[PATCH net] ice: use READ_ONCE() to access cached PHC time

[Aleksandr Loktionov <aleksandr.loktionov@intel.com>]

From: Sergey Temerkhanov <sergey.temerkhanov@intel.com>

ptp.cached_phc_time is a 64-bit value updated by a periodic work item
on one CPU and read locklessly on another.  On 32-bit or non-atomic
architectures this can result in a torn read.  Use READ_ONCE() to
enforce a single atomic load.

Fixes: 77a781155a65 ("ice: enable receive hardware timestamping")
Cc: stable@vger.kernel.org
Signed-off-by: Sergey Temerkhanov <sergey.temerkhanov@intel.com>
Signed-off-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
---

 drivers/net/ethernet/intel/ice/ice_ptp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_ptp.c b/drivers/net/ethernet/intel/ice/ice_ptp.c
index 8b0530b..2ea4dbc 100644
--- a/drivers/net/ethernet/intel/ice/ice_ptp.c
+++ b/drivers/net/ethernet/intel/ice/ice_ptp.c
@@ -350,7 +350,7 @@ static u64 ice_ptp_extend_40b_ts(struct ice_pf *pf, u64 in_tstamp)
 		return 0;
 	}
 
-	return ice_ptp_extend_32b_ts(pf->ptp.cached_phc_time,
+	return ice_ptp_extend_32b_ts(READ_ONCE(pf->ptp.cached_phc_time),
 				     (in_tstamp >> 8) & mask);
 }
 
-- 
2.52.0