Convert the simple spinlock to ticket-based. This is based on arm64
codes and only cover the systems which doesn't support shared
processors (a physical processor is multiplexed between several
virtual processors).
Signed-off-by: Kevin Hao <haoke...@gmail.com>
---
arch/powerpc/Kconfig | 5 ++
arch/powerpc/include/asm/spinlock.h | 77 ++++++++++++++++++++++++++++++-
arch/powerpc/include/asm/spinlock_types.h | 16 +++++++
3 files changed, 97 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 6949d6099d4c..dff19e522b2d 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -306,6 +306,11 @@ config PGTABLE_LEVELS
config PPC_HAS_LOCK_OWNER
bool
+config PPC_TICKET_LOCK
+ bool
+ depends on !PPC_HAS_LOCK_OWNER
+ default y
+
source "init/Kconfig"
source "kernel/Kconfig.freezer"
diff --git a/arch/powerpc/include/asm/spinlock.h
b/arch/powerpc/include/asm/spinlock.h
index cbc9511df409..40035261d2db 100644
--- a/arch/powerpc/include/asm/spinlock.h
+++ b/arch/powerpc/include/asm/spinlock.h
@@ -59,7 +59,6 @@ extern void __spin_yield(arch_spinlock_t *lock);
extern void __rw_yield(arch_rwlock_t *lock);
extern void arch_spin_unlock_wait(arch_spinlock_t *lock);
#else /* CONFIG_PPC_HAS_LOCK_OWNER */
-#define LOCK_TOKEN 1
#define WRLOCK_TOKEN (-1)
#define SHARED_PROCESSOR 0
#define __spin_yield(x) barrier()
@@ -81,6 +80,77 @@ extern void arch_spin_unlock_wait(arch_spinlock_t *lock);
#define SYNC_IO
#endif
+#ifdef CONFIG_PPC_TICKET_LOCK
+#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
+
+static inline int arch_spin_is_contended(arch_spinlock_t *lock)
+{
+ arch_spinlock_t lockval = READ_ONCE(*lock);
+
+ return (lockval.next - lockval.owner) > 1;
+}
+#define arch_spin_is_contended arch_spin_is_contended
+
+static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
+{
+ return lock.owner == lock.next;
+}
+
+static inline int arch_spin_is_locked(arch_spinlock_t *lock)
+{
+ return !arch_spin_value_unlocked(READ_ONCE(*lock));
+}
+
+static inline unsigned long arch_spin_trylock(arch_spinlock_t *lock)
+{
+ unsigned int tmp;
+ arch_spinlock_t lockval;
+
+ CLEAR_IO_SYNC;
+ __asm__ __volatile__ (
+"1: " PPC_LWARX(%0,0,%2,1) "\n\
+ rotlwi %1,%0,16\n\
+ xor. %1,%1,%0\n\
+ bne- 2f\n\
+ add %0,%0,%3\n\
+ stwcx. %0,0,%2\n\
+ bne- 1b\n"
+ PPC_ACQUIRE_BARRIER
+"2:"
+ : "=&r" (lockval), "=&r" (tmp)
+ : "r" (lock), "r" (1 << TICKET_SHIFT)
+ : "cr0", "memory");
+
+ return !tmp;
+}
+
+static inline void arch_spin_lock(arch_spinlock_t *lock)
+{
+ unsigned int tmp;
+ arch_spinlock_t lockval;
+
+ CLEAR_IO_SYNC;
+ __asm__ __volatile__ (
+"1: " PPC_LWARX(%0,0,%2,1) "\n\
+ add %1,%0,%4\n\
+ stwcx. %1,0,%2\n\
+ bne- 1b\n\
+ rotlwi %1,%0,16\n\
+ cmpw %1,%0\n\
+ beq 3f\n\
+ rlwinm %0,%0,16,16,31\n\
+2: or 1,1,1 # HMT_low\n\
+ lhz %1,0(%3)\n\
+ cmpw %1,%0\n\
+ bne 2b\n\
+ or 2,2,2 # HMT_medium\n\
+3:"
+ PPC_ACQUIRE_BARRIER
+ : "=&r" (lockval), "=&r" (tmp)
+ : "r"(lock), "r" (&lock->owner), "r" (1 << TICKET_SHIFT)
+ : "cr0", "memory");
+}
+#else
static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
{
return lock.slock == 0;
@@ -157,13 +227,18 @@ void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned
long flags)
local_irq_restore(flags_dis);
}
}
+#endif
static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
SYNC_IO;
__asm__ __volatile__("# arch_spin_unlock\n\t"
PPC_RELEASE_BARRIER: : :"memory");
+#ifdef CONFIG_PPC_TICKET_LOCK
+ lock->owner++;
+#else
lock->slock = 0;
+#endif
}
/*
diff --git a/arch/powerpc/include/asm/spinlock_types.h
b/arch/powerpc/include/asm/spinlock_types.h
index 2351adc4fdc4..371770f906dc 100644
--- a/arch/powerpc/include/asm/spinlock_types.h
+++ b/arch/powerpc/include/asm/spinlock_types.h
@@ -5,11 +5,27 @@
# error "please don't include this file directly"
#endif
+#ifdef CONFIG_PPC_TICKET_LOCK
+#define TICKET_SHIFT 16
+
+typedef struct {
+#ifdef __BIG_ENDIAN__
+ u16 next;
+ u16 owner;
+#else
+ u16 owner;
+ u16 next;
+#endif
+} __aligned(4) arch_spinlock_t;
+
+#define __ARCH_SPIN_LOCK_UNLOCKED { 0, 0 }
+#else
typedef struct {
volatile unsigned int slock;
} arch_spinlock_t;
#define __ARCH_SPIN_LOCK_UNLOCKED { 0 }
+#endif /* CONFIG_PPC_TICKET_LOCK */
typedef struct {
volatile signed int lock;
--
2.1.0
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
