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Date: Mon, 12 Jan 2009 12:53:45 +0100 (CET)
From: Jiri Kosina <jkosina@...e.cz>
To: Ingo Molnar <mingo@...e.hu>,
Jeremy Fitzhardinge <jeremy@...source.com>
cc: linux-kernel@...r.kernel.org
Subject: [PATCH] x86: remove byte locks
Remove byte locks implementation, which was introduced by Jeremy in
8efcbab6 ("paravirt: introduce a "lock-byte" spinlock implementation"),
but turned out to be dead code that is not used by any in-kernel
virtualization guest (Xen uses its own variant of spinlocks implementation
and KVM is not planning to move to byte locks).
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
---
arch/x86/include/asm/paravirt.h | 2 -
arch/x86/include/asm/spinlock.h | 66 +--------------------------------
arch/x86/kernel/paravirt-spinlocks.c | 10 -----
3 files changed, 2 insertions(+), 76 deletions(-)
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index ba3e2ff..32bc6c2 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -1389,8 +1389,6 @@ static inline void __set_fixmap(unsigned /* enum fixed_addresses */ idx,
void _paravirt_nop(void);
#define paravirt_nop ((void *)_paravirt_nop)
-void paravirt_use_bytelocks(void);
-
#ifdef CONFIG_SMP
static inline int __raw_spin_is_locked(struct raw_spinlock *lock)
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index d17c919..2bd6b11 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -172,70 +172,8 @@ static inline int __ticket_spin_is_contended(raw_spinlock_t *lock)
return (((tmp >> TICKET_SHIFT) - tmp) & ((1 << TICKET_SHIFT) - 1)) > 1;
}
-#ifdef CONFIG_PARAVIRT
-/*
- * Define virtualization-friendly old-style lock byte lock, for use in
- * pv_lock_ops if desired.
- *
- * This differs from the pre-2.6.24 spinlock by always using xchgb
- * rather than decb to take the lock; this allows it to use a
- * zero-initialized lock structure. It also maintains a 1-byte
- * contention counter, so that we can implement
- * __byte_spin_is_contended.
- */
-struct __byte_spinlock {
- s8 lock;
- s8 spinners;
-};
-
-static inline int __byte_spin_is_locked(raw_spinlock_t *lock)
-{
- struct __byte_spinlock *bl = (struct __byte_spinlock *)lock;
- return bl->lock != 0;
-}
-
-static inline int __byte_spin_is_contended(raw_spinlock_t *lock)
-{
- struct __byte_spinlock *bl = (struct __byte_spinlock *)lock;
- return bl->spinners != 0;
-}
-
-static inline void __byte_spin_lock(raw_spinlock_t *lock)
-{
- struct __byte_spinlock *bl = (struct __byte_spinlock *)lock;
- s8 val = 1;
-
- asm("1: xchgb %1, %0\n"
- " test %1,%1\n"
- " jz 3f\n"
- " " LOCK_PREFIX "incb %2\n"
- "2: rep;nop\n"
- " cmpb $1, %0\n"
- " je 2b\n"
- " " LOCK_PREFIX "decb %2\n"
- " jmp 1b\n"
- "3:"
- : "+m" (bl->lock), "+q" (val), "+m" (bl->spinners): : "memory");
-}
-
-static inline int __byte_spin_trylock(raw_spinlock_t *lock)
-{
- struct __byte_spinlock *bl = (struct __byte_spinlock *)lock;
- u8 old = 1;
-
- asm("xchgb %1,%0"
- : "+m" (bl->lock), "+q" (old) : : "memory");
+#ifndef CONFIG_PARAVIRT
- return old == 0;
-}
-
-static inline void __byte_spin_unlock(raw_spinlock_t *lock)
-{
- struct __byte_spinlock *bl = (struct __byte_spinlock *)lock;
- smp_wmb();
- bl->lock = 0;
-}
-#else /* !CONFIG_PARAVIRT */
static inline int __raw_spin_is_locked(raw_spinlock_t *lock)
{
return __ticket_spin_is_locked(lock);
@@ -267,7 +205,7 @@ static __always_inline void __raw_spin_lock_flags(raw_spinlock_t *lock,
__raw_spin_lock(lock);
}
-#endif /* CONFIG_PARAVIRT */
+#endif
static inline void __raw_spin_unlock_wait(raw_spinlock_t *lock)
{
diff --git a/arch/x86/kernel/paravirt-spinlocks.c b/arch/x86/kernel/paravirt-spinlocks.c
index 95777b0..3a7c5a4 100644
--- a/arch/x86/kernel/paravirt-spinlocks.c
+++ b/arch/x86/kernel/paravirt-spinlocks.c
@@ -26,13 +26,3 @@ struct pv_lock_ops pv_lock_ops = {
};
EXPORT_SYMBOL(pv_lock_ops);
-void __init paravirt_use_bytelocks(void)
-{
-#ifdef CONFIG_SMP
- pv_lock_ops.spin_is_locked = __byte_spin_is_locked;
- pv_lock_ops.spin_is_contended = __byte_spin_is_contended;
- pv_lock_ops.spin_lock = __byte_spin_lock;
- pv_lock_ops.spin_trylock = __byte_spin_trylock;
- pv_lock_ops.spin_unlock = __byte_spin_unlock;
-#endif
-}
--
1.6.0.2
--
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