linux-kernel - Re: [PATCH v2] dmaengine: plx_dma: Fix potential deadlock on &plxdev->ring

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Message-ID: <CAAo+4rWW67VSpdwo_dstqAb-FiKeoK3YmaNgiX7vXBerqEWBkA@mail.gmail.com>
Date:   Tue, 29 Aug 2023 11:10:27 +0800
From:   Chengfeng Ye <dg573847474@...il.com>
To:     Eric Schwarz <eas@...optimization.com>
Cc:     dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        christophe.jaillet@...adoo.fr, vkoul@...nel.org,
        logang@...tatee.com
Subject: Re: [PATCH v2] dmaengine: plx_dma: Fix potential deadlock on &plxdev->ring_lock

Hi Eric,

Thank you for your interest in it.

For a dynamic detection solution, then the answer is yes.
Lockdep, which should be enabled by CONFIG_DEBUG_SPINLOCK,
has the ability to detect such deadlocks. But the problem is that the detection
requires input and exact thread interleaving to trigger the bug, otherwise
the bugs would be buried and cannot be detected.

For static analysis, I think the answer is no. Smatch, like other
static deadlock detection algorithms in CBMC[1] and Infer[2], should be
designed to reason thread interaction but not interrupts, which requires
new algorithms that I am working on.

Besides, may I ask a question that I have sent some patches[3][4] weeks
ago, but have not yet got a reply. Would reviewers check the patches
later or should I ping them again?

[1] http://www.cprover.org/deadlock-detection/
[2] https://github.com/facebook/infer
[3] https://lore.kernel.org/lkml/20230726062313.77121-1-dg573847474@gmail.com/
[4] https://lore.kernel.org/lkml/20230726051727.64088-1-dg573847474@gmail.com/

Thanks,
Chengfeng