* [memnic PATCH v2] pmd: fix race condition @ 2014-04-03 6:35 Hiroshi Shimamoto [not found] ` <7F861DC0615E0C47A872E6F3C5FCDDBD0109D398-ZmjkEB1lVlLt6d3pZDjeaEtBU8KWyXPq@public.gmane.org> 0 siblings, 1 reply; 3+ messages in thread From: Hiroshi Shimamoto @ 2014-04-03 6:35 UTC (permalink / raw) To: Thomas Monjalon; +Cc: dev-VfR2kkLFssw, Hayato Momma From: Hiroshi Shimamoto <h-shimamoto-ehU+Cx/zZe18UrSeD/g0lQ@public.gmane.org> There is a race condition, on transmit to host. 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-ehU+Cx/zZe18UrSeD/g0lQ@public.gmane.org> Reviewed-by: Hayato Momma <h-momma-JhyGz2TFV9J8UrSeD/g0lQ@public.gmane.org> --- pmd/pmd_memnic.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/pmd/pmd_memnic.c b/pmd/pmd_memnic.c index d833130..4a1c1e4 100644 --- a/pmd/pmd_memnic.c +++ b/pmd/pmd_memnic.c @@ -345,6 +345,15 @@ retry: goto retry; } + if (idx != ACCESS_ONCE(adapter->down_idx)) { + /* + * 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; adapter->down_idx = idx; -- 1.8.4 ^ permalink raw reply related [flat|nested] 3+ messages in thread
[parent not found: <7F861DC0615E0C47A872E6F3C5FCDDBD0109D398-ZmjkEB1lVlLt6d3pZDjeaEtBU8KWyXPq@public.gmane.org>]
* Re: [memnic PATCH v2] pmd: fix race condition [not found] ` <7F861DC0615E0C47A872E6F3C5FCDDBD0109D398-ZmjkEB1lVlLt6d3pZDjeaEtBU8KWyXPq@public.gmane.org> @ 2014-04-11 14:41 ` Olivier MATZ 2014-04-11 15:46 ` Thomas Monjalon 0 siblings, 1 reply; 3+ messages in thread From: Olivier MATZ @ 2014-04-11 14:41 UTC (permalink / raw) To: Hiroshi Shimamoto; +Cc: dev-VfR2kkLFssw, Hayato Momma On Thursday, April 03, 2014 06:35:06 AM Hiroshi Shimamoto wrote: > From: Hiroshi Shimamoto <h-shimamoto-ehU+Cx/zZe18UrSeD/g0lQ@public.gmane.org> > > There is a race condition, on transmit to host. > > 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-ehU+Cx/zZe18UrSeD/g0lQ@public.gmane.org> > Reviewed-by: Hayato Momma <h-momma-JhyGz2TFV9J8UrSeD/g0lQ@public.gmane.org> > --- > pmd/pmd_memnic.c | 9 +++++++++ > 1 file changed, 9 insertions(+) Reviewed-by: Olivier Matz <olivier.matz-pdR9zngts4EAvxtiuMwx3w@public.gmane.org> ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [memnic PATCH v2] pmd: fix race condition 2014-04-11 14:41 ` Olivier MATZ @ 2014-04-11 15:46 ` Thomas Monjalon 0 siblings, 0 replies; 3+ messages in thread From: Thomas Monjalon @ 2014-04-11 15:46 UTC (permalink / raw) To: Hiroshi Shimamoto; +Cc: dev-VfR2kkLFssw, Hayato Momma 2014-04-11 16:41, Olivier MATZ: > On Thursday, April 03, 2014 06:35:06 AM Hiroshi Shimamoto wrote: > > From: Hiroshi Shimamoto <h-shimamoto-ehU+Cx/zZe18UrSeD/g0lQ@public.gmane.org> > > > > There is a race condition, on transmit to host. > > > > 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-ehU+Cx/zZe18UrSeD/g0lQ@public.gmane.org> > > Reviewed-by: Hayato Momma <h-momma-JhyGz2TFV9J8UrSeD/g0lQ@public.gmane.org> > > Reviewed-by: Olivier Matz <olivier.matz-pdR9zngts4EAvxtiuMwx3w@public.gmane.org> Applied Thanks -- Thomas ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2014-04-11 15:46 UTC | newest] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2014-04-03 6:35 [memnic PATCH v2] pmd: fix race condition Hiroshi Shimamoto [not found] ` <7F861DC0615E0C47A872E6F3C5FCDDBD0109D398-ZmjkEB1lVlLt6d3pZDjeaEtBU8KWyXPq@public.gmane.org> 2014-04-11 14:41 ` Olivier MATZ 2014-04-11 15:46 ` Thomas Monjalon
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