60 lines
2.2 KiB
C
60 lines
2.2 KiB
C
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/*
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* Copyright (C) 2018 Intel Corporation. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* * Neither the name of Intel Corporation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <hv_lib.h>
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inline int spinlock_init(spinlock_t *lock)
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{
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memset(lock, 0, sizeof(spinlock_t));
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return 0;
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}
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int spinlock_obtain(spinlock_t *lock)
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{
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/* The lock function atomically increments and exchanges the head
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* counter of the queue. If the old head of the queue is equal to the
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* tail, we have locked the spinlock. Otherwise we have to wait.
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*/
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asm volatile (" lock xaddl %%eax,%[head]\n"
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" cmpl %%eax,%[tail]\n"
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" jz 1f\n"
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"2: pause\n"
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" cmpl %%eax,%[tail]\n"
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" jnz 2b\n"
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"1:\n"
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:
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: "a" (1),
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[head] "m"(lock->head),
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[tail] "m"(lock->tail)
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: "cc", "memory");
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return 0;
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}
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