linux-kernel - Re: [PATCHv2] media: venc: destroy hfi session after m2m

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Message-ID: <1153ebfe-eb98-4b8c-8fd4-914e7a3e063b@linaro.org>
Date: Thu, 19 Dec 2024 14:03:08 +0000
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Sergey Senozhatsky <senozhatsky@...omium.org>,
 Stanimir Varbanov <stanimir.k.varbanov@...il.com>,
 Vikash Garodia <quic_vgarodia@...cinc.com>
Cc: Hans Verkuil <hverkuil@...all.nl>, linux-media@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCHv2] media: venc: destroy hfi session after m2m_ctx release

On 19/12/2024 05:37, Sergey Senozhatsky wrote:
> This partially reverts commit that made hfi_session_destroy()
> the first step of vdec/venc close().  The reason being is a
> regression report when, supposedly, encode/decoder is closed
> with still active streaming (no ->stop_streaming() call before
> close()) and pending pkts, so isr_thread cannot find instance
> and fails to process those pending pkts.  This was the idea
> behind the original patch - make it impossible to use instance
> under destruction, because this is racy, but apparently there
> are uses cases that depend on that unsafe pattern.  Return to
> the old (unsafe) behaviour for the time being (until a better
> fix is found).
> 
> Fixes: 45b1a1b348ec ("media: venus: sync with threaded IRQ during inst destruction")
> Cc: stable@...r.kernel.org
> Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> ---
>   drivers/media/platform/qcom/venus/core.c | 8 ++------
>   1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/platform/qcom/venus/core.c b/drivers/media/platform/qcom/venus/core.c
> index 2d27c5167246..807487a1f536 100644
> --- a/drivers/media/platform/qcom/venus/core.c
> +++ b/drivers/media/platform/qcom/venus/core.c
> @@ -506,18 +506,14 @@ static __maybe_unused int venus_runtime_suspend(struct device *dev)
>   void venus_close_common(struct venus_inst *inst)
>   {
>   	/*
> -	 * First, remove the inst from the ->instances list, so that
> -	 * to_instance() will return NULL.
> -	 */
> -	hfi_session_destroy(inst);
> -	/*
> -	 * Second, make sure we don't have IRQ/IRQ-thread currently running
> +	 * Make sure we don't have IRQ/IRQ-thread currently running
>   	 * or pending execution, which would race with the inst destruction.
>   	 */
>   	synchronize_irq(inst->core->irq);
>   
>   	v4l2_m2m_ctx_release(inst->m2m_ctx);
>   	v4l2_m2m_release(inst->m2m_dev);
> +	hfi_session_destroy(inst);
>   	v4l2_fh_del(&inst->fh);
>   	v4l2_fh_exit(&inst->fh);
>   	v4l2_ctrl_handler_free(&inst->ctrl_handler);

Two questions:

1: Will this revert re-instantiate the original bug @

commit 45b1a1b348ec178a599323f1ce7d7932aea8c6d4
Author: Sergey Senozhatsky <senozhatsky@...omium.org>
Date:   Sat Oct 26 01:56:42 2024 +0900

     media: venus: sync with threaded IRQ during inst destruction


2: Why not balanced out the ordering of calls by moving
    hfi_session_create() in vdec_open_common() ? to match
    the ordering in venus_close_common();

---
bod