#define __raw_spin_lock_init(x) ((x)->lock = 0)
-#ifdef ASM_SUPPORTED
/*
- * Try to get the lock. If we fail to get the lock, make a non-standard call to
- * ia64_spinlock_contention(). We do not use a normal call because that would force all
- * callers of __raw_spin_lock() to be non-leaf routines. Instead, ia64_spinlock_contention() is
- * carefully coded to touch only those registers that __raw_spin_lock() marks "clobbered".
+ * Ticket locks are conceptually two parts, one indicating the current head of
+ * the queue, and the other indicating the current tail. The lock is acquired
+ * by atomically noting the tail and incrementing it by one (thus adding
+ * ourself to the queue and noting our position), then waiting until the head
+ * becomes equal to the the initial value of the tail.
+ *
+ * 63 32 31 0
+ * +----------------------------------------------------+
+ * | next_ticket_number | now_serving |
+ * +----------------------------------------------------+
*/
-#define IA64_SPINLOCK_CLOBBERS "ar.ccv", "ar.pfs", "p14", "p15", "r27", "r28", "r29", "r30", "b6", "memory"
+#define TICKET_SHIFT 32
-static inline void
-__raw_spin_lock_flags (raw_spinlock_t *lock, unsigned long flags)
+static __always_inline void __ticket_spin_lock(raw_spinlock_t *lock)
{
- register volatile unsigned int *ptr asm ("r31") = &lock->lock;
-
-#if (__GNUC__ == 3 && __GNUC_MINOR__ < 3)
-# ifdef CONFIG_ITANIUM
- /* don't use brl on Itanium... */
- asm volatile ("{\n\t"
- " mov ar.ccv = r0\n\t"
- " mov r28 = ip\n\t"
- " mov r30 = 1;;\n\t"
- "}\n\t"
- "cmpxchg4.acq r30 = [%1], r30, ar.ccv\n\t"
- "movl r29 = ia64_spinlock_contention_pre3_4;;\n\t"
- "cmp4.ne p14, p0 = r30, r0\n\t"
- "mov b6 = r29;;\n\t"
- "mov r27=%2\n\t"
- "(p14) br.cond.spnt.many b6"
- : "=r"(ptr) : "r"(ptr), "r" (flags) : IA64_SPINLOCK_CLOBBERS);
-# else
- asm volatile ("{\n\t"
- " mov ar.ccv = r0\n\t"
- " mov r28 = ip\n\t"
- " mov r30 = 1;;\n\t"
- "}\n\t"
- "cmpxchg4.acq r30 = [%1], r30, ar.ccv;;\n\t"
- "cmp4.ne p14, p0 = r30, r0\n\t"
- "mov r27=%2\n\t"
- "(p14) brl.cond.spnt.many ia64_spinlock_contention_pre3_4;;"
- : "=r"(ptr) : "r"(ptr), "r" (flags) : IA64_SPINLOCK_CLOBBERS);
-# endif /* CONFIG_MCKINLEY */
-#else
-# ifdef CONFIG_ITANIUM
- /* don't use brl on Itanium... */
- /* mis-declare, so we get the entry-point, not it's function descriptor: */
- asm volatile ("mov r30 = 1\n\t"
- "mov r27=%2\n\t"
- "mov ar.ccv = r0;;\n\t"
- "cmpxchg4.acq r30 = [%0], r30, ar.ccv\n\t"
- "movl r29 = ia64_spinlock_contention;;\n\t"
- "cmp4.ne p14, p0 = r30, r0\n\t"
- "mov b6 = r29;;\n\t"
- "(p14) br.call.spnt.many b6 = b6"
- : "=r"(ptr) : "r"(ptr), "r" (flags) : IA64_SPINLOCK_CLOBBERS);
-# else
- asm volatile ("mov r30 = 1\n\t"
- "mov r27=%2\n\t"
- "mov ar.ccv = r0;;\n\t"
- "cmpxchg4.acq r30 = [%0], r30, ar.ccv;;\n\t"
- "cmp4.ne p14, p0 = r30, r0\n\t"
- "(p14) brl.call.spnt.many b6=ia64_spinlock_contention;;"
- : "=r"(ptr) : "r"(ptr), "r" (flags) : IA64_SPINLOCK_CLOBBERS);
-# endif /* CONFIG_MCKINLEY */
-#endif
+ int *p = (int *)&lock->lock, turn, now_serving;
+
+ now_serving = *p;
+ turn = ia64_fetchadd(1, p+1, acq);
+
+ if (turn == now_serving)
+ return;
+
+ do {
+ cpu_relax();
+ } while (ACCESS_ONCE(*p) != turn);
}
-#define __raw_spin_lock(lock) __raw_spin_lock_flags(lock, 0)
+static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock)
+{
+ long tmp = ACCESS_ONCE(lock->lock), try;
-/* Unlock by doing an ordered store and releasing the cacheline with nta */
-static inline void __raw_spin_unlock(raw_spinlock_t *x) {
- barrier();
- asm volatile ("st4.rel.nta [%0] = r0\n\t" :: "r"(x));
+ if (!(((tmp >> TICKET_SHIFT) ^ tmp) & ((1L << TICKET_SHIFT) - 1))) {
+ try = tmp + (1L << TICKET_SHIFT);
+
+ return ia64_cmpxchg(acq, &lock->lock, tmp, try, sizeof (tmp)) == tmp;
+ }
+ return 0;
}
-#else /* !ASM_SUPPORTED */
-#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
-# define __raw_spin_lock(x) \
-do { \
- __u32 *ia64_spinlock_ptr = (__u32 *) (x); \
- __u64 ia64_spinlock_val; \
- ia64_spinlock_val = ia64_cmpxchg4_acq(ia64_spinlock_ptr, 1, 0); \
- if (unlikely(ia64_spinlock_val)) { \
- do { \
- while (*ia64_spinlock_ptr) \
- ia64_barrier(); \
- ia64_spinlock_val = ia64_cmpxchg4_acq(ia64_spinlock_ptr, 1, 0); \
- } while (ia64_spinlock_val); \
- } \
-} while (0)
-#define __raw_spin_unlock(x) do { barrier(); ((raw_spinlock_t *) x)->lock = 0; } while (0)
-#endif /* !ASM_SUPPORTED */
+static __always_inline void __ticket_spin_unlock(raw_spinlock_t *lock)
+{
+ int *p = (int *)&lock->lock;
+
+ (void)ia64_fetchadd(1, p, rel);
+}
+
+static inline int __ticket_spin_is_locked(raw_spinlock_t *lock)
+{
+ long tmp = ACCESS_ONCE(lock->lock);
+
+ return !!(((tmp >> TICKET_SHIFT) ^ tmp) & ((1L << TICKET_SHIFT) - 1));
+}
+
+static inline int __ticket_spin_is_contended(raw_spinlock_t *lock)
+{
+ long tmp = ACCESS_ONCE(lock->lock);
-#define __raw_spin_is_locked(x) ((x)->lock != 0)
-#define __raw_spin_trylock(x) (cmpxchg_acq(&(x)->lock, 0, 1) == 0)
-#define __raw_spin_unlock_wait(lock) \
- do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
+ return (((tmp >> TICKET_SHIFT) - tmp) & ((1L << TICKET_SHIFT) - 1)) > 1;
+}
+
+static inline int __raw_spin_is_locked(raw_spinlock_t *lock)
+{
+ return __ticket_spin_is_locked(lock);
+}
+
+static inline int __raw_spin_is_contended(raw_spinlock_t *lock)
+{
+ return __ticket_spin_is_contended(lock);
+}
+#define __raw_spin_is_contended __raw_spin_is_contended
+
+static __always_inline void __raw_spin_lock(raw_spinlock_t *lock)
+{
+ __ticket_spin_lock(lock);
+}
+
+static __always_inline int __raw_spin_trylock(raw_spinlock_t *lock)
+{
+ return __ticket_spin_trylock(lock);
+}
+
+static __always_inline void __raw_spin_unlock(raw_spinlock_t *lock)
+{
+ __ticket_spin_unlock(lock);
+}
+
+static __always_inline void __raw_spin_lock_flags(raw_spinlock_t *lock,
+ unsigned long flags)
+{
+ __raw_spin_lock(lock);
+}
+
+static inline void __raw_spin_unlock_wait(raw_spinlock_t *lock)
+{
+ while (__raw_spin_is_locked(lock))
+ cpu_relax();
+}
#define __raw_read_can_lock(rw) (*(volatile int *)(rw) >= 0)
#define __raw_write_can_lock(rw) (*(volatile int *)(rw) == 0)
#endif /* CONFIG_IA64_BRL_EMU */
#ifdef CONFIG_SMP
- /*
- * This routine handles spinlock contention. It uses a non-standard calling
- * convention to avoid converting leaf routines into interior routines. Because
- * of this special convention, there are several restrictions:
- *
- * - do not use gp relative variables, this code is called from the kernel
- * and from modules, r1 is undefined.
- * - do not use stacked registers, the caller owns them.
- * - do not use the scratch stack space, the caller owns it.
- * - do not use any registers other than the ones listed below
- *
- * Inputs:
- * ar.pfs - saved CFM of caller
- * ar.ccv - 0 (and available for use)
- * r27 - flags from spin_lock_irqsave or 0. Must be preserved.
- * r28 - available for use.
- * r29 - available for use.
- * r30 - available for use.
- * r31 - address of lock, available for use.
- * b6 - return address
- * p14 - available for use.
- * p15 - used to track flag status.
- *
- * If you patch this code to use more registers, do not forget to update
- * the clobber lists for spin_lock() in arch/ia64/include/asm/spinlock.h.
- */
-
-#if (__GNUC__ == 3 && __GNUC_MINOR__ < 3)
-
-GLOBAL_ENTRY(ia64_spinlock_contention_pre3_4)
- .prologue
- .save ar.pfs, r0 // this code effectively has a zero frame size
- .save rp, r28
- .body
- nop 0
- tbit.nz p15,p0=r27,IA64_PSR_I_BIT
- .restore sp // pop existing prologue after next insn
- mov b6 = r28
- .prologue
- .save ar.pfs, r0
- .altrp b6
- .body
- ;;
-(p15) ssm psr.i // reenable interrupts if they were on
- // DavidM says that srlz.d is slow and is not required in this case
-.wait:
- // exponential backoff, kdb, lockmeter etc. go in here
- hint @pause
- ld4 r30=[r31] // don't use ld4.bias; if it's contended, we won't write the word
- nop 0
- ;;
- cmp4.ne p14,p0=r30,r0
-(p14) br.cond.sptk.few .wait
-(p15) rsm psr.i // disable interrupts if we reenabled them
- br.cond.sptk.few b6 // lock is now free, try to acquire
- .global ia64_spinlock_contention_pre3_4_end // for kernprof
-ia64_spinlock_contention_pre3_4_end:
-END(ia64_spinlock_contention_pre3_4)
-
-#else
-
-GLOBAL_ENTRY(ia64_spinlock_contention)
- .prologue
- .altrp b6
- .body
- tbit.nz p15,p0=r27,IA64_PSR_I_BIT
- ;;
-.wait:
-(p15) ssm psr.i // reenable interrupts if they were on
- // DavidM says that srlz.d is slow and is not required in this case
-.wait2:
- // exponential backoff, kdb, lockmeter etc. go in here
- hint @pause
- ld4 r30=[r31] // don't use ld4.bias; if it's contended, we won't write the word
- ;;
- cmp4.ne p14,p0=r30,r0
- mov r30 = 1
-(p14) br.cond.sptk.few .wait2
-(p15) rsm psr.i // disable interrupts if we reenabled them
- ;;
- cmpxchg4.acq r30=[r31], r30, ar.ccv
- ;;
- cmp4.ne p14,p0=r0,r30
-(p14) br.cond.sptk.few .wait
-
- br.ret.sptk.many b6 // lock is now taken
-END(ia64_spinlock_contention)
-
-#endif
#ifdef CONFIG_HOTPLUG_CPU
GLOBAL_ENTRY(ia64_jump_to_sal)
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