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sched: Add needbreak for rwlocks 

Contention awareness while holding a spin lock is essential for reducing
latency when long running kernel operations can hold that lock. Add the
same contention detection interface for read/write spin locks.

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: <20210202185734.1680553-8-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Ben Gardon 2021-02-02 10:57:13 -08:00 committed by Paolo Bonzini
parent 26128cb6c7
commit a09a689a53
1 changed files with 17 additions and 0 deletions
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17
include/linux/sched.h
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@ -1912,6 +1912,23 @@ static inline int spin_needbreak(spinlock_t *lock)
#endif
}
/*
* Check if a rwlock is contended.
* Returns non-zero if there is another task waiting on the rwlock.
* Returns zero if the lock is not contended or the system / underlying
* rwlock implementation does not support contention detection.
* Technically does not depend on CONFIG_PREEMPTION, but a general need
* for low latency.
*/
static inline int rwlock_needbreak(rwlock_t *lock)
{
#ifdef CONFIG_PREEMPTION
return rwlock_is_contended(lock);
#else
return 0;
#endif
}
static __always_inline bool need_resched(void)
{
return unlikely(tif_need_resched());