[PATCH v3 2/2] qspinlock, x86: Enable x86-64 to use queue spinlock

From: Waiman Long <Waiman.Long@hp.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Arnd Bergmann <arnd@arndb.de>
Cc: linux-arch@vger.kernel.org, x86@kernel.org,
	linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Michel Lespinasse <walken@google.com>,
	Andi Kleen <andi@firstfloor.org>, Rik van Riel <riel@redhat.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
	George Spelvin <linux@horizon.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Daniel J Blueman <daniel@numascale.com>,
	Alexander Fyodorov <halcy@yandex.ru>,
	Aswin Chandramouleeswaran <aswin@hp.com>,
	Scott J Norton <scott.norton@hp.com>,
	Thavatchai Makphaibulchoke <thavatchai.makpahibulchoke@hp.com>,
	Waiman Long <Waiman.Long@hp.com>
Subject: [PATCH v3 2/2] qspinlock, x86: Enable x86-64 to use queue spinlock
Date: Tue, 28 Jan 2014 13:19:11 -0500	[thread overview]
Message-ID: <1390933151-1797-3-git-send-email-Waiman.Long@hp.com> (raw)
In-Reply-To: <1390933151-1797-1-git-send-email-Waiman.Long@hp.com>

This patch makes the necessary changes at the x86 architecture
specific layer to enable the use of queue spinlock for x86-64. As
x86-32 machines are typically not multi-socket. The benefit of queue
spinlock may not be apparent. So queue spinlock is not enabled.

Currently, there is some incompatibilities between the para-virtualized
spinlock code (which hard-codes the use of ticket spinlock) and the
queue spinlock. Therefore, the use of queue spinlock is disabled when
the para-virtualized spinlock is enabled.

Signed-off-by: Waiman Long <Waiman.Long@hp.com>
---
 arch/x86/Kconfig                      |    1 +
 arch/x86/include/asm/spinlock.h       |    2 ++
 arch/x86/include/asm/spinlock_types.h |    4 ++++
 3 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 03db714..50692b4 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -17,6 +17,7 @@ config X86_64
 	depends on 64BIT
 	select X86_DEV_DMA_OPS
 	select ARCH_USE_CMPXCHG_LOCKREF
+	select ARCH_USE_QUEUE_SPINLOCK
 
 ### Arch settings
 config X86
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index bf156de..cfe51a6 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -43,6 +43,7 @@
 extern struct static_key paravirt_ticketlocks_enabled;
 static __always_inline bool static_key_false(struct static_key *key);
 
+#ifndef CONFIG_QUEUE_SPINLOCK
 #ifdef CONFIG_PARAVIRT_SPINLOCKS
 
 static inline void __ticket_enter_slowpath(arch_spinlock_t *lock)
@@ -181,6 +182,7 @@ static __always_inline void arch_spin_lock_flags(arch_spinlock_t *lock,
 {
 	arch_spin_lock(lock);
 }
+#endif /* !CONFIG_QUEUE_SPINLOCK */
 
 static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
 {
diff --git a/arch/x86/include/asm/spinlock_types.h b/arch/x86/include/asm/spinlock_types.h
index 4f1bea1..f501a2a 100644
--- a/arch/x86/include/asm/spinlock_types.h
+++ b/arch/x86/include/asm/spinlock_types.h
@@ -11,6 +11,9 @@
 #define TICKET_SLOWPATH_FLAG	((__ticket_t)0)
 #endif
 
+#ifdef CONFIG_QUEUE_SPINLOCK
+#include <asm-generic/qspinlock.h>
+#else
 #if (CONFIG_NR_CPUS < (256 / __TICKET_LOCK_INC))
 typedef u8  __ticket_t;
 typedef u16 __ticketpair_t;
@@ -33,6 +36,7 @@ typedef struct arch_spinlock {
 } arch_spinlock_t;
 
 #define __ARCH_SPIN_LOCK_UNLOCKED	{ { 0 } }
+#endif /* CONFIG_QUEUE_SPINLOCK */
 
 #include <asm/rwlock.h>
 
-- 
1.7.1

