dql: annotate data-races around dql->last_obj_cnt

dql->last_obj_cnt is read/written from different contexts, without any lock synchronization. Use READ_ONCE()/WRITE_ONCE() to avoid load/store tearing. Signed-off-by: Eric Dumazet <[email protected]> Reviewed-by: Joe Damato <[email protected]> Link: https://patch.msgid.link/[email protected] Signed-off-by: Jakub Kicinski <[email protected]>
kdave · Nov 1, 2024 · a911bad · a911bad
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diff --git a/include/linux/dynamic_queue_limits.h b/include/linux/dynamic_queue_limits.h
@@ -127,7 +127,7 @@ static inline void dql_queued(struct dql *dql, unsigned int count)
 	if (WARN_ON_ONCE(count > DQL_MAX_OBJECT))
 		return;
 
-	dql->last_obj_cnt = count;
+	WRITE_ONCE(dql->last_obj_cnt, count);
 
 	/* We want to force a write first, so that cpu do not attempt
 	 * to get cache line containing last_obj_cnt, num_queued, adj_limit

diff --git a/lib/dynamic_queue_limits.c b/lib/dynamic_queue_limits.c
@@ -179,7 +179,7 @@ void dql_completed(struct dql *dql, unsigned int count)
 
 	dql->adj_limit = limit + completed;
 	dql->prev_ovlimit = ovlimit;
-	dql->prev_last_obj_cnt = dql->last_obj_cnt;
+	dql->prev_last_obj_cnt = READ_ONCE(dql->last_obj_cnt);
 	dql->num_completed = completed;
 	dql->prev_num_queued = num_queued;