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authorBen Gardon <bgardon@google.com>2021-02-02 21:57:12 +0300
committerPaolo Bonzini <pbonzini@redhat.com>2021-02-04 13:27:42 +0300
commit26128cb6c7e6731fe644c687af97733adfdb5ee9 (patch)
tree2f6ab60c7c1c4c020980b8fe98937915320c74a6
parent7cca2d0b7e7d9f3cd740d41afdc00051c9b508a0 (diff)
downloadlinux-26128cb6c7e6731fe644c687af97733adfdb5ee9.tar.xz
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>
-rw-r--r--include/asm-generic/qrwlock.h24
-rw-r--r--include/linux/rwlock.h7
2 files changed, 25 insertions, 6 deletions
diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h
index 84ce841ce735..0020d3b820a7 100644
--- a/include/asm-generic/qrwlock.h
+++ b/include/asm-generic/qrwlock.h
@@ -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 */
diff --git a/include/linux/rwlock.h b/include/linux/rwlock.h
index 3dcd617e65ae..7ce9a51ae5c0 100644
--- a/include/linux/rwlock.h
+++ b/include/linux/rwlock.h
@@ -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 */