x86, ticketlock: Clean up types and accessors
A few cleanups to the way spinlocks are defined and accessed:
- define __ticket_t which is the size of a spinlock ticket (ie, enough
bits to hold all the cpus)
- Define struct arch_spinlock as a union containing plain slock and
the head and tail tickets
- Use head and tail to implement some of the spinlock predicates.
- Make all ticket variables unsigned.
- Use TICKET_SHIFT to form constants
Most of this will be used in later patches.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Link: http://lkml.kernel.org/r/4E5BCC40.3030501@goop.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
index ee67edf..ea2a04f 100644
--- a/arch/x86/include/asm/spinlock.h
+++ b/arch/x86/include/asm/spinlock.h
@@ -55,11 +55,9 @@
* much between them in performance though, especially as locks are out of line.
*/
#if (NR_CPUS < 256)
-#define TICKET_SHIFT 8
-
static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
{
- short inc = 0x0100;
+ unsigned short inc = 1 << TICKET_SHIFT;
asm volatile (
LOCK_PREFIX "xaddw %w0, %1\n"
@@ -78,7 +76,7 @@
static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
{
- int tmp, new;
+ unsigned int tmp, new;
asm volatile("movzwl %2, %0\n\t"
"cmpb %h0,%b0\n\t"
@@ -103,12 +101,10 @@
: "memory", "cc");
}
#else
-#define TICKET_SHIFT 16
-
static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
{
- int inc = 0x00010000;
- int tmp;
+ unsigned inc = 1 << TICKET_SHIFT;
+ unsigned tmp;
asm volatile(LOCK_PREFIX "xaddl %0, %1\n"
"movzwl %w0, %2\n\t"
@@ -128,8 +124,8 @@
static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
{
- int tmp;
- int new;
+ unsigned tmp;
+ unsigned new;
asm volatile("movl %2,%0\n\t"
"movl %0,%1\n\t"
@@ -159,16 +155,16 @@
static inline int __ticket_spin_is_locked(arch_spinlock_t *lock)
{
- int tmp = ACCESS_ONCE(lock->slock);
+ struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets);
- return !!(((tmp >> TICKET_SHIFT) ^ tmp) & ((1 << TICKET_SHIFT) - 1));
+ return !!(tmp.tail ^ tmp.head);
}
static inline int __ticket_spin_is_contended(arch_spinlock_t *lock)
{
- int tmp = ACCESS_ONCE(lock->slock);
+ struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets);
- return (((tmp >> TICKET_SHIFT) - tmp) & ((1 << TICKET_SHIFT) - 1)) > 1;
+ return ((tmp.tail - tmp.head) & TICKET_MASK) > 1;
}
#ifndef CONFIG_PARAVIRT_SPINLOCKS