Merge remote-tracking branch 'torvalds/master' into perf/core

To pick up fixes from perf/urgent that recently got merged.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 7b288a121a41..d5dc6be2522c 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -283,13 +283,17 @@ static void trace_napi_poll_hit(void *ignore, struct napi_struct *napi,
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(new_stat, &hw_stats_list, list) {
+		struct net_device *dev;
+
 		/*
 		 * only add a note to our monitor buffer if:
 		 * 1) this is the dev we received on
 		 * 2) its after the last_rx delta
 		 * 3) our rx_dropped count has gone up
 		 */
-		if ((new_stat->dev == napi->dev)  &&
+		/* Paired with WRITE_ONCE() in dropmon_net_event() */
+		dev = READ_ONCE(new_stat->dev);
+		if ((dev == napi->dev)  &&
 		    (time_after(jiffies, new_stat->last_rx + dm_hw_check_delta)) &&
 		    (napi->dev->stats.rx_dropped != new_stat->last_drop_val)) {
 			trace_drop_common(NULL, NULL);
@@ -1576,7 +1580,10 @@ static int dropmon_net_event(struct notifier_block *ev_block,
 		mutex_lock(&net_dm_mutex);
 		list_for_each_entry_safe(new_stat, tmp, &hw_stats_list, list) {
 			if (new_stat->dev == dev) {
-				new_stat->dev = NULL;
+
+				/* Paired with READ_ONCE() in trace_napi_poll_hit() */
+				WRITE_ONCE(new_stat->dev, NULL);
+
 				if (trace_state == TRACE_OFF) {
 					list_del_rcu(&new_stat->list);
 					kfree_rcu(new_stat, rcu);