Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Yanfei Xu <yanfei.xu@windriver.com>
To:     peterz@infradead.org, mingo@redhat.com, will@kernel.org,
        longman@redhat.com, boqun.feng@gmail.com
Cc:     linux-kernel@vger.kernel.org
Subject: [PATCH] locking/rwsem: Introduce __rwsem_spin_on_owner()
Date:   Sat, 16 Oct 2021 02:32:55 +0800
Message-Id: <20211015183255.3788750-1-yanfei.xu@windriver.com>
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?e/K5RPZdktkFkDbFVgTP3tiTQPYo0cbepVPHDETUrTrFbn1waCwOiCGQLBdy?=
 =?us-ascii?Q?x6x6wu3pHTQAWVM0IhddmFCoSsf/IfoUGDlJzpLuU6kjrZFemyK5T50629LY?=
 =?us-ascii?Q?kfGxAJ/+lRZ3XrUfLzsezkKvX+JDCHuEI37TY+gqcrojpVCyUHEsWbwyy8u7?=
 =?us-ascii?Q?2CnPEE2QP+SA9SwDEihrgUM6PzX22jIO/paAUZPlBUolLXE2OMPGwEHnd800?=
 =?us-ascii?Q?sCSejwjSOItbtSIBOXU0ZkxNH3/ptw6iCDN/NjaaFhjszVVrF6GsDEimrBzd?=
 =?us-ascii?Q?WhiAxQn0GHofz3ozpk00xuujxrID4qan9HXj6jZW6eUfwoLK21N4mZEsYg27?=
 =?us-ascii?Q?XontMa9iUh7eRkRaL04jFR4vb3G6zP41gqmZwrpqeXHScuoLbNIYzmD8iYWm?=
 =?us-ascii?Q?XGf7s4ZvfWa5jVhPj/+tbUKjXvOJzaLr6Z3NSmcu+TDyaqvgm/znKGE3+qnf?=
 =?us-ascii?Q?/FCRYE6lAkCAq64tnxS0Dp7n9Dl8Yduk/wMuA+BuEV23IXBKqioiD57bSOa5?=
 =?us-ascii?Q?yZFbu0Cwm/a+5d+FozmRZ+VTeOhMSLxjh4ANGOnMoYn5tpEN4K3GQDYkMH2D?=
 =?us-ascii?Q?k2FTFfTP5WptF7mA6IjMH9CuUplp9Rjbeq1NrPE52COppkGHwcAFT20+3qq4?=
 =?us-ascii?Q?5+B/QLTdLfvtnl6D53q+jDj9wKCx8B0e+3dSeY2fs4KkDJGagSWdQKaLZGs9?=
 =?us-ascii?Q?BmCj9xVGqaDQJ9h27gJrJiS9mU4EXUzlcBSzAJEw1sSpmhy78sYDWyyypizU?=
 =?us-ascii?Q?FK8XBSBahgKjBLTSPOsVQFCbot83iwTh8qcivP3rs5H77gJM377Zw5PluFRP?=
 =?us-ascii?Q?iRWRPyGEfWt2f/2Obc7ic/mtnpsrQn0deb08Cec6SQ2TTnfNcn9J0oGdqHbM?=
 =?us-ascii?Q?b0DvGw+SZjCLdQCD+SyB2zN7JXLmNSYVDAXXbC1/5XsjTj4/avck38ULStav?=
 =?us-ascii?Q?f2g+qYTt/qem05YwiCsb+ir+VlP4p9sKIl8LA8PXQqPFqP0+hM9aBTGB/cok?=
 =?us-ascii?Q?NLA8QYDV696o+4odCKMd6O/kso8/ztWjEjPNRgxk3jZn4C6HwqIzsvBll6Lb?=
 =?us-ascii?Q?aFpPy05vJevCQ7b7VEfFPQBQkYTCdeIlg0X3pCqdMSPzlUqUAUm/JmtAFd83?=
 =?us-ascii?Q?5aYvXuXqPOdpGdAt/DJVlDm3TJXnvC8pD6QECAEUOS/8Rdg3mr80huvlxZPO?=
 =?us-ascii?Q?O6r+rf8Q/Z2dWUyrYHw1iyZ1Z1dmCAXrw7XenrRGCPwiwAyvZ0rhx9FhjWtr?=
 =?us-ascii?Q?q26xa0S8PZ/Loo+laQcLiiDSvdZIPT9qBlZVLHt8UnCGyEmqvF4TagVJjJY1?=
 =?us-ascii?Q?6nGZjiCwMVFndLI8QFfFFNTq?=
X-OriginatorOrg: windriver.com
X-MS-Exchange-CrossTenant-Network-Message-Id: d85c5484-5eda-485f-41bc-08d9900a3c47
X-MS-Exchange-CrossTenant-AuthSource: DM8PR11MB5734.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Oct 2021 18:33:08.7380
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 8ddb2873-a1ad-4a18-ae4e-4644631433be
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: CppVSlnm5jCavUM3jCm56+GZXxQuWNpu2wjUkf6t57tdI3l/bMwSbxrthPw4HiW0qYdTi7FeLUrLB6q6/idtQw==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR11MB4201
X-Proofpoint-GUID: dqn9W2JMGaytInGweXHL_Rj4RabQfqE6
X-Proofpoint-ORIG-GUID: dqn9W2JMGaytInGweXHL_Rj4RabQfqE6
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.182.1,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.0.607.475
 definitions=2021-10-15_06,2021-10-14_02,2020-04-07_01
X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=535
 lowpriorityscore=0 adultscore=0 spamscore=0 priorityscore=1501
 malwarescore=0 mlxscore=0 suspectscore=0 clxscore=1015 bulkscore=0
 phishscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx
 scancount=1 engine=8.12.0-2109230001 definitions=main-2110150112
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

'enum owner_state' is only declared when CONFIG_RWSEM_SPIN_ON_OWNER
is selected. To avoid the build failure, we introduce
__rwsem_spin_on_owner function.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
---
 kernel/locking/rwsem.c | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 2bd914187399..7d85c85ad8a5 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -634,7 +634,7 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
 }
 
 /*
- * The rwsem_spin_on_owner() function returns the following 4 values
+ * The __rwsem_spin_on_owner() function returns the following 4 values
  * depending on the lock owner state.
  *   OWNER_NULL  : owner is currently NULL
  *   OWNER_WRITER: when owner changes and is a writer
@@ -665,7 +665,7 @@ rwsem_owner_state(struct task_struct *owner, unsigned long flags)
 }
 
 static noinline enum owner_state
-rwsem_spin_on_owner(struct rw_semaphore *sem)
+__rwsem_spin_on_owner(struct rw_semaphore *sem)
 {
 	struct task_struct *new, *owner;
 	unsigned long flags, new_flags;
@@ -712,6 +712,17 @@ rwsem_spin_on_owner(struct rw_semaphore *sem)
 	return state;
 }
 
+static inline enum owner_state
+rwsem_spin_on_owner(struct rw_semaphore *sem)
+{
+	enum owner_state state;
+
+	preempt_disable();
+	state = __rwsem_spin_on_owner(sem);
+	preempt_enable();
+	return state;
+}
+
 /*
  * Calculate reader-owned rwsem spinning threshold for writer
  *
@@ -759,7 +770,7 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem)
 	for (;;) {
 		enum owner_state owner_state;
 
-		owner_state = rwsem_spin_on_owner(sem);
+		owner_state = __rwsem_spin_on_owner(sem);
 		if (!(owner_state & OWNER_SPINNABLE))
 			break;
 
@@ -831,7 +842,7 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem)
 		 * quit spinning.
 		 *
 		 * If the owner is a writer, the need_resched() check is
-		 * done inside rwsem_spin_on_owner(). If the owner is not
+		 * done inside __rwsem_spin_on_owner(). If the owner is not
 		 * a writer, need_resched() check needs to be done here.
 		 */
 		if (owner_state != OWNER_WRITER) {
@@ -1023,7 +1034,6 @@ rwsem_down_write_slowpath(struct rw_semaphore *sem, int state)
 	enum writer_wait_state wstate;
 	struct rwsem_waiter waiter;
 	struct rw_semaphore *ret = sem;
-	enum owner_state owner_state;
 	DEFINE_WAKE_Q(wake_q);
 
 	/* do optimistic spinning and steal lock if possible */
@@ -1099,12 +1109,9 @@ rwsem_down_write_slowpath(struct rw_semaphore *sem, int state)
 		 * In this case, we attempt to acquire the lock again
 		 * without sleeping.
 		 */
-		if (wstate == WRITER_HANDOFF) {
-			preempt_disable();
-			owner_state = rwsem_spin_on_owner(sem);
-			preempt_enable();
-			if (owner_state == OWNER_NULL)
-				goto trylock_again;
+		if (wstate == WRITER_HANDOFF &&
+		    rwsem_spin_on_owner(sem) == OWNER_NULL) {
+			goto trylock_again;
 		}
 
 		/* Block until there are no active lockers. */
-- 
2.27.0