[PATCH AUTOSEL 5.7 093/388] net: mdiobus: Disable preemption upon u64_stats update

Sasha Levin
2020-06-18T02:47:58Z

From: "Ahmed S. Darwish" <a.darwish@linutronix.de>

[ 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>
---
drivers/net/phy/mdio_bus.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 7a4eb3f2cb74..a1a4dee2a033 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();
}

/**
--
2.25.1