linux-kernel - Re: [PATCH] [media] s5p-jpeg: fix recursive spinlock acquisition

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Date:   Mon, 29 May 2017 21:08:26 +0200
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     Alexandre Courbot <acourbot@...omium.org>,
        Andrzej Pietrasiewicz <andrzej.p@...sung.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [media] s5p-jpeg: fix recursive spinlock acquisition

Hi Mauro,

This patch seems to have lost somehow. Could you help merging it?

Thanks,
Jacek Anaszewski

On 05/29/2017 09:29 AM, Alexandre Courbot wrote:
> Hi everyone,
> 
> On Thu, Apr 27, 2017 at 4:35 AM, Jacek Anaszewski
> <jacek.anaszewski@...il.com> wrote:
>> On 04/26/2017 04:54 AM, Alexandre Courbot wrote:
>>> On Wed, Apr 26, 2017 at 4:15 AM, Jacek Anaszewski
>>> <jacek.anaszewski@...il.com> wrote:
>>>> Hi Alexandre,
>>>>
>>>> Thanks for the patch.
>>>>
>>>> On 04/25/2017 08:19 AM, Alexandre Courbot wrote:
>>>>> v4l2_m2m_job_finish(), which is called from the interrupt handler withHi s
>>>>> slock acquired, can call the device_run() hook immediately if another
>>>>> context was in the queue. This hook also acquires slock, resulting in
>>>>> a deadlock for this scenario.
>>>>>
>>>>> Fix this by releasing slock right before calling v4l2_m2m_job_finish().
>>>>> This is safe to do as the state of the hardware cannot change before
>>>>> v4l2_m2m_job_finish() is called anyway.
>>>>>
>>>>> Signed-off-by: Alexandre Courbot <acourbot@...omium.org>
>>>>> ---
>>>>>  drivers/media/platform/s5p-jpeg/jpeg-core.c | 12 +++++++++---
>>>>>  1 file changed, 9 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/drivers/media/platform/s5p-jpeg/jpeg-core.c b/drivers/media/platform/s5p-jpeg/jpeg-core.c
>>>>> index 52dc7941db65..223b4379929e 100644
>>>>> --- a/drivers/media/platform/s5p-jpeg/jpeg-core.c
>>>>> +++ b/drivers/media/platform/s5p-jpeg/jpeg-core.c
>>>>> @@ -2642,13 +2642,13 @@ static irqreturn_t s5p_jpeg_irq(int irq, void *dev_id)
>>>>>       if (curr_ctx->mode == S5P_JPEG_ENCODE)
>>>>>               vb2_set_plane_payload(&dst_buf->vb2_buf, 0, payload_size);
>>>>>       v4l2_m2m_buf_done(dst_buf, state);
>>>>> -     v4l2_m2m_job_finish(jpeg->m2m_dev, curr_ctx->fh.m2m_ctx);
>>>>>
>>>>>       curr_ctx->subsampling = s5p_jpeg_get_subsampling_mode(jpeg->regs);
>>>>>       spin_unlock(&jpeg->slock);
>>>>>
>>>>>       s5p_jpeg_clear_int(jpeg->regs);
>>>>>
>>>>> +     v4l2_m2m_job_finish(jpeg->m2m_dev, curr_ctx->fh.m2m_ctx);
>>>>>       return IRQ_HANDLED;
>>>>>  }
>>>>>
>>>>> @@ -2707,11 +2707,12 @@ static irqreturn_t exynos4_jpeg_irq(int irq, void *priv)
>>>>>               v4l2_m2m_buf_done(dst_vb, VB2_BUF_STATE_ERROR);
>>>>>       }
>>>>>
>>>>> -     v4l2_m2m_job_finish(jpeg->m2m_dev, curr_ctx->fh.m2m_ctx);
>>>>>       if (jpeg->variant->version == SJPEG_EXYNOS4)
>>>>>               curr_ctx->subsampling = exynos4_jpeg_get_frame_fmt(jpeg->regs);
>>>>>
>>>>>       spin_unlock(&jpeg->slock);
>>>>> +
>>>>> +     v4l2_m2m_job_finish(jpeg->m2m_dev, curr_ctx->fh.m2m_ctx);
>>>>>       return IRQ_HANDLED;
>>>>>  }
>>>>>
>>>>> @@ -2770,10 +2771,15 @@ static irqreturn_t exynos3250_jpeg_irq(int irq, void *dev_id)
>>>>>       if (curr_ctx->mode == S5P_JPEG_ENCODE)
>>>>>               vb2_set_plane_payload(&dst_buf->vb2_buf, 0, payload_size);
>>>>>       v4l2_m2m_buf_done(dst_buf, state);
>>>>> -     v4l2_m2m_job_finish(jpeg->m2m_dev, curr_ctx->fh.m2m_ctx);
>>>>>
>>>>>       curr_ctx->subsampling =
>>>>>                       exynos3250_jpeg_get_subsampling_mode(jpeg->regs);
>>>>> +
>>>>> +     spin_unlock(&jpeg->slock);
>>>>> +
>>>>> +     v4l2_m2m_job_finish(jpeg->m2m_dev, curr_ctx->fh.m2m_ctx);
>>>>> +     return IRQ_HANDLED;
>>>>> +
>>>>>  exit_unlock:
>>>>>       spin_unlock(&jpeg->slock);
>>>>>       return IRQ_HANDLED;
>>>>>
>>>>
>>>> Acked-by: Jacek Anaszewski <jacek.anaszewski@...il.com>
>>>>
>>>> Just out of curiosity - could you share how you discovered the problem -
>>>> by some static checkers or trying to use the driver?
>>>
>>> We discovered this issue after adding a new unit test for the jpeg
>>> codec in Chromium OS:
>>>
>>> https://bugs.chromium.org/p/chromium/issues/detail?id=705971
>>>
>>> >From what I understand the test spawns different processes that access
>>> the codec device concurrently, creating the situation leading to the
>>> bug.
>>
>> Thanks for the explanation. Nice fix.
> 
> Gentle ping as I am not seeing this patch in the tree yet. Thanks.
> 
>>
>>> On a slightly related note, I was thinking whether it would make sense
>>> to move the call to  v4l2_m2m_job_finish() (and maybe other parts of
>>> the current interrupt handler) into a worker or a threaded interrupt
>>> handler so as to reduce the time we spend with interrupts disabled.
>>> Can I have your input on this idea?
>>
>> Right, all remaining drivers call it from workers.
>> Feel free to submit a patch.
>>
>> --
>> Best regards,
>> Jacek Anaszewski
>