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locking/rwlocks: Add contention detection for rwlocks 

rwlocks do not currently have any facility to detect contention
like spinlocks do. In order to allow users of rwlocks to better manage
latency, add contention detection for queued rwlocks.

CC: Ingo Molnar <mingo@redhat.com>
CC: Will Deacon <will@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-7-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
master
Ben Gardon 2021-02-02 10:57:12 -08:00 committed by Paolo Bonzini
parent 7cca2d0b7e
commit 26128cb6c7
2 changed files with 25 additions and 6 deletions
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24
include/asm-generic/qrwlock.h
View File

@ -14,6 +14,7 @@
#include <asm/processor.h>
#include <asm-generic/qrwlock_types.h>
#include <asm-generic/qspinlock.h>
/*
* Writer states & reader shift and bias.
@ -116,15 +117,26 @@ static inline void queued_write_unlock(struct qrwlock *lock)
smp_store_release(&lock->wlocked, 0);
}
/**
* queued_rwlock_is_contended - check if the lock is contended
* @lock : Pointer to queue rwlock structure
* Return: 1 if lock contended, 0 otherwise
*/
static inline int queued_rwlock_is_contended(struct qrwlock *lock)
{
return arch_spin_is_locked(&lock->wait_lock);
}
/*
* Remapping rwlock architecture specific functions to the corresponding
* queue rwlock functions.
*/
#define arch_read_lock(l) queued_read_lock(l)
#define arch_write_lock(l) queued_write_lock(l)
#define arch_read_trylock(l) queued_read_trylock(l)
#define arch_write_trylock(l) queued_write_trylock(l)
#define arch_read_unlock(l) queued_read_unlock(l)
#define arch_write_unlock(l) queued_write_unlock(l)
#define arch_read_lock(l) queued_read_lock(l)
#define arch_write_lock(l) queued_write_lock(l)
#define arch_read_trylock(l) queued_read_trylock(l)
#define arch_write_trylock(l) queued_write_trylock(l)
#define arch_read_unlock(l) queued_read_unlock(l)
#define arch_write_unlock(l) queued_write_unlock(l)
#define arch_rwlock_is_contended(l) queued_rwlock_is_contended(l)
#endif /* __ASM_GENERIC_QRWLOCK_H */

7
include/linux/rwlock.h
View File

@ -128,4 +128,11 @@ do { \
1 : ({ local_irq_restore(flags); 0; }); \
})
#ifdef arch_rwlock_is_contended
#define rwlock_is_contended(lock) \
arch_rwlock_is_contended(&(lock)->raw_lock)
#else
#define rwlock_is_contended(lock) ((void)(lock), 0)
#endif /* arch_rwlock_is_contended */
#endif /* __LINUX_RWLOCK_H */