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101 lines
2.6 KiB
Diff
101 lines
2.6 KiB
Diff
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Wed, 4 Sep 2019 17:59:36 +0200
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Subject: [PATCH] percpu-refcount: use normal instead of RCU-sched"
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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This is a revert of commit
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a4244454df129 ("percpu-refcount: use RCU-sched insted of normal RCU")
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which claims the only reason for using RCU-sched is
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"rcu_read_[un]lock() … are slightly more expensive than preempt_disable/enable()"
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and
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"As the RCU critical sections are extremely short, using sched-RCU
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shouldn't have any latency implications."
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The problem with RCU-sched is that it disables preemption and the
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callback must not acquire any sleeping locks like spinlock_t on
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PREEMPT_RT which is the case.
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Convert back to normal RCU.
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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include/linux/percpu-refcount.h | 16 ++++++++--------
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1 file changed, 8 insertions(+), 8 deletions(-)
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--- a/include/linux/percpu-refcount.h
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+++ b/include/linux/percpu-refcount.h
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@@ -186,14 +186,14 @@ static inline void percpu_ref_get_many(s
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{
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unsigned long __percpu *percpu_count;
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- rcu_read_lock_sched();
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+ rcu_read_lock();
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if (__ref_is_percpu(ref, &percpu_count))
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this_cpu_add(*percpu_count, nr);
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else
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atomic_long_add(nr, &ref->count);
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- rcu_read_unlock_sched();
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+ rcu_read_unlock();
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}
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/**
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@@ -223,7 +223,7 @@ static inline bool percpu_ref_tryget(str
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unsigned long __percpu *percpu_count;
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bool ret;
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- rcu_read_lock_sched();
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+ rcu_read_lock();
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if (__ref_is_percpu(ref, &percpu_count)) {
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this_cpu_inc(*percpu_count);
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@@ -232,7 +232,7 @@ static inline bool percpu_ref_tryget(str
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ret = atomic_long_inc_not_zero(&ref->count);
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}
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- rcu_read_unlock_sched();
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+ rcu_read_unlock();
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return ret;
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}
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@@ -257,7 +257,7 @@ static inline bool percpu_ref_tryget_liv
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unsigned long __percpu *percpu_count;
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bool ret = false;
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- rcu_read_lock_sched();
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+ rcu_read_lock();
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if (__ref_is_percpu(ref, &percpu_count)) {
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this_cpu_inc(*percpu_count);
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@@ -266,7 +266,7 @@ static inline bool percpu_ref_tryget_liv
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ret = atomic_long_inc_not_zero(&ref->count);
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}
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- rcu_read_unlock_sched();
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+ rcu_read_unlock();
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return ret;
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}
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@@ -285,14 +285,14 @@ static inline void percpu_ref_put_many(s
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{
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unsigned long __percpu *percpu_count;
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- rcu_read_lock_sched();
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+ rcu_read_lock();
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if (__ref_is_percpu(ref, &percpu_count))
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this_cpu_sub(*percpu_count, nr);
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else if (unlikely(atomic_long_sub_and_test(nr, &ref->count)))
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ref->release(ref);
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- rcu_read_unlock_sched();
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+ rcu_read_unlock();
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}
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/**
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