Commit 6b79349a authored Aug 14, 2023 by Ben Gardon Committed by Yu Zhang Nov 21, 2023

sched: Add needbreak for rwlocks

mainline inclusion
from mainline-v5.12-rc1
commit a09a689a
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I7S3VQ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a09a689a534183c48f200bc2de1ae61ae9c462ad



----------------------------------------------------------------------

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>
Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>

parent 2bb655c5

include/linux/sched.h

+17 −0

Original line number	Diff line number	Diff line
		@@ -2024,6 +2024,23 @@ 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());