linux-kernel - Re: [PATCH net v1] net: wan: fsl_qmc_hdlc: Convert carrier

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Message-ID: <20240731084551.GM1967603@kernel.org>
Date: Wed, 31 Jul 2024 09:45:51 +0100
From: Simon Horman <horms@...nel.org>
To: Herve Codina <herve.codina@...tlin.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	netdev@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	stable@...r.kernel.org
Subject: Re: [PATCH net v1] net: wan: fsl_qmc_hdlc: Convert carrier_lock
 spinlock to a mutex

On Tue, Jul 30, 2024 at 08:31:04AM +0200, Herve Codina wrote:
> The carrier_lock spinlock protects the carrier detection. While it is
> hold, framer_get_status() is called witch in turn takes a mutex.
> This is not correct and can lead to a deadlock.
> 
> A run with PROVE_LOCKING enabled detected the issue:
>   [ BUG: Invalid wait context ]
>   ...
>   c204ddbc (&framer->mutex){+.+.}-{3:3}, at: framer_get_status+0x40/0x78
>   other info that might help us debug this:
>   context-{4:4}
>   2 locks held by ifconfig/146:
>   #0: c0926a38 (rtnl_mutex){+.+.}-{3:3}, at: devinet_ioctl+0x12c/0x664
>   #1: c2006a40 (&qmc_hdlc->carrier_lock){....}-{2:2}, at: qmc_hdlc_framer_set_carrier+0x30/0x98
> 
> Avoid the spinlock usage and convert carrier_lock to a mutex.
> 
> Fixes: 54762918ca85 ("net: wan: fsl_qmc_hdlc: Add framer support")
> Cc: stable@...r.kernel.org
> Signed-off-by: Herve Codina <herve.codina@...tlin.com>

Reviewed-by: Simon Horman <horms@...nel.org>