On a system with shared processors (a physical processor is multiplexed
between several virtual processors), we encode the lock owner into the
lock token in order to avoid unnecessarily spinning on a lock if the
lock holder isn't currently scheduled on a physical processor.
In the current kernel, we unconditionally encode the lock owner into
the lock token for all the ppc64 platforms no matter it is a shared
processor or not. This introduces a new kernel option to distinguish
the platforms which need this hack.
Signed-off-by: Kevin Hao <haoke...@gmail.com>
---
arch/powerpc/Kconfig | 3 +++
arch/powerpc/include/asm/spinlock.h | 12 ++++++++----
arch/powerpc/lib/locks.c | 4 ++--
arch/powerpc/platforms/pseries/Kconfig | 1 +
4 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 9b780e0d2c18..6949d6099d4c 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -303,6 +303,9 @@ config PGTABLE_LEVELS
default 3 if PPC_64K_PAGES
default 4
+config PPC_HAS_LOCK_OWNER
+ bool
+
source "init/Kconfig"
source "kernel/Kconfig.freezer"
diff --git a/arch/powerpc/include/asm/spinlock.h
b/arch/powerpc/include/asm/spinlock.h
index 4dbe072eecbe..38f40ea63a8c 100644
--- a/arch/powerpc/include/asm/spinlock.h
+++ b/arch/powerpc/include/asm/spinlock.h
@@ -30,7 +30,7 @@
#define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */
-#ifdef CONFIG_PPC64
+#ifdef CONFIG_PPC_HAS_LOCK_OWNER
/* use 0x800000yy when locked, where yy == CPU number */
#ifdef __BIG_ENDIAN__
#define LOCK_TOKEN (*(u32 *)(&get_paca()->lock_token))
@@ -109,7 +109,7 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
* value.
*/
-#if defined(CONFIG_PPC_SPLPAR)
+#if defined(CONFIG_PPC_HAS_LOCK_OWNER)
/* We only yield to the hypervisor if we are in shared processor mode */
#define SHARED_PROCESSOR (lppaca_shared_proc(local_paca->lppaca_ptr))
extern void __spin_yield(arch_spinlock_t *lock);
@@ -164,7 +164,7 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
lock->slock = 0;
}
-#ifdef CONFIG_PPC64
+#ifdef CONFIG_PPC_HAS_LOCK_OWNER
extern void arch_spin_unlock_wait(arch_spinlock_t *lock);
#else
#define arch_spin_unlock_wait(lock) \
@@ -187,9 +187,13 @@ extern void arch_spin_unlock_wait(arch_spinlock_t *lock);
#ifdef CONFIG_PPC64
#define __DO_SIGN_EXTEND "extsw %0,%0\n"
-#define WRLOCK_TOKEN LOCK_TOKEN /* it's negative */
#else
#define __DO_SIGN_EXTEND
+#endif
+
+#ifdef CONFIG_PPC_HAS_LOCK_OWNER
+#define WRLOCK_TOKEN LOCK_TOKEN /* it's negative */
+#else
#define WRLOCK_TOKEN (-1)
#endif
diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c
index 170a0346f756..66513b3e9b0e 100644
--- a/arch/powerpc/lib/locks.c
+++ b/arch/powerpc/lib/locks.c
@@ -19,7 +19,7 @@
#include <linux/smp.h>
/* waiting for a spinlock... */
-#if defined(CONFIG_PPC_SPLPAR)
+#if defined(CONFIG_PPC_HAS_LOCK_OWNER)
#include <asm/hvcall.h>
#include <asm/smp.h>
@@ -66,7 +66,6 @@ void __rw_yield(arch_rwlock_t *rw)
plpar_hcall_norets(H_CONFER,
get_hard_smp_processor_id(holder_cpu), yield_count);
}
-#endif
void arch_spin_unlock_wait(arch_spinlock_t *lock)
{
@@ -83,3 +82,4 @@ void arch_spin_unlock_wait(arch_spinlock_t *lock)
}
EXPORT_SYMBOL(arch_spin_unlock_wait);
+#endif
diff --git a/arch/powerpc/platforms/pseries/Kconfig
b/arch/powerpc/platforms/pseries/Kconfig
index a758a9c3bbba..5402fcc30c3e 100644
--- a/arch/powerpc/platforms/pseries/Kconfig
+++ b/arch/powerpc/platforms/pseries/Kconfig
@@ -27,6 +27,7 @@ config PPC_PSERIES
config PPC_SPLPAR
depends on PPC_PSERIES
bool "Support for shared-processor logical partitions"
+ select PPC_HAS_LOCK_OWNER
default n
help
Enabling this option will make the kernel run more efficiently
--
2.1.0
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