1 files changed, 290 insertions, 0 deletions
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
new file mode 100644
index 00000000000..54f1c8068c0
--- /dev/null
+++ b/arch/x86/include/asm/spinlock.h
@@ -0,0 +1,290 @@
+#ifndef _ASM_X86_SPINLOCK_H
+#define _ASM_X86_SPINLOCK_H
+
+#include <linux/jump_label.h>
+#include <linux/atomic.h>
+#include <asm/page.h>
+#include <asm/processor.h>
+#include <linux/compiler.h>
+#include <asm/paravirt.h>
+#include <asm/bitops.h>
+
+/*
+ * Your basic SMP spinlocks, allowing only a single CPU anywhere
+ *
+ * Simple spin lock operations.  There are two variants, one clears IRQ's
+ * on the local processor, one does not.
+ *
+ * These are fair FIFO ticket locks, which support up to 2^16 CPUs.
+ *
+ * (the type definitions are in asm/spinlock_types.h)
+ */
+
+#ifdef CONFIG_X86_32
+# define LOCK_PTR_REG "a"
+#else
+# define LOCK_PTR_REG "D"
+#endif
+
+#if defined(CONFIG_X86_32) && (defined(CONFIG_X86_PPRO_FENCE))
+/*
+ * On PPro SMP, we use a locked operation to unlock
+ * (PPro errata 66, 92)
+ */
+# define UNLOCK_LOCK_PREFIX LOCK_PREFIX
+#else
+# define UNLOCK_LOCK_PREFIX
+#endif
+
+/* How long a lock should spin before we consider blocking */
+#define SPIN_THRESHOLD	(1 << 15)
+
+extern struct static_key paravirt_ticketlocks_enabled;
+static __always_inline bool static_key_false(struct static_key *key);
+
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+
+static inline void __ticket_enter_slowpath(arch_spinlock_t *lock)
+{
+	set_bit(0, (volatile unsigned long *)&lock->tickets.tail);
+}
+
+#else  /* !CONFIG_PARAVIRT_SPINLOCKS */
+static __always_inline void __ticket_lock_spinning(arch_spinlock_t *lock,
+							__ticket_t ticket)
+{
+}
+static inline void __ticket_unlock_kick(arch_spinlock_t *lock,
+							__ticket_t ticket)
+{
+}
+
+#endif /* CONFIG_PARAVIRT_SPINLOCKS */
+
+static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
+{
+	return lock.tickets.head == lock.tickets.tail;
+}
+
+/*
+ * 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.
+ *
+ * We use an xadd covering *both* parts of the lock, to increment the tail and
+ * also load the position of the head, which takes care of memory ordering
+ * issues and should be optimal for the uncontended case. Note the tail must be
+ * in the high part, because a wide xadd increment of the low part would carry
+ * up and contaminate the high part.
+ */
+static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
+{
+	register struct __raw_tickets inc = { .tail = TICKET_LOCK_INC };
+
+	inc = xadd(&lock->tickets, inc);
+	if (likely(inc.head == inc.tail))
+		goto out;
+
+	inc.tail &= ~TICKET_SLOWPATH_FLAG;
+	for (;;) {
+		unsigned count = SPIN_THRESHOLD;
+
+		do {
+			if (ACCESS_ONCE(lock->tickets.head) == inc.tail)
+				goto out;
+			cpu_relax();
+		} while (--count);
+		__ticket_lock_spinning(lock, inc.tail);
+	}
+out:	barrier();	/* make sure nothing creeps before the lock is taken */
+}
+
+static __always_inline int arch_spin_trylock(arch_spinlock_t *lock)
+{
+	arch_spinlock_t old, new;
+
+	old.tickets = ACCESS_ONCE(lock->tickets);
+	if (old.tickets.head != (old.tickets.tail & ~TICKET_SLOWPATH_FLAG))
+		return 0;
+
+	new.head_tail = old.head_tail + (TICKET_LOCK_INC << TICKET_SHIFT);
+
+	/* cmpxchg is a full barrier, so nothing can move before it */
+	return cmpxchg(&lock->head_tail, old.head_tail, new.head_tail) == old.head_tail;
+}
+
+static inline void __ticket_unlock_slowpath(arch_spinlock_t *lock,
+					    arch_spinlock_t old)
+{
+	arch_spinlock_t new;
+
+	BUILD_BUG_ON(((__ticket_t)NR_CPUS) != NR_CPUS);
+
+	/* Perform the unlock on the "before" copy */
+	old.tickets.head += TICKET_LOCK_INC;
+
+	/* Clear the slowpath flag */
+	new.head_tail = old.head_tail & ~(TICKET_SLOWPATH_FLAG << TICKET_SHIFT);
+
+	/*
+	 * If the lock is uncontended, clear the flag - use cmpxchg in
+	 * case it changes behind our back though.
+	 */
+	if (new.tickets.head != new.tickets.tail ||
+	    cmpxchg(&lock->head_tail, old.head_tail,
+					new.head_tail) != old.head_tail) {
+		/*
+		 * Lock still has someone queued for it, so wake up an
+		 * appropriate waiter.
+		 */
+		__ticket_unlock_kick(lock, old.tickets.head);
+	}
+}
+
+static __always_inline void arch_spin_unlock(arch_spinlock_t *lock)
+{
+	if (TICKET_SLOWPATH_FLAG &&
+	    static_key_false(&paravirt_ticketlocks_enabled)) {
+		arch_spinlock_t prev;
+
+		prev = *lock;
+		add_smp(&lock->tickets.head, TICKET_LOCK_INC);
+
+		/* add_smp() is a full mb() */
+
+		if (unlikely(lock->tickets.tail & TICKET_SLOWPATH_FLAG))
+			__ticket_unlock_slowpath(lock, prev);
+	} else
+		__add(&lock->tickets.head, TICKET_LOCK_INC, UNLOCK_LOCK_PREFIX);
+}
+
+static inline int arch_spin_is_locked(arch_spinlock_t *lock)
+{
+	struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets);
+
+	return tmp.tail != tmp.head;
+}
+
+static inline int arch_spin_is_contended(arch_spinlock_t *lock)
+{
+	struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets);
+
+	return (__ticket_t)(tmp.tail - tmp.head) > TICKET_LOCK_INC;
+}
+#define arch_spin_is_contended	arch_spin_is_contended
+
+static __always_inline void arch_spin_lock_flags(arch_spinlock_t *lock,
+						  unsigned long flags)
+{
+	arch_spin_lock(lock);
+}
+
+static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
+{
+	while (arch_spin_is_locked(lock))
+		cpu_relax();
+}
+
+#ifndef CONFIG_QUEUE_RWLOCK
+/*
+ * Read-write spinlocks, allowing multiple readers
+ * but only one writer.
+ *
+ * NOTE! it is quite common to have readers in interrupts
+ * but no interrupt writers. For those circumstances we
+ * can "mix" irq-safe locks - any writer needs to get a
+ * irq-safe write-lock, but readers can get non-irqsafe
+ * read-locks.
+ *
+ * On x86, we implement read-write locks as a 32-bit counter
+ * with the high bit (sign) being the "contended" bit.
+ */
+
+/**
+ * read_can_lock - would read_trylock() succeed?
+ * @lock: the rwlock in question.
+ */
+static inline int arch_read_can_lock(arch_rwlock_t *lock)
+{
+	return lock->lock > 0;
+}
+
+/**
+ * write_can_lock - would write_trylock() succeed?
+ * @lock: the rwlock in question.
+ */
+static inline int arch_write_can_lock(arch_rwlock_t *lock)
+{
+	return lock->write == WRITE_LOCK_CMP;
+}
+
+static inline void arch_read_lock(arch_rwlock_t *rw)
+{
+	asm volatile(LOCK_PREFIX READ_LOCK_SIZE(dec) " (%0)\n\t"
+		     "jns 1f\n"
+		     "call __read_lock_failed\n\t"
+		     "1:\n"
+		     ::LOCK_PTR_REG (rw) : "memory");
+}
+
+static inline void arch_write_lock(arch_rwlock_t *rw)
+{
+	asm volatile(LOCK_PREFIX WRITE_LOCK_SUB(%1) "(%0)\n\t"
+		     "jz 1f\n"
+		     "call __write_lock_failed\n\t"
+		     "1:\n"
+		     ::LOCK_PTR_REG (&rw->write), "i" (RW_LOCK_BIAS)
+		     : "memory");
+}
+
+static inline int arch_read_trylock(arch_rwlock_t *lock)
+{
+	READ_LOCK_ATOMIC(t) *count = (READ_LOCK_ATOMIC(t) *)lock;
+
+	if (READ_LOCK_ATOMIC(dec_return)(count) >= 0)
+		return 1;
+	READ_LOCK_ATOMIC(inc)(count);
+	return 0;
+}
+
+static inline int arch_write_trylock(arch_rwlock_t *lock)
+{
+	atomic_t *count = (atomic_t *)&lock->write;
+
+	if (atomic_sub_and_test(WRITE_LOCK_CMP, count))
+		return 1;
+	atomic_add(WRITE_LOCK_CMP, count);
+	return 0;
+}
+
+static inline void arch_read_unlock(arch_rwlock_t *rw)
+{
+	asm volatile(LOCK_PREFIX READ_LOCK_SIZE(inc) " %0"
+		     :"+m" (rw->lock) : : "memory");
+}
+
+static inline void arch_write_unlock(arch_rwlock_t *rw)
+{
+	asm volatile(LOCK_PREFIX WRITE_LOCK_ADD(%1) "%0"
+		     : "+m" (rw->write) : "i" (RW_LOCK_BIAS) : "memory");
+}
+#else
+#include <asm/qrwlock.h>
+#endif /* CONFIG_QUEUE_RWLOCK */
+
+#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
+#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
+
+#undef READ_LOCK_SIZE
+#undef READ_LOCK_ATOMIC
+#undef WRITE_LOCK_ADD
+#undef WRITE_LOCK_SUB
+#undef WRITE_LOCK_CMP
+
+#define arch_spin_relax(lock)	cpu_relax()
+#define arch_read_relax(lock)	cpu_relax()
+#define arch_write_relax(lock)	cpu_relax()
+
+#endif /* _ASM_X86_SPINLOCK_H */