From: Takeshi Yoshimura <t.yoshimura8869@gmail.com>
To: dev@dpdk.org
Cc: Takeshi Yoshimura <t.yoshimura8869@gmail.com>,
stable@dpdk.org, Takeshi Yoshimura <tyos@jp.ibm.com>
Subject: [dpdk-dev] [PATCH] rte_ring: fix racy dequeue/enqueue in ppc64
Date: Thu, 12 Jul 2018 11:44:14 +0900 [thread overview]
Message-ID: <20180712024414.4756-1-t.yoshimura8869@gmail.com> (raw)
SPDK blobfs encountered a crash around rte_ring dequeues in ppc64.
It uses a single consumer and multiple producers for a rte_ring.
The problem was a load-load reorder in rte_ring_sc_dequeue_bulk().
The reordered loads happened on r->prod.tail in
__rte_ring_move_cons_head() (rte_ring_generic.h) and ring[idx] in
DEQUEUE_PTRS() (rte_ring.h). They have a load-load control
dependency, but the code does not satisfy it. Note that they are
not reordered if __rte_ring_move_cons_head() with is_sc != 1 because
cmpset invokes a read barrier.
The paired stores on these loads are in ENQUEUE_PTRS() and
update_tail(). Simplified code around the reorder is the following.
Consumer Producer
load idx[ring]
store idx[ring]
store r->prod.tail
load r->prod.tail
In this case, the consumer loads old idx[ring] and confirms the load
is valid with the new r->prod.tail.
I added a read barrier in the case where __IS_SC is passed to
__rte_ring_move_cons_head(). I also fixed __rte_ring_move_prod_head()
to avoid similar problems with a single producer.
Cc: stable@dpdk.org
Signed-off-by: Takeshi Yoshimura <tyos@jp.ibm.com>
---
lib/librte_ring/rte_ring_generic.h | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/lib/librte_ring/rte_ring_generic.h b/lib/librte_ring/rte_ring_generic.h
index ea7dbe5b9..477326180 100644
--- a/lib/librte_ring/rte_ring_generic.h
+++ b/lib/librte_ring/rte_ring_generic.h
@@ -90,9 +90,10 @@ __rte_ring_move_prod_head(struct rte_ring *r, unsigned int is_sp,
return 0;
*new_head = *old_head + n;
- if (is_sp)
+ if (is_sp) {
+ rte_smp_rmb();
r->prod.head = *new_head, success = 1;
- else
+ } else
success = rte_atomic32_cmpset(&r->prod.head,
*old_head, *new_head);
} while (unlikely(success == 0));
@@ -158,9 +159,10 @@ __rte_ring_move_cons_head(struct rte_ring *r, unsigned int is_sc,
return 0;
*new_head = *old_head + n;
- if (is_sc)
+ if (is_sc) {
+ rte_smp_rmb();
r->cons.head = *new_head, success = 1;
- else
+ } else
success = rte_atomic32_cmpset(&r->cons.head, *old_head,
*new_head);
} while (unlikely(success == 0));
--
2.17.1
next reply other threads:[~2018-07-12 2:44 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-12 2:44 Takeshi Yoshimura [this message]
2018-07-12 17:08 ` Jerin Jacob
2018-07-17 2:54 ` Takeshi Yoshimura
2018-07-17 3:34 ` Jerin Jacob
2021-03-24 21:45 ` [dpdk-dev] [dpdk-stable] " Thomas Monjalon
2021-03-28 1:00 ` Honnappa Nagarahalli
2021-06-16 7:14 ` [dpdk-dev] 回复: " Feifei Wang
2021-06-16 16:37 ` [dpdk-dev] " Honnappa Nagarahalli
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