linux-kernel - Re: [PATCH] bluetooth: fix locking in hci_sock_dev

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Date:	Wed, 16 May 2007 22:51:29 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	ssatyam@....iitk.ac.in
Cc:	akpm@...ux-foundation.org, marcel@...tmann.org, jikos@...os.cz,
	gregkh@...e.de, jeremy@...p.org, maxk@...lcomm.com, clg@...ibm.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bluetooth: fix locking in hci_sock_dev_event()

From: Satyam Sharma <ssatyam@....iitk.ac.in>
Date: Thu, 17 May 2007 11:13:36 +0530 (IST)

> [PATCH] bluetooth: fix locking in hci_sock_dev_event()
> 
> We presently use lock_sock() to acquire a lock on a socket in
> hci_sock_dev_event(), but this goes BUG because lock_sock()
> can sleep and we're already holding a read-write spinlock at
> that point. So, we must use the non-sleeping BH version,
> bh_lock_sock().
> 
> However, hci_sock_dev_event() is called from user context and
> hence using simply bh_lock_sock() will deadlock against a
> concurrent softirq that tries to acquire a lock on the same
> socket. Hence, disabling BH's before acquiring the socket lock
> and enable them afterwards, is the proper solution to fix
> socket locking in hci_sock_dev_event().
> 
> Cc: David Miller <davem@...emloft.net>
> Signed-off-by: Satyam Sharma <ssatyam@....iitk.ac.in>
> Signed-off-by: Marcel Holtmann <marcel@...tmann.org>
> Signed-off-by: Jiri Kosina <jkosina@...e.cz>

Thanks I'll merge this in.
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