[dpdk-stable] patch 'distributor: fix handshake synchronization' has been queued to stable release 19.11.6

[luca.boccassi at gmail.com]

Hi,

FYI, your patch has been queued to stable release 19.11.6

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 10/30/20. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Thanks.

Luca Boccassi

---
>From c4f615c8172d4fa24d2e8486bfe0b0386b13838e Mon Sep 17 00:00:00 2001
From: Lukasz Wojciechowski <l.wojciechow at partner.samsung.com>
Date: Sat, 17 Oct 2020 05:06:45 +0200
Subject: [PATCH] distributor: fix handshake synchronization

[ upstream commit bea84d5592eb2658cf8c36214a9db75d398efa1c ]

rte_distributor_return_pkt function which is run on worker cores
must wait for distributor core to clear handshake on retptr64
before using those buffers. While the handshake is set distributor
core controls buffers and any operations on worker side might overwrite
buffers which are unread yet.
Same situation appears in the legacy single distributor. Function
rte_distributor_return_pkt_single shouldn't modify the bufptr64 until
handshake on it is cleared by distributor lcore.

Fixes: 775003ad2f96 ("distributor: add new burst-capable library")

Signed-off-by: Lukasz Wojciechowski <l.wojciechow at partner.samsung.com>
Acked-by: David Hunt <david.hunt at intel.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>
---
 lib/librte_distributor/rte_distributor.c        | 12 ++++++++++++
 lib/librte_distributor/rte_distributor_single.c |  4 ++++
 2 files changed, 16 insertions(+)

diff --git a/lib/librte_distributor/rte_distributor.c b/lib/librte_distributor/rte_distributor.c
index 1c047f065a..c6b19a3886 100644
--- a/lib/librte_distributor/rte_distributor.c
+++ b/lib/librte_distributor/rte_distributor.c
@@ -169,6 +169,18 @@ rte_distributor_return_pkt(struct rte_distributor *d,
 			return -EINVAL;
 	}
 
+	/* Spin while handshake bits are set (scheduler clears it).
+	 * Sync with worker on GET_BUF flag.
+	 */
+	while (unlikely(__atomic_load_n(&(buf->retptr64[0]), __ATOMIC_RELAXED)
+			& RTE_DISTRIB_GET_BUF)) {
+		rte_pause();
+		uint64_t t = rte_rdtsc()+100;
+
+		while (rte_rdtsc() < t)
+			rte_pause();
+	}
+
 	/* Sync with distributor to acquire retptrs */
 	__atomic_thread_fence(__ATOMIC_ACQUIRE);
 	for (i = 0; i < RTE_DIST_BURST_SIZE; i++)
diff --git a/lib/librte_distributor/rte_distributor_single.c b/lib/librte_distributor/rte_distributor_single.c
index abaf7730c3..f4725b1d0b 100644
--- a/lib/librte_distributor/rte_distributor_single.c
+++ b/lib/librte_distributor/rte_distributor_single.c
@@ -74,6 +74,10 @@ rte_distributor_return_pkt_single(struct rte_distributor_single *d,
 	union rte_distributor_buffer_single *buf = &d->bufs[worker_id];
 	uint64_t req = (((int64_t)(uintptr_t)oldpkt) << RTE_DISTRIB_FLAG_BITS)
 			| RTE_DISTRIB_RETURN_BUF;
+	while (unlikely(__atomic_load_n(&buf->bufptr64, __ATOMIC_RELAXED)
+			& RTE_DISTRIB_FLAGS_MASK))
+		rte_pause();
+
 	/* Sync with distributor on RETURN_BUF flag. */
 	__atomic_store_n(&(buf->bufptr64), req, __ATOMIC_RELEASE);
 	return 0;
-- 
2.20.1

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2020-10-28 10:35:17.363747343 +0000
+++ 0182-distributor-fix-handshake-synchronization.patch	2020-10-28 10:35:11.796834322 +0000
@@ -1,8 +1,10 @@
-From bea84d5592eb2658cf8c36214a9db75d398efa1c Mon Sep 17 00:00:00 2001
+From c4f615c8172d4fa24d2e8486bfe0b0386b13838e Mon Sep 17 00:00:00 2001
 From: Lukasz Wojciechowski <l.wojciechow at partner.samsung.com>
 Date: Sat, 17 Oct 2020 05:06:45 +0200
 Subject: [PATCH] distributor: fix handshake synchronization
 
+[ upstream commit bea84d5592eb2658cf8c36214a9db75d398efa1c ]
+
 rte_distributor_return_pkt function which is run on worker cores
 must wait for distributor core to clear handshake on retptr64
 before using those buffers. While the handshake is set distributor
@@ -13,7 +15,6 @@
 handshake on it is cleared by distributor lcore.
 
 Fixes: 775003ad2f96 ("distributor: add new burst-capable library")
-Cc: stable at dpdk.org
 
 Signed-off-by: Lukasz Wojciechowski <l.wojciechow at partner.samsung.com>
 Acked-by: David Hunt <david.hunt at intel.com>