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Message-ID: <bc09cdb8-f349-0eae-8624-457d85d768d4@deltatee.com>
Date: Thu, 27 Jul 2023 09:31:12 -0600
From: Logan Gunthorpe <logang@...tatee.com>
To: Chengfeng Ye <dg573847474@...il.com>
Cc: Christophe JAILLET <christophe.jaillet@...adoo.fr>,
vkoul@...nel.org, Yunbo Yu <yuyunbo519@...il.com>,
dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: plx_dma: Fix potential deadlock on
&plxdev->ring_lock
On 7/27/23 00:48, Chengfeng Ye wrote:
> Hi Logan and Christophe,
>
> Thanks much for the reply and reminder, and yes, spin_lock_bh() should
> be better.
>
> When I wrote the patch I thought the spin_lock_bh() cannot be nested,
> and afraid that if some outside callers called .dma_tx_status() callback
> with softirq already disable, then spin_unlock_bh() would unintentionally
> re-enable softirq(). spin_lock_irqsave() is always safer in general thus I
> used it.
>
> But I just check the document [1] about these API and found that _bh()
> can be nested. Then use spin_lock_bh() should be better due to
> performance concern.
>
>
>> So perhaps we should just revert 1d05a0bdb420?
> Then for this one I think revert 1d05a0bdb420 should be enough. May I
> ask to revert that patch, should I do anything further? (like sending
> a new patch).
Yes, I think you can just send a revert patch explaining the reasoning
further in a commit message.
Thanks,
Logan
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