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/*
* Copyright (C) 2012 ARM Ltd.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef __ASM_SPINLOCK_H
#define __ASM_SPINLOCK_H
#include <asm/lse.h>
#include <asm/spinlock_types.h>
#include <asm/processor.h>
/*
* Spinlock implementation.
*
* The memory barriers are implicit with the load-acquire and store-release
* instructions.
*/
static inline void arch_spin_lock(arch_spinlock_t *lock)
{
unsigned int tmp;
arch_spinlock_t lockval, newval;
asm volatile(
/* Atomically increment the next ticket. */
ARM64_LSE_ATOMIC_INSN(
/* LL/SC */
" prfm pstl1strm, %3\n"
"1: ldaxr %w0, %3\n"
" add %w1, %w0, %w5\n"
" stxr %w2, %w1, %3\n"
" cbnz %w2, 1b\n",
/* LSE atomics */
" mov %w2, %w5\n"
" ldadda %w2, %w0, %3\n"
__nops(3)
)
/* Did we get the lock? */
" eor %w1, %w0, %w0, ror #16\n"
" cbz %w1, 3f\n"
/*
* No: spin on the owner. Send a local event to avoid missing an
* unlock before the exclusive load.
*/
" sevl\n"
"2: wfe\n"
" ldaxrh %w2, %4\n"
" eor %w1, %w2, %w0, lsr #16\n"
" cbnz %w1, 2b\n"
/* We got the lock. Critical section starts here. */
"3:"
: "=&r" (lockval), "=&r" (newval), "=&r" (tmp), "+Q" (*lock)
: "Q" (lock->owner), "I" (1 << TICKET_SHIFT)
: "memory");
}
static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
unsigned int tmp;
arch_spinlock_t lockval;
asm volatile(ARM64_LSE_ATOMIC_INSN(
/* LL/SC */
" prfm pstl1strm, %2\n"
"1: ldaxr %w0, %2\n"
" eor %w1, %w0, %w0, ror #16\n"
" cbnz %w1, 2f\n"
" add %w0, %w0, %3\n"
" stxr %w1, %w0, %2\n"
" cbnz %w1, 1b\n"
"2:",
/* LSE atomics */
" ldr %w0, %2\n"
" eor %w1, %w0, %w0, ror #16\n"
" cbnz %w1, 1f\n"
" add %w1, %w0, %3\n"
" casa %w0, %w1, %2\n"
" sub %w1, %w1, %3\n"
" eor %w1, %w1, %w0\n"
"1:")
: "=&r" (lockval), "=&r" (tmp), "+Q" (*lock)
: "I" (1 << TICKET_SHIFT)
: "memory");
return !tmp;
}
static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
unsigned long tmp;
asm volatile(ARM64_LSE_ATOMIC_INSN(
/* LL/SC */
" ldrh %w1, %0\n"
" add %w1, %w1, #1\n"
" stlrh %w1, %0",
/* LSE atomics */
" mov %w1, #1\n"
" staddlh %w1, %0\n"
__nops(1))
: "=Q" (lock->owner), "=&r" (tmp)
:
: "memory");
}
static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
{
return lock.owner == lock.next;
}
static inline int arch_spin_is_locked(arch_spinlock_t *lock)
{
/*
* Ensure prior spin_lock operations to other locks have completed
* on this CPU before we test whether "lock" is locked.
*/
smp_mb(); /* ^^^ */
return !arch_spin_value_unlocked(READ_ONCE(*lock));
}
static inline int arch_spin_is_contended(arch_spinlock_t *lock)
{
arch_spinlock_t lockval = READ_ONCE(*lock);
return (lockval.next - lockval.owner) > 1;
}
#define arch_spin_is_contended arch_spin_is_contended
#include <asm/qrwlock.h>
/* See include/linux/spinlock.h */
#define smp_mb__after_spinlock() smp_mb()
#endif /* __ASM_SPINLOCK_H */
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