linux-kernel - Re: [PATCH v2] media: mediatek: vcodec: Use spinlock for context list protection lock

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Message-ID: <a8775c16be8a904b94b62df5cf530321f7424c95.camel@ndufresne.ca>
Date: Thu, 04 Sep 2025 09:34:40 -0400
From: Nicolas Dufresne <nicolas@...fresne.ca>
To: Tomasz Figa <tfiga@...omium.org>, Chen-Yu Tsai <wenst@...omium.org>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>, Hans Verkuil	
 <hverkuil@...all.nl>, Yunfei Dong <yunfei.dong@...iatek.com>, Matthias
 Brugger	 <matthias.bgg@...il.com>, AngeloGioacchino Del Regno	
 <angelogioacchino.delregno@...labora.com>, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org, Fei Shao	
 <fshao@...omium.org>
Subject: Re: [PATCH v2] media: mediatek: vcodec: Use spinlock for context
 list protection lock

Hi,

Le jeudi 04 septembre 2025 à 15:39 +0900, Tomasz Figa a écrit :
> On Thu, Sep 4, 2025 at 3:18 PM Chen-Yu Tsai <wenst@...omium.org> wrote:
> > 
> > Ping?
> > 
> > On Wed, Aug 20, 2025 at 6:37 PM Fei Shao <fshao@...omium.org> wrote:
> > > 
> > > On Wed, Aug 20, 2025 at 3:54 PM Chen-Yu Tsai <wenst@...omium.org> wrote:
> > > > 
> > > > Previously a mutex was added to protect the encoder and decoder context
> > > > lists from unexpected changes originating from the SCP IP block, causing
> > > > the context pointer to go invalid, resulting in a NULL pointer
> > > > dereference in the IPI handler.
> > > > 
> > > > Turns out on the MT8173, the VPU IPI handler is called from hard IRQ
> > > > context. This causes a big warning from the scheduler. This was first
> > > > reported downstream on the ChromeOS kernels, but is also reproducible
> > > > on mainline using Fluster with the FFmpeg v4l2m2m decoders. Even though
> > > > the actual capture format is not supported, the affected code paths
> > > > are triggered.
> > > > 
> > 
> > We really should get this in as this triggers a very large and scary
> > warning every time the encoder or decoder is used.
> 
> Just to clarify, it does actually cause BUG_ON() panics, so if the
> original change is already present in a stable kernel, this fix should
> be merged to stable as well.

Pulled by Linus in 6.9 it seems, I will CC stable.

Nicolas

commit 9875c0beb8adaab602572b983fb59dbd761d5882
Merge: fe5b5ef836c8 d353c3c34af0
Author: Linus Torvalds <torvalds@...ux-foundation.org>
Date:   Wed Apr 10 13:38:35 2024 -0700

    Merge tag 'media/v6.9-2' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
    
    Pull media fixes from Mauro Carvalho Chehab:
    
     - some fixes for mediatec vcodec encoder/decoder oopses
    
    * tag 'media/v6.9-2' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media:
      media: mediatek: vcodec: support 36 bits physical address
      media: mediatek: vcodec: adding lock to protect encoder context list
      media: mediatek: vcodec: adding lock to protect decoder context list
      media: mediatek: vcodec: Fix oops when HEVC init fails
      media: mediatek: vcodec: Handle VP9 superframe bitstream with 8 sub-frames



> 
> Best,
> Tomasz

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