linux-kernel - Re: [PATCH] dmaengine: mediatek: Fix deadlock caused by synchronize

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Date:   Wed, 04 Oct 2023 19:48:03 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     sean.wang@...iatek.com, Duoming Zhou <duoming@....edu.cn>
Cc:     matthias.bgg@...il.com, angelogioacchino.delregno@...labora.com,
        dmaengine@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: mediatek: Fix deadlock caused by
 synchronize_irq()


On Sun, 06 Aug 2023 11:25:11 +0800, Duoming Zhou wrote:
> The synchronize_irq(c->irq) will not return until the IRQ handler
> mtk_uart_apdma_irq_handler() is completed. If the synchronize_irq()
> holds a spin_lock and waits the IRQ handler to complete, but the
> IRQ handler also needs the same spin_lock. The deadlock will happen.
> The process is shown below:
> 
>           cpu0                        cpu1
> mtk_uart_apdma_device_pause() | mtk_uart_apdma_irq_handler()
>   spin_lock_irqsave()         |
>                               |   spin_lock_irqsave()
>   //hold the lock to wait     |
>   synchronize_irq()           |
> 
> [...]

Applied, thanks!

[1/1] dmaengine: mediatek: Fix deadlock caused by synchronize_irq()
      commit: 01f1ae2733e2bb4de92fefcea5fda847d92aede1

Best regards,
-- 
~Vinod