[PATCH 24/29] x86, tsx: Use adaptive elision for mutexes

Andi Kleen
2013-03-23T01:31:17Z

Add the elision adaption state to struct mutex and use elide_adapt()
This allows mutexes that do not elide to automatically disable
elision on themselves for some time. This means we have a fail-safe
for mutexes that do not elide well and do not need to annotate
very mutex.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
arch/x86/include/asm/mutex.h | 20 +++++++++++++++-----
arch/x86/kernel/rtm-locks.c | 10 ++++++++--
include/linux/mutex.h | 3 +++
3 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/mutex.h b/arch/x86/include/asm/mutex.h
index 7f585e3..bb9cf9d 100644
--- a/arch/x86/include/asm/mutex.h
+++ b/arch/x86/include/asm/mutex.h
@@ -10,8 +10,10 @@
#define ARCH_HAS_MUTEX_AND_OWN 1

#include <linux/elide.h>
+#include <linux/jump_label.h>

-extern bool mutex_elision;
+extern struct static_key mutex_elision;
+extern struct elision_config mutex_elision_config;

/*
* Try speculation first and only do the normal locking and owner setting
@@ -21,8 +23,10 @@ extern bool mutex_elision;
#define mutex_free(l) (atomic_read(&(l)->count) == 1)

#define __mutex_fastpath_lock_and_own(l, s) ({ \
- if (!elide_lock(mutex_elision, \
- mutex_free(l))) { \
+ if (!elide_lock_adapt(mutex_elision, \
+ mutex_free(l), \
+ &l->elision_adapt, \
+ &mutex_elision_config)) { \
__mutex_fastpath_lock(&(l)->count, s); \
mutex_set_owner(l); \
} \
@@ -37,7 +41,10 @@ extern bool mutex_elision;

#define __mutex_fastpath_lock_retval_and_own(l, s) ({ \
int ret = 0; \
- if (!elide_lock(mutex_elision, mutex_free(l))) { \
+ if (!elide_lock_adapt(mutex_elision, \
+ mutex_free(l), \
+ &l->elision_adapt, \
+ &mutex_elision_config)) { \
ret = __mutex_fastpath_lock_retval(&(l)->count, s); \
if (!ret) \
mutex_set_owner(l); \
@@ -46,7 +53,10 @@ extern bool mutex_elision;

#define __mutex_fastpath_trylock_and_own(l, s) ({ \
int ret = 1; \
- if (!elide_lock(mutex_elision, mutex_free(l))) {\
+ if (!elide_lock_adapt(mutex_elision, \
+ mutex_free(l), \
+ &l->elision_adapt, \
+ &mutex_elision_config)) { \
ret = __mutex_fastpath_trylock(&(l)->count, s); \
if (ret) \
mutex_set_owner(l); \
diff --git a/arch/x86/kernel/rtm-locks.c b/arch/x86/kernel/rtm-locks.c
index 8d4763d..a313a81 100644
--- a/arch/x86/kernel/rtm-locks.c
+++ b/arch/x86/kernel/rtm-locks.c
@@ -416,6 +416,9 @@ static unsigned rtm_patch(u8 type, u16 clobbers, void *ibuf,
}
}

+struct static_key mutex_elision = STATIC_KEY_INIT_FALSE;
+module_param(mutex_elision, static_key, 0644);
+
void init_rtm_spinlocks(void)
{
if (!boot_cpu_has(X86_FEATURE_RTM))
@@ -441,10 +444,13 @@ void init_rtm_spinlocks(void)
pv_irq_ops.irq_enable = PV_CALLEE_SAVE(rtm_irq_enable);
pv_irq_ops.restore_fl = PV_CALLEE_SAVE(rtm_restore_fl);
pv_init_ops.patch = rtm_patch;
+
+ static_key_slow_inc(&mutex_elision);
}

-__read_mostly bool mutex_elision = true;
-module_param(mutex_elision, bool, 0644);
+__read_mostly struct elision_config mutex_elision_config =
+ DEFAULT_ELISION_CONFIG;
+TUNE_ELISION_CONFIG(mutex, mutex_elision_config);

__read_mostly bool rwsem_elision = true;
module_param(rwsem_elision, bool, 0644);
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 0574095..7ae9a08 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -54,6 +54,9 @@ struct mutex {
#if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP)
struct task_struct *owner;
#endif
+#ifdef CONFIG_RTM_LOCKS
+ short elision_adapt;
+#endif
#ifdef CONFIG_DEBUG_MUTEXES
const char *name;
void *magic;
--
1.7.7.6