net: add data-race annotations in softnet_seq_show()

softnet_seq_show() reads several fields that might be updated
concurrently. Add READ_ONCE() and WRITE_ONCE() annotations.

Signed-off-by: Eric Dumazet <[email protected]>
Reviewed-by: Willem de Bruijn <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: edumazet

net/core/dev.c

@@ -4953,7 +4953,8 @@ static void rps_trigger_softirq(void *data)
 	struct softnet_data *sd = data;
 
 	____napi_schedule(sd, &sd->backlog);
-	sd->received_rps++;
+	/* Pairs with READ_ONCE() in softnet_seq_show() */
+	WRITE_ONCE(sd->received_rps, sd->received_rps + 1);
 }
 
 #endif /* CONFIG_RPS */
@@ -7523,7 +7524,8 @@ static __latent_entropy void net_rx_action(void)
 		 */
 		if (unlikely(budget <= 0 ||
 			     time_after_eq(jiffies, time_limit))) {
-			sd->time_squeeze++;
+			/* Pairs with READ_ONCE() in softnet_seq_show() */
+			WRITE_ONCE(sd->time_squeeze, sd->time_squeeze + 1);
 			break;
 		}
 	}

net/core/net-procfs.c

@@ -145,11 +145,11 @@ static int softnet_seq_show(struct seq_file *seq, void *v)
 	seq_printf(seq,
 		   "%08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x "
 		   "%08x %08x\n",
-		   sd->processed, atomic_read(&sd->dropped),
-		   sd->time_squeeze, 0,
+		   READ_ONCE(sd->processed), atomic_read(&sd->dropped),
+		   READ_ONCE(sd->time_squeeze), 0,
 		   0, 0, 0, 0, /* was fastroute */
 		   0,	/* was cpu_collision */
-		   sd->received_rps, flow_limit_count,
+		   READ_ONCE(sd->received_rps), flow_limit_count,
 		   input_qlen + process_qlen, (int)seq->index,
 		   input_qlen, process_qlen);
 	return 0;