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Date: Tue, 05 Nov 2013 09:42:39 -0800
From: Tim Chen <tim.c.chen@...ux.intel.com>
To: Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org, linux-mm <linux-mm@...ck.org>,
linux-arch@...r.kernel.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
Waiman Long <waiman.long@...com>,
Andrea Arcangeli <aarcange@...hat.com>,
Alex Shi <alex.shi@...aro.org>,
Andi Kleen <andi@...stfloor.org>,
Michel Lespinasse <walken@...gle.com>,
Davidlohr Bueso <davidlohr.bueso@...com>,
Matthew R Wilcox <matthew.r.wilcox@...el.com>,
Dave Hansen <dave.hansen@...el.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Rik van Riel <riel@...hat.com>,
Peter Hurley <peter@...leysoftware.com>,
"Paul E.McKenney" <paulmck@...ux.vnet.ibm.com>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
George Spelvin <linux@...izon.com>,
"H. Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
Aswin Chandramouleeswaran <aswin@...com>,
Scott J Norton <scott.norton@...com>,
Will Deacon <will.deacon@....com>
Subject: [PATCH v2 4/4] MCS Lock: Make mcs_spinlock.h includable in other
files
The following changes are made to enable mcs_spinlock.h file to be
widely included in other files without causing problem:
1) Include a number of prerequisite header files and define
arch_mutex_cpu_relax(), if not previously defined.
2) Make mcs_spin_unlock() an inlined function and
rename mcs_spin_lock() to _raw_mcs_spin_lock() which is also an
inlined function.
3) Create a new mcs_spinlock.c file to contain the non-inlined
mcs_spin_lock() function.
Signed-off-by: Waiman Long <Waiman.Long@...com>
---
include/linux/mcs_spinlock.h | 27 ++++++++++++++++++++++-----
kernel/Makefile | 6 +++---
kernel/mcs_spinlock.c | 21 +++++++++++++++++++++
3 files changed, 46 insertions(+), 8 deletions(-)
create mode 100644 kernel/mcs_spinlock.c
diff --git a/include/linux/mcs_spinlock.h b/include/linux/mcs_spinlock.h
index 93d445d..f2c71e8 100644
--- a/include/linux/mcs_spinlock.h
+++ b/include/linux/mcs_spinlock.h
@@ -12,11 +12,27 @@
#ifndef __LINUX_MCS_SPINLOCK_H
#define __LINUX_MCS_SPINLOCK_H
+/*
+ * asm/processor.h may define arch_mutex_cpu_relax().
+ * If it is not defined, cpu_relax() will be used.
+ */
+#include <asm/barrier.h>
+#include <asm/cmpxchg.h>
+#include <asm/processor.h>
+#include <linux/compiler.h>
+
+#ifndef arch_mutex_cpu_relax
+# define arch_mutex_cpu_relax() cpu_relax()
+#endif
+
struct mcs_spinlock {
struct mcs_spinlock *next;
int locked; /* 1 if lock acquired */
};
+extern
+void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node);
+
/*
* In order to acquire the lock, the caller should declare a local node and
* pass a reference of the node to this function in addition to the lock.
@@ -24,11 +40,11 @@ struct mcs_spinlock {
* on this node->locked until the previous lock holder sets the node->locked
* in mcs_spin_unlock().
*
- * We don't inline mcs_spin_lock() so that perf can correctly account for the
- * time spent in this lock function.
+ * The _raw_mcs_spin_lock() function should not be called directly. Instead,
+ * users should call mcs_spin_lock().
*/
-static noinline
-void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
+static inline
+void _raw_mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
{
struct mcs_spinlock *prev;
@@ -55,7 +71,8 @@ void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
* Releases the lock. The caller should pass in the corresponding node that
* was used to acquire the lock.
*/
-static void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
+static inline
+void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
{
struct mcs_spinlock *next = ACCESS_ONCE(node->next);
diff --git a/kernel/Makefile b/kernel/Makefile
index 1ce4755..2ad8454 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -50,9 +50,9 @@ obj-$(CONFIG_SMP) += smp.o
ifneq ($(CONFIG_SMP),y)
obj-y += up.o
endif
-obj-$(CONFIG_SMP) += spinlock.o
-obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
-obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
+obj-$(CONFIG_SMP) += spinlock.o mcs_spinlock.o
+obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o mcs_spinlock.o
+obj-$(CONFIG_PROVE_LOCKING) += spinlock.o mcs_spinlock.o
obj-$(CONFIG_UID16) += uid16.o
obj-$(CONFIG_MODULES) += module.o
obj-$(CONFIG_MODULE_SIG) += module_signing.o modsign_pubkey.o modsign_certificate.o
diff --git a/kernel/mcs_spinlock.c b/kernel/mcs_spinlock.c
new file mode 100644
index 0000000..3c55626
--- /dev/null
+++ b/kernel/mcs_spinlock.c
@@ -0,0 +1,21 @@
+/*
+ * MCS lock
+ *
+ * The MCS lock (proposed by Mellor-Crummey and Scott) is a simple spin-lock
+ * with the desirable properties of being fair, and with each cpu trying
+ * to acquire the lock spinning on a local variable.
+ * It avoids expensive cache bouncings that common test-and-set spin-lock
+ * implementations incur.
+ */
+#include <linux/mcs_spinlock.h>
+#include <linux/export.h>
+
+/*
+ * We don't inline mcs_spin_lock() so that perf can correctly account for the
+ * time spent in this lock function.
+ */
+void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
+{
+ _raw_mcs_spin_lock(lock, node);
+}
+EXPORT_SYMBOL_GPL(mcs_spin_lock);
--
1.7.4.4
--
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