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>

1 files changed, 5 insertions, 1 deletions

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;