From d6ec2f711c945ee969be5709aa23e40ae4c57368 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Thu, 25 Aug 2022 13:36:44 +0200 Subject: [PATCH] net: dsa: xrs700x: Use irqsave variant for u64 stats update [ 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 Cc: Florian Fainelli Cc: George McCollister Cc: Vivien Didelot Cc: Vladimir Oltean Signed-off-by: Sebastian Andrzej Siewior Acked-by: George McCollister Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- 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 4694209..cf363d5 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); } -- 2.7.4