From: Ahmed S. Darwish <a.darwish@linutronix.de>
Date: Wed, 3 Jun 2020 14:49:47 +0000 (+0200)
Subject: net: mdiobus: Disable preemption upon u64_stats update
X-Git-Tag: v5.7.6~383
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=aeadf66a5db6de978dc94f99b8a10c0c34f05a48;p=users%2Fdwmw2%2Flinux.git

net: mdiobus: Disable preemption upon u64_stats update

[ Upstream commit c7e261d81783387a0502878cd229327e7c54322e ]

The u64_stats mechanism uses sequence counters to protect against 64-bit
values tearing on 32-bit architectures. Updating u64_stats is thus a
sequence counter write side critical section where preemption must be
disabled.

For mdiobus_stats_acct(), disable preemption upon the u64_stats update.
It is called from process context through mdiobus_read() and
mdiobus_write().

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 7a4eb3f2cb743..a1a4dee2a033a 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -757,6 +757,7 @@ EXPORT_SYMBOL(mdiobus_scan);
 
 static void mdiobus_stats_acct(struct mdio_bus_stats *stats, bool op, int ret)
 {
+	preempt_disable();
 	u64_stats_update_begin(&stats->syncp);
 
 	u64_stats_inc(&stats->transfers);
@@ -771,6 +772,7 @@ static void mdiobus_stats_acct(struct mdio_bus_stats *stats, bool op, int ret)
 		u64_stats_inc(&stats->writes);
 out:
 	u64_stats_update_end(&stats->syncp);
+	preempt_enable();
 }
 
 /**