From: Oleg Nesterov <oleg@redhat.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>,
Waiman Long <longman@redhat.com>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Davidlohr Bueso <dave@stgolabs.net>,
"Theodore Y. Ts'o" <tytso@mit.edu>,
Amir Goldstein <amir73il@gmail.com>, Jan Kara <jack@suse.cz>
Subject: [PATCH] locking/rwsem: simplify the is-owner-spinnable checks
Date: Fri, 18 May 2018 18:55:35 +0200 [thread overview]
Message-ID: <20180518165534.GA22348@redhat.com> (raw)
In-Reply-To: <20180518094052.GA26150@gmail.com>
Add the trivial owner_on_cpu() helper for rwsem_can_spin_on_owner() and
rwsem_spin_on_owner(), it also allows to make rwsem_can_spin_on_owner()
a bit more clear.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/locking/rwsem-xadd.c | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)
diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index a903367..3064c50 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -347,6 +347,15 @@ static inline bool rwsem_try_write_lock_unqueued(struct rw_semaphore *sem)
}
}
+static inline bool owner_on_cpu(struct task_struct *owner)
+{
+ /*
+ * As lock holder preemption issue, we both skip spinning if
+ * task is not on cpu or its cpu is preempted
+ */
+ return owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));
+}
+
static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
{
struct task_struct *owner;
@@ -359,17 +368,10 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
rcu_read_lock();
owner = READ_ONCE(sem->owner);
- if (!owner || !is_rwsem_owner_spinnable(owner)) {
- ret = !owner; /* !owner is spinnable */
- goto done;
+ if (owner) {
+ ret = is_rwsem_owner_spinnable(owner) &&
+ owner_on_cpu(owner);
}
-
- /*
- * As lock holder preemption issue, we both skip spinning if task is not
- * on cpu or its cpu is preempted
- */
- ret = owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));
-done:
rcu_read_unlock();
return ret;
}
@@ -398,8 +400,7 @@ static noinline bool rwsem_spin_on_owner(struct rw_semaphore *sem)
* abort spinning when need_resched or owner is not running or
* owner's cpu is preempted.
*/
- if (!owner->on_cpu || need_resched() ||
- vcpu_is_preempted(task_cpu(owner))) {
+ if (need_resched() || !owner_on_cpu(owner)) {
rcu_read_unlock();
return false;
}
--
2.5.0
next prev parent reply other threads:[~2018-05-18 16:55 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-15 21:49 [PATCH v4 0/2] locking/rwsem: Fix DEBUG_RWSEM warning from thaw_super() Waiman Long
2018-05-15 21:49 ` [PATCH v4 1/2] locking/rwsem: Add a new RWSEM_ANONYMOUSLY_OWNED flag Waiman Long
2018-05-16 10:48 ` Oleg Nesterov
2018-05-16 11:59 ` Peter Zijlstra
2018-05-16 13:11 ` Waiman Long
2018-05-16 15:27 ` Oleg Nesterov
2018-05-16 12:19 ` Matthew Wilcox
2018-05-18 7:02 ` Ingo Molnar
2018-05-18 8:41 ` Oleg Nesterov
2018-05-18 9:40 ` Ingo Molnar
2018-05-18 16:55 ` Oleg Nesterov [this message]
2018-05-18 17:00 ` [PATCH] locking/rwsem: simplify the is-owner-spinnable checks Waiman Long
2018-05-15 21:49 ` [PATCH v4 2/2] locking/percpu-rwsem: Annotate rwsem ownership transfer by setting RWSEM_OWNER_UNKNOWN Waiman Long
2018-05-16 5:37 ` Amir Goldstein
2018-05-16 13:17 ` Waiman Long
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