[tip:locking/core] x86, locking/rwlocks: Enable qrwlocks on x86

[tip-bot for Waiman Long]

Commit-ID:  bd01ec1a13f9a327950c8e3080096446c7804753
Gitweb:     http://git.kernel.org/tip/bd01ec1a13f9a327950c8e3080096446c7804753
Author:     Waiman Long <Waiman.Long@xxxxxx>
AuthorDate: Mon, 3 Feb 2014 13:18:57 +0100
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 6 Jun 2014 07:58:29 +0200

x86, locking/rwlocks: Enable qrwlocks on x86

Make x86 use the fair rwlock_t.

Implement the custom queue_write_unlock() for best performance.

Signed-off-by: Waiman Long <Waiman.Long@xxxxxx>
[peterz: near complete rewrite]
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Dave Jones <davej@xxxxxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
Cc: "Paul E.McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: x86@xxxxxxxxxx
Link: http://lkml.kernel.org/n/tip-r1xuzmdysvuhl3h86n5fbxi7@xxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/Kconfig                      |  1 +
 arch/x86/include/asm/qrwlock.h        | 17 +++++++++++++++++
 arch/x86/include/asm/spinlock.h       |  4 ++++
 arch/x86/include/asm/spinlock_types.h |  4 ++++
 4 files changed, 26 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 25d2c6f..bf7626f 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -121,6 +121,7 @@ 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
diff --git a/arch/x86/include/asm/qrwlock.h b/arch/x86/include/asm/qrwlock.h
new file mode 100644
index 0000000..70f46f0
--- /dev/null
+++ b/arch/x86/include/asm/qrwlock.h
@@ -0,0 +1,17 @@
+#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 */
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index 0f62f54..54f1c80 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -187,6 +187,7 @@ static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
 		cpu_relax();
 }
 
+#ifndef CONFIG_QUEUE_RWLOCK
 /*
  * Read-write spinlocks, allowing multiple readers
  * but only one writer.
@@ -269,6 +270,9 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
 	asm volatile(LOCK_PREFIX WRITE_LOCK_ADD(%1) "%0"
 		     : "+m" (rw->write) : "i" (RW_LOCK_BIAS) : "memory");
 }
+#else
+#include <asm/qrwlock.h>
+#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)
diff --git a/arch/x86/include/asm/spinlock_types.h b/arch/x86/include/asm/spinlock_types.h
index 4f1bea1..73c4c00 100644
--- 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-generic/qrwlock_types.h>
+#else
 #include <asm/rwlock.h>
+#endif
 
 #endif /* _ASM_X86_SPINLOCK_TYPES_H */
--
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