linux-kernel - [58/90] net: allow netif_carrier to be called safely from IRQ

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Message-Id: <20110812210557.190724106@clark.kroah.org>
Date:	Fri, 12 Aug 2011 14:04:43 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Stephen Hemminger <shemminger@...tta.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [58/90] net: allow netif_carrier to be called safely from IRQ

3.0-stable review patch.  If anyone has any objections, please let us know.

------------------


From: stephen hemminger <shemminger@...tta.com>

[ Upstream commit 1821f7cd65ad9ea56580b830ac79bf4c4fef59cb ]

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@...tta.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 net/core/link_watch.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -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. */


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