linux-kernel - Re: [PATCH] dma-fence: allow dma fence to have their own lock

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Message-ID: <YpWCvniLzJfcp684@google.com>
Date:   Tue, 31 May 2022 11:51:42 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Christian König <christian.koenig@....com>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Tomasz Figa <tfiga@...omium.org>,
        Ricardo Ribalda <ribalda@...omium.org>,
        Christoph Hellwig <hch@...radead.org>,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dma-fence: allow dma fence to have their own lock

On (22/05/30 16:55), Christian König wrote:
> Am 30.05.22 um 16:22 schrieb Sergey Senozhatsky:
> > [SNIP]
> > So the `lock` should have at least same lifespan as the DMA fence
> > that borrows it, which is impossible to guarantee in our case.
> 
> Nope, that's not correct. The lock should have at least same lifespan as the
> context of the DMA fence.

How does one know when it's safe to release the context? DMA fence
objects are still transparently refcount-ed and "live their own lives",
how does one synchronize lifespans?