* [dpdk-dev] [memnic PATCH] linux: fix race condition
@ 2014-04-03 7:35 Hiroshi Shimamoto
2014-04-11 9:41 ` Olivier MATZ
0 siblings, 1 reply; 3+ messages in thread
From: Hiroshi Shimamoto @ 2014-04-03 7:35 UTC (permalink / raw)
To: dev; +Cc: Hayato Momma
From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Same as PMD, there is a race condition between host and guest
in the guest MEMNIC kernel driver.
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
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
---
linux/memnic_net.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/linux/memnic_net.c b/linux/memnic_net.c
index 9019258..fadece6 100644
--- a/linux/memnic_net.c
+++ b/linux/memnic_net.c
@@ -209,6 +209,15 @@ retry:
goto retry;
}
+ if (idx != ACCESS_ONCE(memnic->down)) {
+ /*
+ * host 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;
memnic->down = idx;
--
1.8.4
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [dpdk-dev] [memnic PATCH] linux: fix race condition
2014-04-03 7:35 [dpdk-dev] [memnic PATCH] linux: fix race condition Hiroshi Shimamoto
@ 2014-04-11 9:41 ` Olivier MATZ
2014-04-11 15:47 ` Thomas Monjalon
0 siblings, 1 reply; 3+ messages in thread
From: Olivier MATZ @ 2014-04-11 9:41 UTC (permalink / raw)
To: dev
On Thursday, April 03, 2014 07:35:50 AM Hiroshi Shimamoto wrote:
> From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
>
> Same as PMD, there is a race condition between host and guest
> in the guest MEMNIC kernel driver.
>
> 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
>
> Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
> ---
> linux/memnic_net.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
Reviewed-by: Olivier Matz <olivier.matz@6wind.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [dpdk-dev] [memnic PATCH] linux: fix race condition
2014-04-11 9:41 ` Olivier MATZ
@ 2014-04-11 15:47 ` Thomas Monjalon
0 siblings, 0 replies; 3+ messages in thread
From: Thomas Monjalon @ 2014-04-11 15:47 UTC (permalink / raw)
To: Olivier MATZ; +Cc: dev
2014-04-11 11:41, Olivier MATZ:
> On Thursday, April 03, 2014 07:35:50 AM Hiroshi Shimamoto wrote:
> > From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
> >
> > Same as PMD, there is a race condition between host and guest
> > in the guest MEMNIC kernel driver.
> >
> > 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
> >
> > Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
> > ---
> >
> > linux/memnic_net.c | 9 +++++++++
> > 1 file changed, 9 insertions(+)
>
> Reviewed-by: Olivier Matz <olivier.matz@6wind.com>
Applied
Thanks
--
Thomas
^ permalink raw reply [flat|nested] 3+ messages in thread
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2014-04-03 7:35 [dpdk-dev] [memnic PATCH] linux: fix race condition Hiroshi Shimamoto
2014-04-11 9:41 ` Olivier MATZ
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