On Thu, 5 Apr 2007, Guennadi Liakhovetski wrote:
> Ok, a simple analysis reveals the recursive spinlock:
>
> On Thu, 5 Apr 2007, Guennadi Liakhovetski wrote:
>
> > [<bf12b220>] (ppp_channel_push+0x0/0xc8 [ppp_generic]) from [<bf12bf98>] (ppp_output_wakeup+0x18/0x1c [ppp_generic])
> ===> ^^^^^^^^^^^^^^^^
> > r7 = C38F42BC r6 = C38F4200 r5 = C38F4200 r4 = 00000000
>
> ===> spin_lock_bh(&pch->downl);
>
> > [<bf12bf80>] (ppp_output_wakeup+0x0/0x1c [ppp_generic]) from [<bf132c98>] (irnet_flow_indication+0x38/0x3c [irnet])
> > [<bf132c60>] (irnet_flow_indication+0x0/0x3c [irnet]) from [<bf104e4c>] (irttp_run_tx_queue+0x1c0/0x1d4 [irda])
> > [<bf104c8c>] (irttp_run_tx_queue+0x0/0x1d4 [irda]) from [<bf104f88>] (irttp_data_request+0x128/0x4f8 [irda])
> > r8 = BF121560 r7 = 00000002 r6 = C38F4200 r5 = C21418B8
> > r4 = C21418B8
> > [<bf104e60>] (irttp_data_request+0x0/0x4f8 [irda]) from [<bf1321bc>] (ppp_irnet_send+0x134/0x238 [irnet])
> > [<bf132088>] (ppp_irnet_send+0x0/0x238 [irnet]) from [<bf12a600>] (ppp_push+0x80/0xb8 [ppp_generic])
> > r7 = C3A436E0 r6 = 00000000 r5 = C21418B8 r4 = C1489600
> > [<bf12a580>] (ppp_push+0x0/0xb8 [ppp_generic]) from [<bf12a8d8>] (ppp_xmit_process+0x34/0x50c [ppp_generic])
> ===> ^^^^^^^^
> > r7 = 00000021 r6 = C21418B8 r5 = C1489600 r4 = 00000000
>
> ===> spin_lock_bh(&pch->downl);
For comments, below is a patch I am testing ATM. It doesn't look right nor
very pretty, but I couldn't come up with anything better. I do sign-off
for it in case nothing better is proposed and it is decided to push it for
2.6.21.
Thanks
Guennadi
---------------------------------
Guennadi Liakhovetski, Ph.D.
DSA Daten- und Systemtechnik GmbH
Pascalstr. 28
D-52076 Aachen
Germany
Fix recursion with PPP over IrNET.
Signed-off-by: G. Liakhovetski <gl@xxxxxxxxx>
diff -u -r1.1.1.19.4.1 ppp_generic.c
--- a/drivers/net/ppp_generic.c 26 Mar 2007 09:21:32 -0000 1.1.1.19.4.1
+++ b/drivers/net/ppp_generic.c 5 Apr 2007 15:01:45 -0000
@@ -155,6 +155,7 @@
struct ppp_channel *chan; /* public channel data structure */
struct rw_semaphore chan_sem; /* protects `chan' during chan ioctl */
spinlock_t downl; /* protects `chan', file.xq dequeue */
+ struct task_struct *locker; /* owner of the downl lock */
struct ppp *ppp; /* ppp unit we're connected to */
struct list_head clist; /* link in list of channels per unit */
rwlock_t upl; /* protects `ppp' */
@@ -1214,8 +1215,11 @@
spin_lock_bh(&pch->downl);
if (pch->chan) {
+ /* Prevent recursive locking */
+ pch->locker = current;
if (pch->chan->ops->start_xmit(pch->chan, skb))
ppp->xmit_pending = NULL;
+ pch->locker = NULL;
} else {
/* channel got unregistered */
kfree_skb(skb);
@@ -1435,6 +1439,9 @@
struct sk_buff *skb;
struct ppp *ppp;
+ if (pch->locker == current)
+ return;
+
spin_lock_bh(&pch->downl);
if (pch->chan != 0) {
while (!skb_queue_empty(&pch->file.xq)) {
-
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