From: Hiroshi Shimamoto <h-shimam...@ct.jp.nec.com>
There is a race condition, on transmit to vSwitch.
Guest PMD Host
Thread-A Thread-B vSwitch
|idx=0 |idx=0 |p[0] st!=2
|cmpxchg | |
|p[0] st->1 | |
|idx=1 | |
|fill data | |
|p[0] st->2 | |p[0] st==2
| | |receive data
| | |p[0] st->0
| |cmpxchg |
| |success |p[1] st!=2
| |p[0] st->1 |
This is BAD
That causes traffic stop.
We have to take care about that race condition with checking
whether current index is correct.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto at ct.jp.nec.com>
Reviewed-by: Hayato Momma <h-momma at ce.jp.nec.com>
---
pmd/pmd_memnic.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/pmd/pmd_memnic.c b/pmd/pmd_memnic.c
index 30d5a1b..805f0b2 100644
--- a/pmd/pmd_memnic.c
+++ b/pmd/pmd_memnic.c
@@ -278,6 +278,15 @@ retry:
goto retry;
}
+ if (idx != ACCESS_ONCE(adapter->down_idx)) {
+ /*
+ * vSwitch freed this and got false positive,
+ * need to recover the status and retry.
+ */
+ p->status = MEMNIC_PKT_ST_FREE;
+ goto retry;
+ }
+
if (++idx >= MEMNIC_NR_PACKET)
idx = 0;
adapter->down_idx = idx;
--
1.8.4
