x86, um: ... and asm-x86 move

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 364 insertions, 0 deletions

diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
new file mode 100644
index 000000000000..157ff7fab97a
--- /dev/null
+++ b/arch/x86/include/asm/spinlock.h
@@ -0,0 +1,364 @@
+#ifndef ASM_X86__SPINLOCK_H
+#define ASM_X86__SPINLOCK_H
+
+#include <asm/atomic.h>
+#include <asm/rwlock.h>
+#include <asm/page.h>
+#include <asm/processor.h>
+#include <linux/compiler.h>
+#include <asm/paravirt.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 are currently limited to 256
+ * CPUs.
+ *
+ * (the type definitions are in asm/spinlock_types.h)
+ */
+
+#ifdef CONFIG_X86_32
+# define LOCK_PTR_REG "a"
+# define REG_PTR_MODE "k"
+#else
+# define LOCK_PTR_REG "D"
+# define REG_PTR_MODE "q"
+#endif
+
+#if defined(CONFIG_X86_32) && \
+	(defined(CONFIG_X86_OOSTORE) || defined(CONFIG_X86_PPRO_FENCE))
+/*
+ * On PPro SMP or if we are using OOSTORE, we use a locked operation to unlock
+ * (PPro errata 66, 92)
+ */
+# define UNLOCK_LOCK_PREFIX LOCK_PREFIX
+#else
+# define UNLOCK_LOCK_PREFIX
+#endif
+
+/*
+ * 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.
+ *
+ * With fewer than 2^8 possible CPUs, we can use x86's partial registers to
+ * 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)
+#define TICKET_SHIFT 8
+
+static __always_inline void __ticket_spin_lock(raw_spinlock_t *lock)
+{
+	short inc = 0x0100;
+
+	asm volatile (
+		LOCK_PREFIX "xaddw %w0, %1\n"
+		"1:\t"
+		"cmpb %h0, %b0\n\t"
+		"je 2f\n\t"
+		"rep ; nop\n\t"
+		"movb %1, %b0\n\t"
+		/* don't need lfence here, because loads are in-order */
+		"jmp 1b\n"
+		"2:"
+		: "+Q" (inc), "+m" (lock->slock)
+		:
+		: "memory", "cc");
+}
+
+static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock)
+{
+	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;
+}
+
+static __always_inline void __ticket_spin_unlock(raw_spinlock_t *lock)
+{
+	asm volatile(UNLOCK_LOCK_PREFIX "incb %0"
+		     : "+m" (lock->slock)
+		     :
+		     : "memory", "cc");
+}
+#else
+#define TICKET_SHIFT 16
+
+static __always_inline void __ticket_spin_lock(raw_spinlock_t *lock)
+{
+	int inc = 0x00010000;
+	int tmp;
+
+	asm volatile(LOCK_PREFIX "xaddl %0, %1\n"
+		     "movzwl %w0, %2\n\t"
+		     "shrl $16, %0\n\t"
+		     "1:\t"
+		     "cmpl %0, %2\n\t"
+		     "je 2f\n\t"
+		     "rep ; nop\n\t"
+		     "movzwl %1, %2\n\t"
+		     /* don't need lfence here, because loads are in-order */
+		     "jmp 1b\n"
+		     "2:"
+		     : "+r" (inc), "+m" (lock->slock), "=&r" (tmp)
+		     :
+		     : "memory", "cc");
+}
+
+static __always_inline int __ticket_spin_trylock(raw_spinlock_t *lock)
+{
+	int tmp;
+	int 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;
+}
+
+static __always_inline void __ticket_spin_unlock(raw_spinlock_t *lock)
+{
+	asm volatile(UNLOCK_LOCK_PREFIX "incw %0"
+		     : "+m" (lock->slock)
+		     :
+		     : "memory", "cc");
+}
+#endif
+
+static inline int __ticket_spin_is_locked(raw_spinlock_t *lock)
+{
+	int tmp = ACCESS_ONCE(lock->slock);
+
+	return !!(((tmp >> TICKET_SHIFT) ^ tmp) & ((1 << TICKET_SHIFT) - 1));
+}
+
+static inline int __ticket_spin_is_contended(raw_spinlock_t *lock)
+{
+	int tmp = ACCESS_ONCE(lock->slock);
+
+	return (((tmp >> TICKET_SHIFT) - tmp) & ((1 << TICKET_SHIFT) - 1)) > 1;
+}
+
+#ifdef CONFIG_PARAVIRT
+/*
+ * Define virtualization-friendly old-style lock byte lock, for use in
+ * pv_lock_ops if desired.
+ *
+ * This differs from the pre-2.6.24 spinlock by always using xchgb
+ * rather than decb to take the lock; this allows it to use a
+ * zero-initialized lock structure.  It also maintains a 1-byte
+ * contention counter, so that we can implement
+ * __byte_spin_is_contended.
+ */
+struct __byte_spinlock {
+	s8 lock;
+	s8 spinners;
+};
+
+static inline int __byte_spin_is_locked(raw_spinlock_t *lock)
+{
+	struct __byte_spinlock *bl = (struct __byte_spinlock *)lock;
+	return bl->lock != 0;
+}
+
+static inline int __byte_spin_is_contended(raw_spinlock_t *lock)
+{
+	struct __byte_spinlock *bl = (struct __byte_spinlock *)lock;
+	return bl->spinners != 0;
+}
+
+static inline void __byte_spin_lock(raw_spinlock_t *lock)
+{
+	struct __byte_spinlock *bl = (struct __byte_spinlock *)lock;
+	s8 val = 1;
+
+	asm("1: xchgb %1, %0\n"
+	    "   test %1,%1\n"
+	    "   jz 3f\n"
+	    "   " LOCK_PREFIX "incb %2\n"
+	    "2: rep;nop\n"
+	    "   cmpb $1, %0\n"
+	    "   je 2b\n"
+	    "   " LOCK_PREFIX "decb %2\n"
+	    "   jmp 1b\n"
+	    "3:"
+	    : "+m" (bl->lock), "+q" (val), "+m" (bl->spinners): : "memory");
+}
+
+static inline int __byte_spin_trylock(raw_spinlock_t *lock)
+{
+	struct __byte_spinlock *bl = (struct __byte_spinlock *)lock;
+	u8 old = 1;
+
+	asm("xchgb %1,%0"
+	    : "+m" (bl->lock), "+q" (old) : : "memory");
+
+	return old == 0;
+}
+
+static inline void __byte_spin_unlock(raw_spinlock_t *lock)
+{
+	struct __byte_spinlock *bl = (struct __byte_spinlock *)lock;
+	smp_wmb();
+	bl->lock = 0;
+}
+#else  /* !CONFIG_PARAVIRT */
+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);
+}
+
+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);
+}
+
+#endif	/* CONFIG_PARAVIRT */
+
+static inline void __raw_spin_unlock_wait(raw_spinlock_t *lock)
+{
+	while (__raw_spin_is_locked(lock))
+		cpu_relax();
+}
+
+/*
+ * 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 __raw_read_can_lock(raw_rwlock_t *lock)
+{
+	return (int)(lock)->lock > 0;
+}
+
+/**
+ * write_can_lock - would write_trylock() succeed?
+ * @lock: the rwlock in question.
+ */
+static inline int __raw_write_can_lock(raw_rwlock_t *lock)
+{
+	return (lock)->lock == RW_LOCK_BIAS;
+}
+
+static inline void __raw_read_lock(raw_rwlock_t *rw)
+{
+	asm volatile(LOCK_PREFIX " subl $1,(%0)\n\t"
+		     "jns 1f\n"
+		     "call __read_lock_failed\n\t"
+		     "1:\n"
+		     ::LOCK_PTR_REG (rw) : "memory");
+}
+
+static inline void __raw_write_lock(raw_rwlock_t *rw)
+{
+	asm volatile(LOCK_PREFIX " subl %1,(%0)\n\t"
+		     "jz 1f\n"
+		     "call __write_lock_failed\n\t"
+		     "1:\n"
+		     ::LOCK_PTR_REG (rw), "i" (RW_LOCK_BIAS) : "memory");
+}
+
+static inline int __raw_read_trylock(raw_rwlock_t *lock)
+{
+	atomic_t *count = (atomic_t *)lock;
+
+	atomic_dec(count);
+	if (atomic_read(count) >= 0)
+		return 1;
+	atomic_inc(count);
+	return 0;
+}
+
+static inline int __raw_write_trylock(raw_rwlock_t *lock)
+{
+	atomic_t *count = (atomic_t *)lock;
+
+	if (atomic_sub_and_test(RW_LOCK_BIAS, count))
+		return 1;
+	atomic_add(RW_LOCK_BIAS, count);
+	return 0;
+}
+
+static inline void __raw_read_unlock(raw_rwlock_t *rw)
+{
+	asm volatile(LOCK_PREFIX "incl %0" :"+m" (rw->lock) : : "memory");
+}
+
+static inline void __raw_write_unlock(raw_rwlock_t *rw)
+{
+	asm volatile(LOCK_PREFIX "addl %1, %0"
+		     : "+m" (rw->lock) : "i" (RW_LOCK_BIAS) : "memory");
+}
+
+#define _raw_spin_relax(lock)	cpu_relax()
+#define _raw_read_relax(lock)	cpu_relax()
+#define _raw_write_relax(lock)	cpu_relax()
+
+#endif /* ASM_X86__SPINLOCK_H */