linux-kernel - Re: [PATCH v2 1/2] atm: solos-pci: Fix potential deadlock on &cli_queue

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Message-ID: <20231006162835.79484017@kernel.org>
Date:   Fri, 6 Oct 2023 16:28:35 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Chengfeng Ye <dg573847474@...il.com>
Cc:     3chas3@...il.com, davem@...emloft.net, horms@...nel.org,
        linux-atm-general@...ts.sourceforge.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] atm: solos-pci: Fix potential deadlock on
 &cli_queue_lock

On Thu,  5 Oct 2023 07:48:58 +0000 Chengfeng Ye wrote:
> As &card->cli_queue_lock is acquired under softirq context along the

you say softirq here

> following call chain from solos_bh(), other acquisition of the same
> lock inside process context should disable at least bh to avoid double
> lock.
> 
> <deadlock #1>
> console_show()
> --> spin_lock(&card->cli_queue_lock)  
> <interrupt>
>    --> solos_bh()
>    --> spin_lock(&card->cli_queue_lock)  
> 
> This flaw was found by an experimental static analysis tool I am
> developing for irq-related deadlock.
> 
> To prevent the potential deadlock, the patch uses spin_lock_irqsave()
> on the card->cli_queue_lock under process context code consistently
> to prevent the possible deadlock scenario.

and irqsave here. I think you're right that it's just softirq (== bh)
that may deadlock, so no need to take the irqsave() version in process
context.
-- 
pw-bot: cr