From: Peter Zijlstra <peterz@infradead.org>
To: peterz@infradead.org, mingo@kernel.org, will@kernel.org
Cc: oleg@redhat.com, tglx@linutronix.de,
linux-kernel@vger.kernel.org, bigeasy@linutronix.de,
juri.lelli@redhat.com, williams@redhat.com, bristot@redhat.com,
longman@redhat.com, dave@stgolabs.net, jack@suse.com
Subject: [PATCH 3/5] locking/percpu-rwsem: Move __this_cpu_inc() into the slowpath
Date: Wed, 13 Nov 2019 11:21:18 +0100 [thread overview]
Message-ID: <20191113102855.811146018@infradead.org> (raw)
In-Reply-To: 20191113102115.116470462@infradead.org
As preparation to rework __percpu_down_read() move the
__this_cpu_inc() into it.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
include/linux/percpu-rwsem.h | 10 ++++++----
kernel/locking/percpu-rwsem.c | 2 ++
2 files changed, 8 insertions(+), 4 deletions(-)
--- a/include/linux/percpu-rwsem.h
+++ b/include/linux/percpu-rwsem.h
@@ -59,8 +59,9 @@ static inline void percpu_down_read(stru
* and that once the synchronize_rcu() is done, the writer will see
* anything we did within this RCU-sched read-size critical section.
*/
- __this_cpu_inc(*sem->read_count);
- if (unlikely(!rcu_sync_is_idle(&sem->rss)))
+ if (likely(rcu_sync_is_idle(&sem->rss)))
+ __this_cpu_inc(*sem->read_count);
+ else
__percpu_down_read(sem, false); /* Unconditional memory barrier */
/*
* The preempt_enable() prevents the compiler from
@@ -77,8 +78,9 @@ static inline bool percpu_down_read_tryl
/*
* Same as in percpu_down_read().
*/
- __this_cpu_inc(*sem->read_count);
- if (unlikely(!rcu_sync_is_idle(&sem->rss)))
+ if (likely(rcu_sync_is_idle(&sem->rss)))
+ __this_cpu_inc(*sem->read_count);
+ else
ret = __percpu_down_read(sem, true); /* Unconditional memory barrier */
preempt_enable();
/*
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -47,6 +47,8 @@ EXPORT_SYMBOL_GPL(percpu_free_rwsem);
bool __percpu_down_read(struct percpu_rw_semaphore *sem, bool try)
{
+ __this_cpu_inc(*sem->read_count);
+
/*
* Due to having preemption disabled the decrement happens on
* the same CPU as the increment, avoiding the
next prev parent reply other threads:[~2019-11-13 10:29 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-13 10:21 [PATCH 0/5] locking: Percpu-rwsem rewrite Peter Zijlstra
2019-11-13 10:21 ` [PATCH 1/5] locking/percpu-rwsem, lockdep: Make percpu-rwsem use its own lockdep_map Peter Zijlstra
2019-11-15 20:39 ` Davidlohr Bueso
2020-01-08 1:33 ` [PATCH] locking/percpu-rwsem: Add might_sleep() for writer locking Davidlohr Bueso
2020-01-08 1:33 ` Davidlohr Bueso
2020-02-11 12:48 ` [tip: locking/core] " tip-bot2 for Davidlohr Bueso
2019-11-13 10:21 ` [PATCH 2/5] locking/percpu-rwsem: Convert to bool Peter Zijlstra
2019-11-13 10:21 ` Peter Zijlstra [this message]
2019-11-13 10:21 ` [PATCH 4/5] locking/percpu-rwsem: Extract __percpu_down_read_trylock() Peter Zijlstra
2019-11-18 16:28 ` Oleg Nesterov
2019-11-13 10:21 ` [PATCH 5/5] locking/percpu-rwsem: Remove the embedded rwsem Peter Zijlstra
2019-11-18 19:53 ` Davidlohr Bueso
2019-11-18 23:19 ` Davidlohr Bueso
2019-12-17 10:45 ` Peter Zijlstra
2019-12-17 10:35 ` Peter Zijlstra
2019-11-18 21:52 ` Waiman Long
2019-12-17 10:28 ` Peter Zijlstra
2019-11-19 13:50 ` Waiman Long
2019-11-19 15:58 ` Oleg Nesterov
2019-11-19 16:28 ` Waiman Long
2019-12-17 10:26 ` Peter Zijlstra
2019-12-17 10:28 ` Peter Zijlstra
2019-11-15 17:14 ` [PATCH 0/5] locking: Percpu-rwsem rewrite Juri Lelli
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