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rds: Fix incorrect statistics counting 

In rds_send_xmit() there is logic to batch the sends. However, if
another thread has acquired the lock and has incremented the send_gen,
it is considered a race and we yield. The code incrementing the
s_send_lock_queue_raced statistics counter did not count this event
correctly.

This commit counts the race condition correctly.

Changes from v1:
- Removed check for *someone_on_xmit()*
- Fixed incorrect indentation

Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Reviewed-by: Knut Omang <knut.omang@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Håkon Bugge 2017-09-06 18:35:51 +02:00 committed by David S. Miller
parent eef5a7cc2a
commit 126f760ca9
1 changed files with 7 additions and 3 deletions
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10
net/rds/send.c
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@ -428,14 +428,18 @@ over_batch:
* some work and we will skip our goto
*/
if (ret == 0) {
bool raced;
smp_mb();
raced = send_gen != READ_ONCE(cp->cp_send_gen);
if ((test_bit(0, &conn->c_map_queued) ||
!list_empty(&cp->cp_send_queue)) &&
send_gen == READ_ONCE(cp->cp_send_gen)) {
rds_stats_inc(s_send_lock_queue_raced);
!list_empty(&cp->cp_send_queue)) && !raced) {
if (batch_count < send_batch_count)
goto restart;
queue_delayed_work(rds_wq, &cp->cp_send_w, 1);
} else if (raced) {
rds_stats_inc(s_send_lock_queue_raced);
}
}
out: