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locking/percpu-rwsem: Remove preempt_disable variants

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Effective revert commit:

  87709e28dc ("fs/locks: Use percpu_down_read_preempt_disable()")

This is causing major pain for PREEMPT_RT.

Sebastian did a lot of lockperf runs on 2 and 4 node machines with all
preemption modes (PREEMPT=n should be an obvious NOP for this patch
and thus serves as a good control) and no results showed significance
over 2-sigma (the PREEMPT=n results were almost empty at 1-sigma).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra
2019-02-21 15:38:40 +01:00
committed by Ingo Molnar
parent 0614621d89
commit 02e525b2af
2 changed files with 20 additions and 36 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
include/linux/percpu-rwsem.h
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@@ -29,7 +29,7 @@ static struct percpu_rw_semaphore name = { \
extern int __percpu_down_read(struct percpu_rw_semaphore *, int);
extern void __percpu_up_read(struct percpu_rw_semaphore *);
static inline void percpu_down_read_preempt_disable(struct percpu_rw_semaphore *sem)
static inline void percpu_down_read(struct percpu_rw_semaphore *sem)
{
might_sleep();
@@ -47,16 +47,10 @@ static inline void percpu_down_read_preempt_disable(struct percpu_rw_semaphore *
__this_cpu_inc(*sem->read_count);
if (unlikely(!rcu_sync_is_idle(&sem->rss)))
__percpu_down_read(sem, false); /* Unconditional memory barrier */
barrier();
/*
* The barrier() prevents the compiler from
* The preempt_enable() prevents the compiler from
* bleeding the critical section out.
*/
}
static inline void percpu_down_read(struct percpu_rw_semaphore *sem)
{
percpu_down_read_preempt_disable(sem);
preempt_enable();
}
@@ -83,13 +77,9 @@ static inline int percpu_down_read_trylock(struct percpu_rw_semaphore *sem)
return ret;
}
static inline void percpu_up_read_preempt_enable(struct percpu_rw_semaphore *sem)
static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
{
/*
* The barrier() prevents the compiler from
* bleeding the critical section out.
*/
barrier();
preempt_disable();
/*
* Same as in percpu_down_read().
*/
@@ -102,12 +92,6 @@ static inline void percpu_up_read_preempt_enable(struct percpu_rw_semaphore *sem
rwsem_release(&sem->rw_sem.dep_map, 1, _RET_IP_);
}
static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
{
preempt_disable();
percpu_up_read_preempt_enable(sem);
}
extern void percpu_down_write(struct percpu_rw_semaphore *);
extern void percpu_up_write(struct percpu_rw_semaphore *);