From: Sebastian Andrzej Siewior bigeasy@linutronix.de
[ Upstream commit 3f8ae9fe0409698799e173f698b714f34570b64b ]
xrs700x_read_port_counters() updates the stats from a worker using the u64_stats_update_begin() version. This is okay on 32-UP since on the reader side preemption is disabled. On 32bit-SMP the writer can be preempted by the reader at which point the reader will spin on the seqcount until writer continues and completes the update.
Assigning the mib_mutex mutex to the underlying seqcount would ensure proper synchronisation. The API for that on the u64_stats_init() side isn't available. Since it is the only user, just use disable interrupts during the update.
Use u64_stats_update_begin_irqsave() on the writer side to ensure an uninterrupted update.
Fixes: ee00b24f32eb8 ("net: dsa: add Arrow SpeedChips XRS700x driver") Cc: Andrew Lunn andrew@lunn.ch Cc: Florian Fainelli f.fainelli@gmail.com Cc: George McCollister george.mccollister@gmail.com Cc: Vivien Didelot vivien.didelot@gmail.com Cc: Vladimir Oltean olteanv@gmail.com Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de Acked-by: George McCollister george.mccollister@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/dsa/xrs700x/xrs700x.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/net/dsa/xrs700x/xrs700x.c b/drivers/net/dsa/xrs700x/xrs700x.c index 469420941054e..cf363d5a30020 100644 --- a/drivers/net/dsa/xrs700x/xrs700x.c +++ b/drivers/net/dsa/xrs700x/xrs700x.c @@ -108,6 +108,7 @@ static void xrs700x_read_port_counters(struct xrs700x *priv, int port) { struct xrs700x_port *p = &priv->ports[port]; struct rtnl_link_stats64 stats; + unsigned long flags; int i;
memset(&stats, 0, sizeof(stats)); @@ -137,9 +138,9 @@ static void xrs700x_read_port_counters(struct xrs700x *priv, int port) */ stats.rx_packets += stats.multicast;
- u64_stats_update_begin(&p->syncp); + flags = u64_stats_update_begin_irqsave(&p->syncp); p->stats64 = stats; - u64_stats_update_end(&p->syncp); + u64_stats_update_end_irqrestore(&p->syncp, flags);
mutex_unlock(&p->mib_mutex); }