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From: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
To: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>,
	Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Matthieu Baerts <matthieu.baerts@tessares.net>,
	Stefan Schmidt <stefan@datenfreihafen.org>,
	linux-bluetooth <linux-bluetooth@vger.kernel.org>,
	"open list:NETWORKING [GENERAL]" <netdev@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>,
	skhan@linuxfoundation.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-kernel-mentees@lists.linuxfoundation.org
Subject: Re: [PATCH v3 2/2] Bluetooth: fix inconsistent lock state in rfcomm_connect_ind
Date: Fri, 30 Jul 2021 17:06:09 +0800	[thread overview]
Message-ID: <40f38642-faa9-8c63-4306-6477e272cfbe@gmail.com> (raw)
In-Reply-To: <06E57598-5723-459D-9CE3-4DD8D3145D86@holtmann.org>

Hi Marcel,

On 30/7/21 3:53 am, Marcel Holtmann wrote:
> Hi Desmond,
> 
>> Commit fad003b6c8e3d ("Bluetooth: Fix inconsistent lock state with
>> RFCOMM") fixed a lockdep warning due to sk->sk_lock.slock being
>> acquired without disabling softirq while the lock is also used in
>> softirq context. This was done by disabling interrupts before calling
>> bh_lock_sock in rfcomm_sk_state_change.
>>
>> Later, this was changed in commit e6da0edc24ee ("Bluetooth: Acquire
>> sk_lock.slock without disabling interrupts") to disable softirqs
>> only.
>>
>> However, there is another instance of sk->sk_lock.slock being acquired
>> without disabling softirq in rfcomm_connect_ind. This patch fixes this
>> by disabling local bh before the call to bh_lock_sock.
> 
> back in the days, the packet processing was done in a tasklet, but these days it is done in a workqueue. So shouldn’t this be just converted into a lock_sock(). Am I missing something?
> 

Thanks for the info. I think you're right, I just didn't understand very 
much when I wrote this patch.

If I'm understanding correctly, it seems that both the bh_lock_sock in 
rfcomm_connect_ind, and spin_lock_bh in rfcomm_sk_state_change need to 
be changed to lock_sock, otherwise they don't provide any 
synchronization with other functions in RFCOMM that use lock_sock.

If that sounds correct I can prepare the patch for that.

Best wishes,
Desmond

  reply	other threads:[~2021-07-30  9:06 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-21  9:38 [PATCH v3 0/2] Bluetooth: fix inconsistent lock states Desmond Cheong Zhi Xi
2021-07-21  9:38 ` [PATCH v3 1/2] Bluetooth: fix inconsistent lock state in SCO Desmond Cheong Zhi Xi
2021-07-21 11:09   ` Bluetooth: fix inconsistent lock states bluez.test.bot
2021-07-27  0:30   ` [PATCH v3 1/2] Bluetooth: fix inconsistent lock state in SCO Luiz Augusto von Dentz
2021-07-27  5:13     ` Desmond Cheong Zhi Xi
2021-07-21  9:38 ` [PATCH v3 2/2] Bluetooth: fix inconsistent lock state in rfcomm_connect_ind Desmond Cheong Zhi Xi
2021-07-29 19:53   ` Marcel Holtmann
2021-07-30  9:06     ` Desmond Cheong Zhi Xi [this message]
2021-07-30 13:40       ` Marcel Holtmann

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