Patchwork net: allow netif_carrier to be called safely from IRQ

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Submitter stephen hemminger
Date July 22, 2011, 10:53 p.m.
Message ID <20110722155356.5911225f@nehalam.ftrdhcpuser.net>
Download mbox | patch
Permalink /patch/106398/
State Accepted
Delegated to: David Miller
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Comments

stephen hemminger - July 22, 2011, 10:53 p.m.
As reported by Ben Greer and Froncois Romieu. The code path in 
the netif_carrier code leads it to try and disable
a late workqueue to reenable it immediately
netif_carrier_on
-> linkwatch_fire_event
   -> linkwatch_schedule_work
      -> cancel_delayed_work
         -> del_timer_sync  

If __cancel_delayed_work is used instead then there is no
problem of waiting for running linkwatch_event.

There is a race between linkwatch_event running re-scheduling
but it is harmless to schedule an extra scan of the linkwatch queue.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>



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David Miller - July 23, 2011, 12:16 a.m.
From: Stephen Hemminger <shemminger@vyatta.com>
Date: Fri, 22 Jul 2011 15:53:56 -0700

> As reported by Ben Greer and Froncois Romieu. The code path in 
> the netif_carrier code leads it to try and disable
> a late workqueue to reenable it immediately
> netif_carrier_on
> -> linkwatch_fire_event
>    -> linkwatch_schedule_work
>       -> cancel_delayed_work
>          -> del_timer_sync  
> 
> If __cancel_delayed_work is used instead then there is no
> problem of waiting for running linkwatch_event.
> 
> There is a race between linkwatch_event running re-scheduling
> but it is harmless to schedule an extra scan of the linkwatch queue.
> 
> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

Applied.
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Patch

--- a/net/core/link_watch.c	2011-07-22 15:25:31.027533604 -0700
+++ b/net/core/link_watch.c	2011-07-22 15:31:27.531520028 -0700
@@ -126,7 +126,7 @@  static void linkwatch_schedule_work(int
 		return;
 
 	/* It's already running which is good enough. */
-	if (!cancel_delayed_work(&linkwatch_work))
+	if (!__cancel_delayed_work(&linkwatch_work))
 		return;
 
 	/* Otherwise we reschedule it again for immediate execution. */