[dpdk-stable] patch 'rwlock: reimplement with atomic builtins' has been queued to LTS release 18.11.2

[Kevin Traynor]

Hi,

FYI, your patch has been queued to LTS release 18.11.2

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 04/24/19. 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.

Kevin Traynor

---
>From 55c7ea8fcc0b3eb07f4c7bbbf9cf60da44661861 Mon Sep 17 00:00:00 2001
From: Joyce Kong <joyce.kong at arm.com>
Date: Mon, 25 Mar 2019 17:14:57 +0800
Subject: [PATCH] rwlock: reimplement with atomic builtins

[ upstream commit e8af2f1f11c8f35430086806988d43ff78414ba5 ]

The __sync builtin based implementation generates full memory
barriers ('dmb ish') on Arm platforms. Using C11 atomic builtins
to generate one way barriers.

Here is the assembly code of __sync_compare_and_swap builtin.
__sync_bool_compare_and_swap(dst, exp, src);
   0x000000000090f1b0 <+16>:    e0 07 40 f9 ldr x0, [sp, #8]
   0x000000000090f1b4 <+20>:    e1 0f 40 79 ldrh    w1, [sp, #6]
   0x000000000090f1b8 <+24>:    e2 0b 40 79 ldrh    w2, [sp, #4]
   0x000000000090f1bc <+28>:    21 3c 00 12 and w1, w1, #0xffff
   0x000000000090f1c0 <+32>:    03 7c 5f 48 ldxrh   w3, [x0]
   0x000000000090f1c4 <+36>:    7f 00 01 6b cmp w3, w1
   0x000000000090f1c8 <+40>:    61 00 00 54 b.ne    0x90f1d4
<rte_atomic16_cmpset+52>  // b.any
   0x000000000090f1cc <+44>:    02 fc 04 48 stlxrh  w4, w2, [x0]
   0x000000000090f1d0 <+48>:    84 ff ff 35 cbnz    w4, 0x90f1c0
<rte_atomic16_cmpset+32>
   0x000000000090f1d4 <+52>:    bf 3b 03 d5 dmb ish
   0x000000000090f1d8 <+56>:    e0 17 9f 1a cset    w0, eq  // eq = none

Fixes: af75078fece3 ("first public release")

Signed-off-by: Gavin Hu <gavin.hu at arm.com>
Signed-off-by: Joyce Kong <joyce.kong at arm.com>
Tested-by: Joyce Kong <joyce.kong at arm.com>
Acked-by: Jerin Jacob <jerinj at marvell.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
---
 .../common/include/generic/rte_rwlock.h          | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/lib/librte_eal/common/include/generic/rte_rwlock.h b/lib/librte_eal/common/include/generic/rte_rwlock.h
index 5751a0e6d..2c284f0b5 100644
--- a/lib/librte_eal/common/include/generic/rte_rwlock.h
+++ b/lib/librte_eal/common/include/generic/rte_rwlock.h
@@ -65,5 +65,5 @@ rte_rwlock_read_lock(rte_rwlock_t *rwl)
 
 	while (success == 0) {
-		x = rwl->cnt;
+		x = __atomic_load_n(&rwl->cnt, __ATOMIC_RELAXED);
 		/* write lock is held */
 		if (x < 0) {
@@ -71,6 +71,6 @@ rte_rwlock_read_lock(rte_rwlock_t *rwl)
 			continue;
 		}
-		success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
-					      (uint32_t)x, (uint32_t)(x + 1));
+		success = __atomic_compare_exchange_n(&rwl->cnt, &x, x + 1, 1,
+					__ATOMIC_ACQUIRE, __ATOMIC_RELAXED);
 	}
 }
@@ -85,5 +85,5 @@ static inline void
 rte_rwlock_read_unlock(rte_rwlock_t *rwl)
 {
-	rte_atomic32_dec((rte_atomic32_t *)(intptr_t)&rwl->cnt);
+	__atomic_fetch_sub(&rwl->cnt, 1, __ATOMIC_RELEASE);
 }
 
@@ -101,5 +101,5 @@ rte_rwlock_write_lock(rte_rwlock_t *rwl)
 
 	while (success == 0) {
-		x = rwl->cnt;
+		x = __atomic_load_n(&rwl->cnt, __ATOMIC_RELAXED);
 		/* a lock is held */
 		if (x != 0) {
@@ -107,6 +107,6 @@ rte_rwlock_write_lock(rte_rwlock_t *rwl)
 			continue;
 		}
-		success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
-					      0, (uint32_t)-1);
+		success = __atomic_compare_exchange_n(&rwl->cnt, &x, -1, 1,
+					__ATOMIC_ACQUIRE, __ATOMIC_RELAXED);
 	}
 }
@@ -121,5 +121,5 @@ static inline void
 rte_rwlock_write_unlock(rte_rwlock_t *rwl)
 {
-	rte_atomic32_inc((rte_atomic32_t *)(intptr_t)&rwl->cnt);
+	__atomic_store_n(&rwl->cnt, 0, __ATOMIC_RELEASE);
 }
 
-- 
2.20.1

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2019-04-16 15:34:27.821461788 +0100
+++ 0059-rwlock-reimplement-with-atomic-builtins.patch	2019-04-16 15:34:25.236178707 +0100
@@ -1,8 +1,10 @@
-From e8af2f1f11c8f35430086806988d43ff78414ba5 Mon Sep 17 00:00:00 2001
+From 55c7ea8fcc0b3eb07f4c7bbbf9cf60da44661861 Mon Sep 17 00:00:00 2001
 From: Joyce Kong <joyce.kong at arm.com>
 Date: Mon, 25 Mar 2019 17:14:57 +0800
 Subject: [PATCH] rwlock: reimplement with atomic builtins
 
+[ upstream commit e8af2f1f11c8f35430086806988d43ff78414ba5 ]
+
 The __sync builtin based implementation generates full memory
 barriers ('dmb ish') on Arm platforms. Using C11 atomic builtins
 to generate one way barriers.
@@ -24,7 +26,6 @@
    0x000000000090f1d8 <+56>:    e0 17 9f 1a cset    w0, eq  // eq = none
 
 Fixes: af75078fece3 ("first public release")
-Cc: stable at dpdk.org
 
 Signed-off-by: Gavin Hu <gavin.hu at arm.com>
 Signed-off-by: Joyce Kong <joyce.kong at arm.com>
@@ -32,11 +33,11 @@
 Acked-by: Jerin Jacob <jerinj at marvell.com>
 Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
 ---
- .../common/include/generic/rte_rwlock.h       | 29 ++++++++++---------
- 1 file changed, 15 insertions(+), 14 deletions(-)
+ .../common/include/generic/rte_rwlock.h          | 16 ++++++++--------
+ 1 file changed, 8 insertions(+), 8 deletions(-)
 
 diff --git a/lib/librte_eal/common/include/generic/rte_rwlock.h b/lib/librte_eal/common/include/generic/rte_rwlock.h
-index b05d85aee..31608fa2e 100644
+index 5751a0e6d..2c284f0b5 100644
 --- a/lib/librte_eal/common/include/generic/rte_rwlock.h
 +++ b/lib/librte_eal/common/include/generic/rte_rwlock.h
 @@ -65,5 +65,5 @@ rte_rwlock_read_lock(rte_rwlock_t *rwl)
@@ -55,48 +56,21 @@
 +					__ATOMIC_ACQUIRE, __ATOMIC_RELAXED);
  	}
  }
-@@ -96,11 +96,12 @@ rte_rwlock_read_trylock(rte_rwlock_t *rwl)
- 
- 	while (success == 0) {
--		x = rwl->cnt;
-+		x = __atomic_load_n(&rwl->cnt, __ATOMIC_RELAXED);
- 		/* write lock is held */
- 		if (x < 0)
- 			return -EBUSY;
--		success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
--					      (uint32_t)x, (uint32_t)(x + 1));
-+		success = __atomic_compare_exchange_n(&rwl->cnt, &x, x + 1, 1,
-+					__ATOMIC_ACQUIRE, __ATOMIC_RELAXED);
- 	}
-+
- 	return 0;
- }
-@@ -115,5 +116,5 @@ static inline void
+@@ -85,5 +85,5 @@ static inline void
  rte_rwlock_read_unlock(rte_rwlock_t *rwl)
  {
 -	rte_atomic32_dec((rte_atomic32_t *)(intptr_t)&rwl->cnt);
 +	__atomic_fetch_sub(&rwl->cnt, 1, __ATOMIC_RELEASE);
  }
  
-@@ -136,7 +137,7 @@ rte_rwlock_write_trylock(rte_rwlock_t *rwl)
- 	int32_t x;
- 
--	x = rwl->cnt;
--	if (x != 0 || rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
--				0, (uint32_t)-1) == 0)
-+	x = __atomic_load_n(&rwl->cnt, __ATOMIC_RELAXED);
-+	if (x != 0 || __atomic_compare_exchange_n(&rwl->cnt, &x, -1, 1,
-+			      __ATOMIC_ACQUIRE, __ATOMIC_RELAXED) == 0)
- 		return -EBUSY;
- 
-@@ -157,5 +158,5 @@ rte_rwlock_write_lock(rte_rwlock_t *rwl)
+@@ -101,5 +101,5 @@ rte_rwlock_write_lock(rte_rwlock_t *rwl)
  
  	while (success == 0) {
 -		x = rwl->cnt;
 +		x = __atomic_load_n(&rwl->cnt, __ATOMIC_RELAXED);
  		/* a lock is held */
  		if (x != 0) {
-@@ -163,6 +164,6 @@ rte_rwlock_write_lock(rte_rwlock_t *rwl)
+@@ -107,6 +107,6 @@ rte_rwlock_write_lock(rte_rwlock_t *rwl)
  			continue;
  		}
 -		success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
@@ -105,7 +79,7 @@
 +					__ATOMIC_ACQUIRE, __ATOMIC_RELAXED);
  	}
  }
-@@ -177,5 +178,5 @@ static inline void
+@@ -121,5 +121,5 @@ static inline void
  rte_rwlock_write_unlock(rte_rwlock_t *rwl)
  {
 -	rte_atomic32_inc((rte_atomic32_t *)(intptr_t)&rwl->cnt);