netdev - [PATCH] Re: [NETPOLL] netconsole: fix soft lockup when removing module

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Message-ID: <20070702075226.GB1639@ff.dom.local>
Date:	Mon, 2 Jul 2007 09:52:26 +0200
From:	Jarek Poplawski <jarkao2@...pl>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"David S\. Miller" <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH] Re: [NETPOLL] netconsole: fix soft lockup when removing module


>From my recent patch:

> >    #1
> >    Until kernel ver. 2.6.21 (including) cancel_rearming_delayed_work()
> >    required a work function should always (unconditionally) rearm with
> >    delay > 0 - otherwise it would endlessly loop. This patch replaces
> >    this function with cancel_delayed_work(). Later kernel versions don't
> >    require this, so here it's only for uniformity.

But Oleg Nesterov <oleg@...sign.ru> found:

> But 2.6.22 doesn't need this change, why it was merged?
> 
> In fact, I suspect this change adds a race,
...

His description was right (thanks), so this patch reverts #1.

Signed-off-by: Jarek Poplawski <jarkao2@...pl>

---

diff -Nurp 2.6.22-rc7-/net/core/netpoll.c 2.6.22-rc7/net/core/netpoll.c
--- 2.6.22-rc7-/net/core/netpoll.c	2007-07-02 09:03:27.000000000 +0200
+++ 2.6.22-rc7/net/core/netpoll.c	2007-07-02 09:32:34.000000000 +0200
@@ -72,8 +72,7 @@ static void queue_process(struct work_st
 			netif_tx_unlock(dev);
 			local_irq_restore(flags);
 
-			if (atomic_read(&npinfo->refcnt))
-				schedule_delayed_work(&npinfo->tx_work, HZ/10);
+			schedule_delayed_work(&npinfo->tx_work, HZ/10);
 			return;
 		}
 		netif_tx_unlock(dev);
@@ -786,7 +785,7 @@ 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_delayed_work(&npinfo->tx_work);
+				cancel_rearming_delayed_work(&npinfo->tx_work);
 				flush_scheduled_work();
 
 				/* clean after last, unfinished work */
-
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