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 <shimoda.hiroaki@gmail.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Denys Fedoryshchenko <denys@visp.net.lb>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 5 deletions

diff --git a/lib/dynamic_queue_limits.c b/lib/dynamic_queue_limits.c
index 0fafa77f4036..0777c5a45fa0 100644
--- 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);