[Xen-devel] [PATCH RFC 05/12] x86/ticketlock: make __ticket_spin_lock common

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Aside from the particular form of the xadd instruction, they're identical.
So factor out the xadd and use common code for the rest.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/include/asm/spinlock.h |   42 ++++++++++++++++++--------------------
 1 files changed, 20 insertions(+), 22 deletions(-)

diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index 7586d7a..4f9fa24 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -69,13 +69,27 @@ static __always_inline void __ticket_unlock_release(struct 
arch_spinlock *lock)
  * save some instructions and make the code more elegant. There really isn't
  * much between them in performance though, especially as locks are out of 
line.
  */
-#if (NR_CPUS < 256)
-static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
+static __always_inline struct __raw_tickets __ticket_spin_claim(struct 
arch_spinlock *lock)
 {
-       register struct __raw_tickets inc = { .tail = 1 };
+       register struct __raw_tickets tickets = { .tail = 1 };
+
+       if (sizeof(lock->tickets.head) == sizeof(u8))
+               asm volatile (LOCK_PREFIX "xaddw %w0, %1\n"
+                             : "+r" (tickets), "+m" (lock->tickets)
+                             : : "memory", "cc");
+       else
+               asm volatile (LOCK_PREFIX "xaddl %0, %1\n"
+                            : "+r" (tickets), "+m" (lock->tickets)
+                            : : "memory", "cc");
 
-       asm volatile (LOCK_PREFIX "xaddw %w0, %1\n"
-                     : "+r" (inc), "+m" (lock->tickets) : : "memory", "cc");
+       return tickets;
+}
+
+static __always_inline void __ticket_spin_lock(struct arch_spinlock *lock)
+{
+       register struct __raw_tickets inc;
+
+       inc = __ticket_spin_claim(lock);
 
        for (;;) {
                if (inc.head == inc.tail)
@@ -86,6 +100,7 @@ static __always_inline void 
__ticket_spin_lock(arch_spinlock_t *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;
@@ -105,23 +120,6 @@ static __always_inline int 
__ticket_spin_trylock(arch_spinlock_t *lock)
        return tmp;
 }
 #else
-static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
-{
-       register struct __raw_tickets inc = { .tickets.tail = 1 };
-
-       asm volatile(LOCK_PREFIX "xaddl %0, %1\n\t"
-                    : "+r" (inc), "+m" (lock->tickets)
-                    : : "memory", "cc");
-
-       for (;;) {
-               if (inc.head == inc.tail)
-                       return;
-               cpu_relax();
-               inc.head = ACCESS_ONCE(lock->tickets.head);
-       }
-       barrier();              /* make sure nothing creeps before the lock is 
taken */
-}
-
 static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
 {
        unsigned tmp;
-- 
1.7.1.1



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