linux-kernel - Re: [PATCHv2] dma-debug: don't call __dma_entry_alloc_check_leak() under free_entries

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Message-ID: <ecf738a3-e8e5-85ac-c435-d4aa0e320b17@arm.com>
Date:   Thu, 24 Aug 2023 15:13:25 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Rob Clark <robdclark@...omium.org>, Petr Mladek <pmladek@...e.com>,
        John Ogness <john.ogness@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2] dma-debug: don't call __dma_entry_alloc_check_leak()
 under free_entries_lock

On 24/08/2023 4:15 am, Sergey Senozhatsky wrote:
> On (23/08/16 11:32), Sergey Senozhatsky wrote:
>> __dma_entry_alloc_check_leak() calls into printk -> serial console
>> output (qcom geni) and grabs port->lock under free_entries_lock
>> spin lock, which is a reverse locking dependency chain as qcom_geni
>> IRQ handler can call into dma-debug code and grab free_entries_lock
>> under port->lock.
>>
>> Move __dma_entry_alloc_check_leak() call out of free_entries_lock
>> scope so that we don't acquire serial console's port->lock under it.
> 
> Hello folks,
> 
> Have you got a chance to take a look at the patch?

[ For some reason Microsoft seem convinced all your emails are spam, so 
I have to keep digging them out of quarantine :( ]

The patch itself looks reasonable enough to me, thanks for respinning.

Acked-by: Robin Murphy <robin.murphy@....com>