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| author |   Xiaotian Feng <xtfeng@gmail.com> | 2009-10-21 23:07:04 +0000 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2009-10-22 18:27:53 -0700 |
| commit | 2bd9af046fdc10703b266b0f3b25423f0b7d703e (patch) | |
| tree | c20f3117f3cf7af8d309ff919e4afd5ba3c48184 /drivers/isdn | |
| parent | netxen: avoid undue board config check (diff) | |
| download | linux-dev-2bd9af046fdc10703b266b0f3b25423f0b7d703e.tar.xz linux-dev-2bd9af046fdc10703b266b0f3b25423f0b7d703e.zip | |
isdn: fix possible circular locking dependency
There's a circular locking dependency:
---> isdn_net_get_locked_lp
--->lock &nd->queue_lock
--->lock &nd->queue->xmit_lock
.....................
---->unlock &nd->queue_lock
---> isdn_net_writebuf_skb (called with &nd->queue->xmit_lock locked)
---->isdn_net_inc_frame_cnt
---->isdn_net_device_busy
----> lock &nd->queue_lock
This will trigger lockdep warnings:
=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.32-rc4-testing #7
-------------------------------------------------------
ipppd/28379 is trying to acquire lock:
(&netdev->queue_lock){......}, at: [<e62ad0fd>] isdn_net_device_busy+0x2c/0x74 [isdn]
but task is already holding lock:
(&netdev->local->xmit_lock){+.....}, at: [<e62aefc2>] isdn_net_write_super+0x3f/0x6e [isdn]
which lock already depends on the new lock.
.......
We don't need to lock nd->queue->xmit_lock to protect single
isdn_net_lp_busy(). This can fix above lockdep warnings.
Reported-and-tested-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: Xiaotian Feng <xtfeng@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/isdn')
| -rw-r--r-- | drivers/isdn/i4l/isdn_net.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/isdn/i4l/isdn_net.h b/drivers/isdn/i4l/isdn_net.h index 74032d0881ef..7511f08effa5 100644 --- a/drivers/isdn/i4l/isdn_net.h +++ b/drivers/isdn/i4l/isdn_net.h @@ -83,19 +83,19 @@ static __inline__ isdn_net_local * isdn_net_get_locked_lp(isdn_net_dev *nd) spin_lock_irqsave(&nd->queue_lock, flags); lp = nd->queue; /* get lp on top of queue */ - spin_lock(&nd->queue->xmit_lock); while (isdn_net_lp_busy(nd->queue)) { - spin_unlock(&nd->queue->xmit_lock); nd->queue = nd->queue->next; if (nd->queue == lp) { /* not found -- should never happen */ lp = NULL; goto errout; } - spin_lock(&nd->queue->xmit_lock); } lp = nd->queue; nd->queue = nd->queue->next; + spin_unlock_irqrestore(&nd->queue_lock, flags); + spin_lock(&lp->xmit_lock); local_bh_disable(); + return lp; errout: spin_unlock_irqrestore(&nd->queue_lock, flags); return lp; |