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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>
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1 parent 25426b7 commit 914bec1011a25f65cdc94988a6f974bfb9a3c10d @hiroa-ki hiroa-ki committed with davem330 May 30, 2012
Showing with 7 additions and 5 deletions.
  1. +7 −5 lib/dynamic_queue_limits.c
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@@ -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);

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