From: Dave Young <hidave.darkstar@gmail.com>
Date: Mon, 2 Jun 2008 06:50:52 +0000 (-0700)
Subject: bluetooth: rfcomm_dev_state_change deadlock fix
X-Git-Tag: v2.6.26-rc5~1^2~29
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=537d59af73d894750cff14f90fe2b6d77fbab15b;p=pandora-kernel.git

bluetooth: rfcomm_dev_state_change deadlock fix

There's logic in __rfcomm_dlc_close:
	rfcomm_dlc_lock(d);
	d->state = BT_CLOSED;
	d->state_changed(d, err);
	rfcomm_dlc_unlock(d);

In rfcomm_dev_state_change, it's possible that rfcomm_dev_put try to
take the dlc lock, then we will deadlock.

Here fixed it by unlock dlc before rfcomm_dev_get in
rfcomm_dev_state_change.

why not unlock just before rfcomm_dev_put? it's because there's
another problem.  rfcomm_dev_get/rfcomm_dev_del will take
rfcomm_dev_lock, but in rfcomm_dev_add the lock order is :
rfcomm_dev_lock --> dlc lock

so I unlock dlc before the taken of rfcomm_dev_lock.

Actually it's a regression caused by commit
1905f6c736cb618e07eca0c96e60e3c024023428 ("bluetooth :
__rfcomm_dlc_close lock fix"), the dlc state_change could be two
callbacks : rfcomm_sk_state_change and rfcomm_dev_state_change. I
missed the rfcomm_sk_state_change that time.

Thanks Arjan van de Ven <arjan@linux.intel.com> for the effort in
commit 4c8411f8c115def968820a4df6658ccfd55d7f1a ("bluetooth: fix
locking bug in the rfcomm socket cleanup handling") but he missed the
rfcomm_dev_state_change lock issue.

Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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