[PATCH 6/6] forcedeth: Fix a race during rmmod of forcedeth

From: David Decotigny
Date: Wed May 18 2011 - 20:15:27 EST

From: Salman Qazi <sqazi@xxxxxxxxxx>

The race was between del_timer_sync and nv_do_stats_poll called through
nv_get_ethtool_stats. To prevent this, we have to introduce mutual
exclusion between nv_get_ethtool_stats and del_timer_sync. Notice
that we don't put the mutual exclusion in nv_do_stats_poll. That's
because doing so would result in a deadlock, since it is a timer
callback and hence already waited for by timer deletion.

Signed-off-by: David Decotigny <decot@xxxxxxxxxx>
drivers/net/forcedeth.c | 11 ++++++++++-
1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/drivers/net/forcedeth.c b/drivers/net/forcedeth.c
index 2712ddc..2121cea 100644
--- a/drivers/net/forcedeth.c
+++ b/drivers/net/forcedeth.c
@@ -3921,6 +3921,10 @@ static void nv_poll_controller(struct net_device *dev)

+/* No locking is needed as long as this is in the timer
+ * callback. However, any other callers must call this
+ * function with np->lock held.
+ */
static void nv_do_stats_poll(unsigned long data)
struct net_device *dev = (struct net_device *) data;
@@ -4553,12 +4557,17 @@ static int nv_get_sset_count(struct net_device *dev, int sset)

static void nv_get_ethtool_stats(struct net_device *dev, struct ethtool_stats *estats, u64 *buffer)
+ unsigned long flags;
struct fe_priv *np = netdev_priv(dev);

+ spin_lock_irqsave(&np->lock, flags);
/* update stats */
nv_do_stats_poll((unsigned long)dev);

memcpy(buffer, &np->estats, nv_get_sset_count(dev, ETH_SS_STATS)*sizeof(u64));
+ spin_unlock_irqrestore(&np->lock, flags);

static int nv_link_test(struct net_device *dev)
@@ -5176,13 +5185,13 @@ static int nv_close(struct net_device *dev)

np->in_shutdown = 1;
+ del_timer_sync(&np->stats_poll);

- del_timer_sync(&np->stats_poll);


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