net: mdiobus: Disable preemption upon u64_stats update

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>

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 255fdfcc13a6c2ec3d96d71c82cc69f4aef1b191..6ceee82b2839e37d61bb1398bfd380528ffd809b 100644 (file)
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -764,6 +764,7 @@ 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);
@@ -778,6 +779,7 @@ 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();
 }
 
 /**