Make x86 use the fair rwlock_t.
Implement the custom queue_write_unlock() for best performance.
Signed-off-by: Waiman Long <waiman.l...@hp.com>
[peterz: near complete rewrite]
Signed-off-by: Peter Zijlstra <pet...@infradead.org>
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/qrwlock.h | 18 ++++++++++++++++++
arch/x86/include/asm/spinlock.h | 2 ++
arch/x86/include/asm/spinlock_types.h | 4 ++++
4 files changed, 25 insertions(+)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -119,6 +119,7 @@ config X86
select MODULES_USE_ELF_RELA if X86_64
select CLONE_BACKWARDS if X86_32
select ARCH_USE_BUILTIN_BSWAP
+ select ARCH_USE_QUEUE_RWLOCK
select OLD_SIGSUSPEND3 if X86_32 || IA32_EMULATION
select OLD_SIGACTION if X86_32
select COMPAT_OLD_SIGACTION if IA32_EMULATION
--- /dev/null
+++ b/arch/x86/include/asm/qrwlock.h
@@ -0,0 +1,18 @@
+#ifndef _ASM_X86_QRWLOCK_H
+#define _ASM_X86_QRWLOCK_H
+
+#include <asm-generic/qrwlock_types.h>
+
+#if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE)
+#define queue_write_unlock queue_write_unlock
+static inline void queue_write_unlock(struct qrwlock *lock)
+{
+ barrier();
+ ACCESS_ONCE(*(u8 *)&lock->cnts) = 0;
+}
+#endif
+
+#include <asm-generic/qrwlock.h>
+
+#endif /* _ASM_X86_QRWLOCK_H */
+
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -188,6 +188,7 @@ static inline void arch_spin_unlock_wait
cpu_relax();
}
+#ifndef CONFIG_QUEUE_RWLOCK
/*
* Read-write spinlocks, allowing multiple readers
* but only one writer.
@@ -270,6 +271,7 @@ static inline void arch_write_unlock(arc
asm volatile(LOCK_PREFIX WRITE_LOCK_ADD(%1) "%0"
: "+m" (rw->write) : "i" (RW_LOCK_BIAS) : "memory");
}
+#endif /* CONFIG_QUEUE_RWLOCK */
#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
--- a/arch/x86/include/asm/spinlock_types.h
+++ b/arch/x86/include/asm/spinlock_types.h
@@ -34,6 +34,10 @@ typedef struct arch_spinlock {
#define __ARCH_SPIN_LOCK_UNLOCKED { { 0 } }
+#ifdef CONFIG_QUEUE_RWLOCK
+#include <asm/qrwlock.h>
+#else
#include <asm/rwlock.h>
+#endif
#endif /* _ASM_X86_SPINLOCK_TYPES_H */
--
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