Jeremy Fitzhardinge
2010-Jul-13 22:14 UTC
[Xen-devel] [PATCH RFC 06/12] x86/ticketlock: make __ticket_spin_trylock common
Make trylock code common regardless of ticket size.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
---
arch/x86/include/asm/spinlock.h | 55 +++++++++-----------------------
arch/x86/include/asm/spinlock_types.h | 3 ++
2 files changed, 19 insertions(+), 39 deletions(-)
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index 4f9fa24..507f83c 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -100,48 +100,25 @@ static __always_inline void __ticket_spin_lock(struct
arch_spinlock *lock)
barrier(); /* make sure nothing creeps before the lock is taken */
}
-#if (NR_CPUS < 256)
static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
{
- unsigned int tmp, new;
-
- asm volatile("movzwl %2, %0\n\t"
- "cmpb %h0,%b0\n\t"
- "leal 0x100(%" REG_PTR_MODE "0), %1\n\t"
- "jne 1f\n\t"
- LOCK_PREFIX "cmpxchgw %w1,%2\n\t"
- "1:"
- "sete %b1\n\t"
- "movzbl %b1,%0\n\t"
- : "=&a" (tmp), "=&q" (new), "+m"
(lock->slock)
- :
- : "memory", "cc");
-
- return tmp;
-}
-#else
-static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
-{
- unsigned tmp;
- unsigned new;
-
- asm volatile("movl %2,%0\n\t"
- "movl %0,%1\n\t"
- "roll $16, %0\n\t"
- "cmpl %0,%1\n\t"
- "leal 0x00010000(%" REG_PTR_MODE "0), %1\n\t"
- "jne 1f\n\t"
- LOCK_PREFIX "cmpxchgl %1,%2\n\t"
- "1:"
- "sete %b1\n\t"
- "movzbl %b1,%0\n\t"
- : "=&a" (tmp), "=&q" (new), "+m"
(lock->slock)
- :
- : "memory", "cc");
-
- return tmp;
+ union {
+ struct __raw_tickets tickets;
+ __ticketpair_t slock;
+ } tmp, new;
+ int ret;
+
+ tmp.tickets = ACCESS_ONCE(lock->tickets);
+ if (tmp.tickets.head != tmp.tickets.tail)
+ return 0;
+
+ new.slock = tmp.slock + (1 << TICKET_SHIFT);
+
+ ret = cmpxchg(&lock->ticketpair, tmp.slock, new.slock) == tmp.slock;
+ barrier(); /* just make nothing creeps before lock is claimed */
+
+ return ret;
}
-#endif
static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
{
diff --git a/arch/x86/include/asm/spinlock_types.h
b/arch/x86/include/asm/spinlock_types.h
index 4582640..48dafc3 100644
--- a/arch/x86/include/asm/spinlock_types.h
+++ b/arch/x86/include/asm/spinlock_types.h
@@ -9,8 +9,10 @@
#if (CONFIG_NR_CPUS < 256)
typedef u8 __ticket_t;
+typedef u16 __ticketpair_t;
#else
typedef u16 __ticket_t;
+typedef u32 __ticketpair_t;
#endif
#define TICKET_SHIFT (sizeof(__ticket_t) * 8)
@@ -19,6 +21,7 @@ typedef u16 __ticket_t;
typedef struct arch_spinlock {
union {
unsigned int slock;
+ __ticketpair_t ticketpair;
struct __raw_tickets {
__ticket_t head, tail;
} tickets;
--
1.7.1.1
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