arnd Bergmann <arnd@...nel.org>, op-tee@...ts.trustedfirmware.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tee: optee: remove need_resched() before cond_resched()

Hi Jens,

On 29.01.21 14:29, Jens Wiklander wrote:
> Hi Rouven and Sumit,
> 
> On Mon, Jan 25, 2021 at 10:58 AM Jens Wiklander via OP-TEE
> <op-tee@...ts.trustedfirmware.org> wrote:
>>
>> Hi Rouven and Sumit,
>>
>> On Mon, Jan 25, 2021 at 10:55 AM Jens Wiklander
>> <jens.wiklander@...aro.org> wrote:
>>>
>>> Testing need_resched() before cond_resched() is not needed as an
>>> equivalent test is done internally in cond_resched(). So drop the
>>> need_resched() test.
>>>
>>> Fixes: dcb3b06d9c34 ("tee: optee: replace might_sleep with cond_resched")
>>> Signed-off-by: Jens Wiklander <jens.wiklander@...aro.org>
>>> ---
>>>   drivers/tee/optee/call.c | 3 +--
>>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> Can you please test to see that this works in your setups too?
> 
> Does this work for you? I'd like to get this patch ready for v5.12.

Yes it does. I also looked at it right after Arnds mail, so for future 
reference:


cond_resched()

   _cond_resched() (ifndef CONFIG_PREEMPTION)

     should_resched(0)

       tif_need_resched() (+ preempt_count == 0 for current thread)



while:



need_resched()

   tif_need_resched()


You can add my
Reviewed-by: Rouven Czerwinski <r.czerwinski@...gutronix.de>

I also retested on the STM32-DK2 and the problem remains fixed:

Tested-by: Rouven Czerwinski <r.czerwinski@...gutronix.de>

Regrads and thanks for the patch,
Rouven