redonkable/remarkable-linux
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x86: remove byte locks

Browse source 
Impact: cleanup

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@suse.cz>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jiri Kosina 2009-01-12 12:53:45 +01:00 committed by Ingo Molnar
parent 422e79a8b3
commit afb33f8c0d
3 changed files with 2 additions and 76 deletions
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2
arch/x86/include/asm/paravirt.h
View file

@ -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)

66
arch/x86/include/asm/spinlock.h
View file

@ -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;
};
#ifndef CONFIG_PARAVIRT
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");
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)
{

10
arch/x86/kernel/paravirt-spinlocks.c
View file

@ -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
}