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e5931943d0
Name space cleanup for rwlock functions. No functional change. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: linux-arch@vger.kernel.org
310 lines
7.6 KiB
C
310 lines
7.6 KiB
C
#ifndef _ASM_X86_SPINLOCK_H
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#define _ASM_X86_SPINLOCK_H
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#include <asm/atomic.h>
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#include <asm/rwlock.h>
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#include <asm/page.h>
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#include <asm/processor.h>
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#include <linux/compiler.h>
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#include <asm/paravirt.h>
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/*
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* Your basic SMP spinlocks, allowing only a single CPU anywhere
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*
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* Simple spin lock operations. There are two variants, one clears IRQ's
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* on the local processor, one does not.
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*
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* These are fair FIFO ticket locks, which are currently limited to 256
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* CPUs.
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*
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* (the type definitions are in asm/spinlock_types.h)
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*/
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#ifdef CONFIG_X86_32
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# define LOCK_PTR_REG "a"
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# define REG_PTR_MODE "k"
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#else
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# define LOCK_PTR_REG "D"
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# define REG_PTR_MODE "q"
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#endif
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#if defined(CONFIG_X86_32) && \
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(defined(CONFIG_X86_OOSTORE) || defined(CONFIG_X86_PPRO_FENCE))
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/*
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* On PPro SMP or if we are using OOSTORE, we use a locked operation to unlock
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* (PPro errata 66, 92)
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*/
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# define UNLOCK_LOCK_PREFIX LOCK_PREFIX
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#else
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# define UNLOCK_LOCK_PREFIX
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#endif
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/*
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* Ticket locks are conceptually two parts, one indicating the current head of
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* the queue, and the other indicating the current tail. The lock is acquired
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* by atomically noting the tail and incrementing it by one (thus adding
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* ourself to the queue and noting our position), then waiting until the head
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* becomes equal to the the initial value of the tail.
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*
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* We use an xadd covering *both* parts of the lock, to increment the tail and
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* also load the position of the head, which takes care of memory ordering
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* issues and should be optimal for the uncontended case. Note the tail must be
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* in the high part, because a wide xadd increment of the low part would carry
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* up and contaminate the high part.
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*
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* With fewer than 2^8 possible CPUs, we can use x86's partial registers to
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* save some instructions and make the code more elegant. There really isn't
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* much between them in performance though, especially as locks are out of line.
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*/
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#if (NR_CPUS < 256)
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#define TICKET_SHIFT 8
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static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
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{
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short inc = 0x0100;
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asm volatile (
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LOCK_PREFIX "xaddw %w0, %1\n"
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"1:\t"
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"cmpb %h0, %b0\n\t"
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"je 2f\n\t"
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"rep ; nop\n\t"
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"movb %1, %b0\n\t"
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/* don't need lfence here, because loads are in-order */
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"jmp 1b\n"
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"2:"
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: "+Q" (inc), "+m" (lock->slock)
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:
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: "memory", "cc");
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}
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static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
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{
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int tmp, new;
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asm volatile("movzwl %2, %0\n\t"
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"cmpb %h0,%b0\n\t"
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"leal 0x100(%" REG_PTR_MODE "0), %1\n\t"
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"jne 1f\n\t"
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LOCK_PREFIX "cmpxchgw %w1,%2\n\t"
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"1:"
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"sete %b1\n\t"
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"movzbl %b1,%0\n\t"
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: "=&a" (tmp), "=&q" (new), "+m" (lock->slock)
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:
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: "memory", "cc");
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return tmp;
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}
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static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
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{
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asm volatile(UNLOCK_LOCK_PREFIX "incb %0"
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: "+m" (lock->slock)
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:
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: "memory", "cc");
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}
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#else
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#define TICKET_SHIFT 16
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static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
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{
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int inc = 0x00010000;
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int tmp;
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asm volatile(LOCK_PREFIX "xaddl %0, %1\n"
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"movzwl %w0, %2\n\t"
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"shrl $16, %0\n\t"
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"1:\t"
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"cmpl %0, %2\n\t"
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"je 2f\n\t"
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"rep ; nop\n\t"
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"movzwl %1, %2\n\t"
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/* don't need lfence here, because loads are in-order */
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"jmp 1b\n"
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"2:"
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: "+r" (inc), "+m" (lock->slock), "=&r" (tmp)
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:
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: "memory", "cc");
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}
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static __always_inline int __ticket_spin_trylock(arch_spinlock_t *lock)
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{
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int tmp;
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int new;
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asm volatile("movl %2,%0\n\t"
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"movl %0,%1\n\t"
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"roll $16, %0\n\t"
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"cmpl %0,%1\n\t"
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"leal 0x00010000(%" REG_PTR_MODE "0), %1\n\t"
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"jne 1f\n\t"
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LOCK_PREFIX "cmpxchgl %1,%2\n\t"
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"1:"
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"sete %b1\n\t"
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"movzbl %b1,%0\n\t"
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: "=&a" (tmp), "=&q" (new), "+m" (lock->slock)
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:
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: "memory", "cc");
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return tmp;
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}
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static __always_inline void __ticket_spin_unlock(arch_spinlock_t *lock)
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{
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asm volatile(UNLOCK_LOCK_PREFIX "incw %0"
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: "+m" (lock->slock)
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:
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: "memory", "cc");
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}
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#endif
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static inline int __ticket_spin_is_locked(arch_spinlock_t *lock)
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{
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int tmp = ACCESS_ONCE(lock->slock);
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return !!(((tmp >> TICKET_SHIFT) ^ tmp) & ((1 << TICKET_SHIFT) - 1));
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}
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static inline int __ticket_spin_is_contended(arch_spinlock_t *lock)
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{
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int tmp = ACCESS_ONCE(lock->slock);
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return (((tmp >> TICKET_SHIFT) - tmp) & ((1 << TICKET_SHIFT) - 1)) > 1;
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}
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#ifndef CONFIG_PARAVIRT_SPINLOCKS
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static inline int arch_spin_is_locked(arch_spinlock_t *lock)
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{
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return __ticket_spin_is_locked(lock);
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}
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static inline int arch_spin_is_contended(arch_spinlock_t *lock)
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{
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return __ticket_spin_is_contended(lock);
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}
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#define arch_spin_is_contended arch_spin_is_contended
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static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
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{
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__ticket_spin_lock(lock);
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}
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static __always_inline int arch_spin_trylock(arch_spinlock_t *lock)
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{
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return __ticket_spin_trylock(lock);
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}
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static __always_inline void arch_spin_unlock(arch_spinlock_t *lock)
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{
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__ticket_spin_unlock(lock);
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}
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static __always_inline void arch_spin_lock_flags(arch_spinlock_t *lock,
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unsigned long flags)
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{
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arch_spin_lock(lock);
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}
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#endif /* CONFIG_PARAVIRT_SPINLOCKS */
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static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
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{
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while (arch_spin_is_locked(lock))
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cpu_relax();
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}
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/*
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* Read-write spinlocks, allowing multiple readers
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* but only one writer.
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*
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* NOTE! it is quite common to have readers in interrupts
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* but no interrupt writers. For those circumstances we
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* can "mix" irq-safe locks - any writer needs to get a
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* irq-safe write-lock, but readers can get non-irqsafe
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* read-locks.
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*
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* On x86, we implement read-write locks as a 32-bit counter
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* with the high bit (sign) being the "contended" bit.
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*/
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/**
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* read_can_lock - would read_trylock() succeed?
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* @lock: the rwlock in question.
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*/
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static inline int arch_read_can_lock(arch_rwlock_t *lock)
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{
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return (int)(lock)->lock > 0;
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}
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/**
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* write_can_lock - would write_trylock() succeed?
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* @lock: the rwlock in question.
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*/
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static inline int arch_write_can_lock(arch_rwlock_t *lock)
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{
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return (lock)->lock == RW_LOCK_BIAS;
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}
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static inline void arch_read_lock(arch_rwlock_t *rw)
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{
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asm volatile(LOCK_PREFIX " subl $1,(%0)\n\t"
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"jns 1f\n"
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"call __read_lock_failed\n\t"
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"1:\n"
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::LOCK_PTR_REG (rw) : "memory");
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}
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static inline void arch_write_lock(arch_rwlock_t *rw)
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{
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asm volatile(LOCK_PREFIX " subl %1,(%0)\n\t"
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"jz 1f\n"
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"call __write_lock_failed\n\t"
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"1:\n"
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::LOCK_PTR_REG (rw), "i" (RW_LOCK_BIAS) : "memory");
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}
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static inline int arch_read_trylock(arch_rwlock_t *lock)
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{
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atomic_t *count = (atomic_t *)lock;
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if (atomic_dec_return(count) >= 0)
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return 1;
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atomic_inc(count);
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return 0;
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}
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static inline int arch_write_trylock(arch_rwlock_t *lock)
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{
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atomic_t *count = (atomic_t *)lock;
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if (atomic_sub_and_test(RW_LOCK_BIAS, count))
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return 1;
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atomic_add(RW_LOCK_BIAS, count);
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return 0;
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}
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static inline void arch_read_unlock(arch_rwlock_t *rw)
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{
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asm volatile(LOCK_PREFIX "incl %0" :"+m" (rw->lock) : : "memory");
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}
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static inline void arch_write_unlock(arch_rwlock_t *rw)
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{
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asm volatile(LOCK_PREFIX "addl %1, %0"
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: "+m" (rw->lock) : "i" (RW_LOCK_BIAS) : "memory");
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}
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#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
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#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
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#define arch_spin_relax(lock) cpu_relax()
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#define arch_read_relax(lock) cpu_relax()
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#define arch_write_relax(lock) cpu_relax()
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/* The {read|write|spin}_lock() on x86 are full memory barriers. */
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static inline void smp_mb__after_lock(void) { }
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#define ARCH_HAS_SMP_MB_AFTER_LOCK
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#endif /* _ASM_X86_SPINLOCK_H */
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