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Date:   Thu, 27 Jul 2023 09:31:12 -0600
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To:     Chengfeng Ye <dg573847474@gmail.com>
Cc:     Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
        vkoul@kernel.org, Yunbo Yu <yuyunbo519@gmail.com>,
        dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org
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From:   Logan Gunthorpe <logang@deltatee.com>
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Subject: Re: [PATCH] dmaengine: plx_dma: Fix potential deadlock on
 &plxdev->ring_lock
Precedence: bulk


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