bql: Avoid possible inconsistent calculation.

dql->num_queued could change while processing dql_completed(). To provide consistent calculation, added an on stack variable. Signed-off-by: Hiroaki SHIMODA <[email protected]> Cc: Tom Herbert <[email protected]> Cc: Eric Dumazet <[email protected]> Cc: Denys Fedoryshchenko <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> Signed-off-by: David S. Miller <[email protected]>
Axel1400 · May 31, 2012 · 914bec1 · 914bec1
1 parent 25426b7
commit 914bec1
Showing 1 changed file with 7 additions and 5 deletions.
diff --git a/lib/dynamic_queue_limits.c b/lib/dynamic_queue_limits.c
@@ -17,16 +17,18 @@
 void dql_completed(struct dql *dql, unsigned int count)
 {
 	unsigned int inprogress, prev_inprogress, limit;
-	unsigned int ovlimit, completed;
+	unsigned int ovlimit, completed, num_queued;
 	bool all_prev_completed;
 
+	num_queued = ACCESS_ONCE(dql->num_queued);
+
 	/* Can't complete more than what's in queue */
-	BUG_ON(count > dql->num_queued - dql->num_completed);
+	BUG_ON(count > num_queued - dql->num_completed);
 
 	completed = dql->num_completed + count;
 	limit = dql->limit;
-	ovlimit = POSDIFF(dql->num_queued - dql->num_completed, limit);
-	inprogress = dql->num_queued - completed;
+	ovlimit = POSDIFF(num_queued - dql->num_completed, limit);
+	inprogress = num_queued - completed;
 	prev_inprogress = dql->prev_num_queued - dql->num_completed;
 	all_prev_completed = AFTER_EQ(completed, dql->prev_num_queued);
 
@@ -106,7 +108,7 @@ void dql_completed(struct dql *dql, unsigned int count)
 	dql->prev_ovlimit = ovlimit;
 	dql->prev_last_obj_cnt = dql->last_obj_cnt;
 	dql->num_completed = completed;
-	dql->prev_num_queued = dql->num_queued;
+	dql->prev_num_queued = num_queued;
 }
 EXPORT_SYMBOL(dql_completed);