From e04ec0de61c1eb9693179093e83ab8ca68a30d08 Mon Sep 17 00:00:00 2001

From: Daniel Jordan <daniel.m.jordan@oracle.com>

Date: Mon, 8 Jun 2020 17:26:52 -0400

Subject: [PATCH] padata: upgrade smp_mb__after_atomic to smp_mb in

 padata_do_serial

Git-commit: e04ec0de61c1eb9693179093e83ab8ca68a30d08

Patch-mainline: v5.8-rc4

References: bsc#1178648

A 5.7 kernel hangs during a tcrypt test of padata that waits for an AEAD

request to finish.  This is only seen on large machines running many

concurrent requests.

The issue is that padata never serializes the request.  The removal of

the reorder_objects atomic missed that the memory barrier in

padata_do_serial() depends on it.

Upgrade the barrier from smp_mb__after_atomic to smp_mb to get correct

ordering again.

Fixes: 3facced7aeed1 ("padata: remove reorder_objects")

Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>

Cc: Steffen Klassert <steffen.klassert@secunet.com>

Cc: linux-kernel@vger.kernel.org

Cc: <stable@vger.kernel.org>

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Signed-off-by: Oliver Neukum <oneukum@suse.com>

---

 kernel/padata.c | 4 ++--

 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/padata.c b/kernel/padata.c

index 29fc5d87a4cd..4373f7adaa40 100644

--- a/kernel/padata.c

+++ b/kernel/padata.c

@@ -335,7 +335,7 @@ static void padata_reorder(struct parallel_data *pd)

 	 *

 	 * Ensure reorder queue is read after pd->lock is dropped so we see

 	 * new objects from another task in padata_do_serial.  Pairs with

-	 * smp_mb__after_atomic in padata_do_serial.

+	 * smp_mb in padata_do_serial.

 	 */

 	smp_mb();

@@ -418,7 +418,7 @@ void padata_do_serial(struct padata_priv *padata)

 	 * with the trylock of pd->lock in padata_reorder.  Pairs with smp_mb

 	 * in padata_reorder.

 	 */

-	smp_mb__after_atomic();

+	smp_mb();

 	padata_reorder(pd);

 }

-- 

2.26.2