Re: [BUG] 2.6.21 hang in cancel_rearming_delayed_workqueue()

[Jason Wessel <jason.wessel@windriver.com>]

Jarek Poplawski wrote:
> On 25-05-2007 05:21, Jason Wessel wrote:
>   
> > There is a problem with the calling cancel_rearming_delayed_work if the 
> > timer was not yet active.
> >
> >
> > It is possible that the problem exists else where, but I thought I would 
> > ask if this is expected?
> >
> >     
>
>
> " * cancel_rearming_delayed_workqueue - reliably kill off a delayed
>  work whose handler rearms the delayed work."
>
> So, it cannot be used in netpoll_cleanup() if there is no rearming
> during this cancel at all. This is a tricky behaviour of course,
> and is changed in 2.6.22-rc.
>
>   

I had read that as well.  It seems this the API for the cancel is 
restricted such that you cannot call it if there is nothing to cancel.

This means the netpoll code is incorrect and the simple fix is 
attached.  With the change the netpoll_cleanup works correctly in 2.6.21.

Thanks,
Jason.

Do not call cancel_rearming_delayed_work() if there is no
pending work.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

---
 net/core/netpoll.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Index: linux-2.6.21/net/core/netpoll.c
===================================================================
--- linux-2.6.21.orig/net/core/netpoll.c
+++ linux-2.6.21/net/core/netpoll.c
@@ -781,8 +781,10 @@ void netpoll_cleanup(struct netpoll *np)
 			if (atomic_dec_and_test(&npinfo->refcnt)) {
 				skb_queue_purge(&npinfo->arp_tx);
 				skb_queue_purge(&npinfo->txq);
-				cancel_rearming_delayed_work(&npinfo->tx_work);
-				flush_scheduled_work();
+				if (delayed_work_pending(&npinfo->tx_work)) {
+					cancel_rearming_delayed_work(&npinfo->tx_work);
+					flush_scheduled_work();
+				}
 
 				kfree(npinfo);
 			}