From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001 From: André Fabian Silva Delgado Date: Wed, 5 Aug 2015 17:04:01 -0300 Subject: Initial import --- arch/tile/lib/spinlock_64.c | 104 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 104 insertions(+) create mode 100644 arch/tile/lib/spinlock_64.c (limited to 'arch/tile/lib/spinlock_64.c') diff --git a/arch/tile/lib/spinlock_64.c b/arch/tile/lib/spinlock_64.c new file mode 100644 index 000000000..d6fb9581e --- /dev/null +++ b/arch/tile/lib/spinlock_64.c @@ -0,0 +1,104 @@ +/* + * Copyright 2011 Tilera Corporation. All Rights Reserved. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation, version 2. + * + * 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, GOOD TITLE or + * NON INFRINGEMENT. See the GNU General Public License for + * more details. + */ + +#include +#include +#include + +#include "spinlock_common.h" + +/* + * Read the spinlock value without allocating in our cache and without + * causing an invalidation to another cpu with a copy of the cacheline. + * This is important when we are spinning waiting for the lock. + */ +static inline u32 arch_spin_read_noalloc(void *lock) +{ + return atomic_cmpxchg((atomic_t *)lock, -1, -1); +} + +/* + * Wait until the high bits (current) match my ticket. + * If we notice the overflow bit set on entry, we clear it. + */ +void arch_spin_lock_slow(arch_spinlock_t *lock, u32 my_ticket) +{ + if (unlikely(my_ticket & __ARCH_SPIN_NEXT_OVERFLOW)) { + __insn_fetchand4(&lock->lock, ~__ARCH_SPIN_NEXT_OVERFLOW); + my_ticket &= ~__ARCH_SPIN_NEXT_OVERFLOW; + } + + for (;;) { + u32 val = arch_spin_read_noalloc(lock); + u32 delta = my_ticket - arch_spin_current(val); + if (delta == 0) + return; + relax((128 / CYCLES_PER_RELAX_LOOP) * delta); + } +} +EXPORT_SYMBOL(arch_spin_lock_slow); + +/* + * Check the lock to see if it is plausible, and try to get it with cmpxchg(). + */ +int arch_spin_trylock(arch_spinlock_t *lock) +{ + u32 val = arch_spin_read_noalloc(lock); + if (unlikely(arch_spin_current(val) != arch_spin_next(val))) + return 0; + return cmpxchg(&lock->lock, val, (val + 1) & ~__ARCH_SPIN_NEXT_OVERFLOW) + == val; +} +EXPORT_SYMBOL(arch_spin_trylock); + +void arch_spin_unlock_wait(arch_spinlock_t *lock) +{ + u32 iterations = 0; + while (arch_spin_is_locked(lock)) + delay_backoff(iterations++); +} +EXPORT_SYMBOL(arch_spin_unlock_wait); + +/* + * If the read lock fails due to a writer, we retry periodically + * until the value is positive and we write our incremented reader count. + */ +void __read_lock_failed(arch_rwlock_t *rw) +{ + u32 val; + int iterations = 0; + do { + delay_backoff(iterations++); + val = __insn_fetchaddgez4(&rw->lock, 1); + } while (unlikely(arch_write_val_locked(val))); +} +EXPORT_SYMBOL(__read_lock_failed); + +/* + * If we failed because there were readers, clear the "writer" bit + * so we don't block additional readers. Otherwise, there was another + * writer anyway, so our "fetchor" made no difference. Then wait, + * issuing periodic fetchor instructions, till we get the lock. + */ +void __write_lock_failed(arch_rwlock_t *rw, u32 val) +{ + int iterations = 0; + do { + if (!arch_write_val_locked(val)) + val = __insn_fetchand4(&rw->lock, ~__WRITE_LOCK_BIT); + delay_backoff(iterations++); + val = __insn_fetchor4(&rw->lock, __WRITE_LOCK_BIT); + } while (val != 0); +} +EXPORT_SYMBOL(__write_lock_failed); -- cgit v1.2.3-54-g00ecf