From 5c8e98fe4742734c1c6b81699a86d1f5b03841e0 Mon Sep 17 00:00:00 2001
From: Linas Vepstas <linas@austin.ibm.com>
Date: Tue, 20 Feb 2007 16:41:59 -0600
Subject: [PATCH] spidernet: transmit race

Multiple threads performing a transmit can race into
the spidernet tx ring cleanup code. This puts the
relevant check under a lock.

Signed-off-by: Linas Vepstas <lins@austin.ibm.com>
Cc: Jens Osterkamp <Jens.Osterkamp@de.ibm.com>
Cc: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
---
 drivers/net/spider_net.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/spider_net.c b/drivers/net/spider_net.c
index 15b0bcaec467..653a91adacc7 100644
--- a/drivers/net/spider_net.c
+++ b/drivers/net/spider_net.c
@@ -803,8 +803,12 @@ spider_net_release_tx_chain(struct spider_net_card *card, int brutal)
 	unsigned long flags;
 	int status;
 
-	while (chain->tail != chain->head) {
+	while (1) {
 		spin_lock_irqsave(&chain->lock, flags);
+		if (chain->tail == chain->head) {
+			spin_unlock_irqrestore(&chain->lock, flags);
+			return 0;
+		}
 		descr = chain->tail;
 		hwdescr = descr->hwdescr;