sched: implement spinlocks
This commit is contained in:
Felix Kopp
parent
0026db4583
commit
e45f75f6bc
6 changed files with 325 additions and 3 deletions
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@ -5,6 +5,7 @@
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#include <ardix/sched.h>
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#include <arch/at91sam3x8e/interrupt.h>
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#include <arch/at91sam3x8e/spinlock.h>
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#include <stdbool.h>
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#include <toolchain.h>
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@ -12,13 +13,13 @@
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/** Enter atomic context, i.e. disable preemption */
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__always_inline void sched_atomic_enter(void)
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{
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_is_atomic_context = true;
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arch_spin_lock(&_in_atomic_context);
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}
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/** Leave atomic context, i.e. re-enable preemption */
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__always_inline void sched_atomic_leave(void)
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{
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_is_atomic_context = false;
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arch_spin_unlock(&_in_atomic_context);
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}
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/*
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110
include/arch/at91sam3x8e/spinlock.h
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110
include/arch/at91sam3x8e/spinlock.h
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@ -0,0 +1,110 @@
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/* SPDX-License-Identifier: BSD-3-Clause */
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/* See the end of this file for copyright, licensing, and warranty information. */
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#pragma once
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#include <stdint.h>
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#include <toolchain.h>
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typedef struct spinlock {
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int lock;
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} spinlock_t;
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/* This code is basically stolen from arch/arm/include/asm/spinlock.h in Linux 5.9 */
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/**
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* Initialize a spinlock.
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*
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* @param lock: Pointer to the spinlock.
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*/
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inline void arch_spinlock_init(spinlock_t *lock)
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{
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lock->lock = 0;
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}
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/**
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* Increment the lock count on a spinlock.
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*
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* @param lock: Pointer to the spinlock.
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* @returns The new lock count.
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*/
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inline int arch_spin_lock(spinlock_t *lock)
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{
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int tmp;
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int newval;
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spinlock_t lockval;
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__asm__ volatile(
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"1: ldrex %0, [%3] \n" /* lockval = *lock */
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" add %1, %0, #1 \n" /* newval = lockval.lock + 1 */
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" strex %2, %1, [%3] \n" /* *lock = newval */
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" teq %2, #0 \n" /* store successful? */
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" bne 1b \n" /* -> goto 1 if not */
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" dmb " /* memory barrier */
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: "=&r" (lockval), "=&r" (newval), "=&r" (tmp)
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: "r" (lock)
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: "cc");
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return newval;
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}
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/**
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* Decrement the lock count on a spinlock.
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*
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* @param lock: Pointer to the spinlock.
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* @returns The new lock count.
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*/
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inline int arch_spin_unlock(spinlock_t *lock)
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{
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int tmp;
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int newval;
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spinlock_t lockval;
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__asm__ volatile(
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"1: ldrex %0, [%3] \n"
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" sub %1, %0, #1 \n"
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" strex %2, %1, [%3] \n"
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" teq %2, #0 \n"
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" bne 1b \n"
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" dmb "
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: "=&r" (lockval), "=&r" (newval), "=&r" (tmp)
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: "r" (lock)
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: "cc");
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return newval;
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}
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/**
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* Get the lock count on a spinlock.
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*
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* @param lock: Pointer to the spinlock.
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*/
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__always_inline int arch_spinlock_count(spinlock_t *lock)
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{
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return lock->lock;
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}
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/*
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* Copyright (c) 2020 Felix Kopp <sandtler@sandtler.club>
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*
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* Redistribution and use in source and binary forms, with or without modification, are permitted
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* provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this list of
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* conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright notice, this list of
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* conditions and the following disclaimer in the documentation and/or other materials
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* provided with the distribution.
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* 3. Neither the name of the copyright holder nor the names of its contributors may be
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* used to endorse or promote products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT 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 THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
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* WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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33
include/arch/spinlock.h
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33
include/arch/spinlock.h
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@ -0,0 +1,33 @@
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/* SPDX-License-Identifier: BSD-3-Clause */
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/* See the end of this file for copyright, licensing, and warranty information. */
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#pragma once
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#include <arch/arch_include.h>
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#include ARCH_INCLUDE(spinlock.h)
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/*
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* Copyright (c) 2020 Felix Kopp <sandtler@sandtler.club>
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*
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* Redistribution and use in source and binary forms, with or without modification, are permitted
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* provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this list of
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* conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright notice, this list of
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* conditions and the following disclaimer in the documentation and/or other materials
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* provided with the distribution.
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* 3. Neither the name of the copyright holder nor the names of its contributors may be
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* used to endorse or promote products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT 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 THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
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* WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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96
include/ardix/atom.h
Normal file
96
include/ardix/atom.h
Normal file
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@ -0,0 +1,96 @@
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/* SPDX-License-Identifier: BSD-3-Clause */
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/* See the end of this file for copyright, licensing, and warranty information. */
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/*
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* An over-simplified approach of implementing locks on a system that
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* doesn't even support SMP. Describing the realization as "unfortunate"
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* is pretty much an understatement, it is straight up horrible because it
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* can lead to two threads failing to acquire a lock at the same time
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* (but it is platform-agnostic thanks to C11, yay!).
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*/
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#pragma once
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#include <errno.h>
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#include <stdatomic.h>
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#include <toolchain.h>
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struct atom {
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atomic_int lock;
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};
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/** Initialize an atom to be used as a lock. */
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__always_inline void atom_init(struct atom *atom)
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{
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atom->lock = 0;
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}
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/**
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* Destroy this atom or fail if it is currently locked.
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* If successful, this will make any subsequent locking attempts fail.
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*
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* @param atom: The atom to be destroyed.
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* @returns 0 on success, and `-EAGAIN` if the atom is currently locked.
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*/
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__always_inline int atom_destroy(struct atom *atom)
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{
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if (atom->lock != 0)
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return -EAGAIN;
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atom->lock = -1;
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return 0;
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}
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/**
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* Attempt to aquire a lock on an atom.
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*
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* @param atom: The atom to get the the lock on.
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* @returns 0 on success, and `-EAGAIN` if the atom was already locked by
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* another process.
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*/
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__always_inline int atom_lock(struct atom *atom)
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{
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atom->lock++;
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if (atom->lock != 1) {
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atom->lock--;
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return -EAGAIN;
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} else {
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return 0;
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}
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}
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/**
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* Release the lock on an atom.
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* Even though it is possible with the current implementation, releasing a
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* lock that isn't yours is a bad idea for obvious reasons.
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*
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* @param atom: The atom the release the lock from.
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*/
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__always_inline void atom_unlock(struct atom *atom)
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{
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atom->lock--;
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}
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/*
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* Copyright (c) 2020 Felix Kopp <sandtler@sandtler.club>
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*
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* Redistribution and use in source and binary forms, with or without modification, are permitted
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* provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this list of
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* conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright notice, this list of
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* conditions and the following disclaimer in the documentation and/or other materials
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* provided with the distribution.
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* 3. Neither the name of the copyright holder nor the names of its contributors may be
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* used to endorse or promote products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT 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 THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
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* WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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@ -60,7 +60,7 @@ struct process {
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/** The currently executing process. */
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extern struct process *_current_process;
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extern bool _is_atomic_context;
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extern spinlock_t _in_atomic_context;
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/**
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* Initialize the scheduler subsystem.
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82
include/ardix/spinlock.h
Normal file
82
include/ardix/spinlock.h
Normal file
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@ -0,0 +1,82 @@
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/* SPDX-License-Identifier: BSD-3-Clause */
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/* See the end of this file for copyright, licensing, and warranty information. */
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#pragma once
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#include <arch/spinlock.h>
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/*
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* Spinlocks in Ardix work pretty much the same as they do on Linux
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* (this is basically just a ripoff). See The Linux Kernel documentation
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* for details.
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*/
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/**
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* Initialize a spinlock.
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*
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* @param lock: Pointer to the spinlock.
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*/
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__always_inline void spinlock_init(spinlock_t *lock)
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{
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arch_spinlock_init(lock);
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}
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/**
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* Increment the lock count on a spinlock.
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* If required, block until we have exclusive access to the memory.
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*
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* @param lock: Pointer to the spinlock.
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* @returns The new lock count.
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*/
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__always_inline int spin_lock(spinlock_t *lock)
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{
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return arch_spin_lock(lock);
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}
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/**
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* Decrement the lock count on a spinlock.
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* If required, block until we have exclusive access to the memory.
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*
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* @param lock: Pointer to the spinlock.
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* @returns The new lock count.
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*/
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__always_inline int spin_unlock(spinlock_t *lock)
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{
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return arch_spin_unlock(lock);
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}
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/**
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* Get the lock count of a spinlock.
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*
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* @param lock: Pointer to the spinlock.
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* @returns The current lock count.
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*/
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__always_inline int spinlock_count(spinlock_t *lock)
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{
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return arch_spinlock_count(lock);
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}
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/*
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* Copyright (c) 2020 Felix Kopp <sandtler@sandtler.club>
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*
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* Redistribution and use in source and binary forms, with or without modification, are permitted
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* provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this list of
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* conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright notice, this list of
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* conditions and the following disclaimer in the documentation and/or other materials
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* provided with the distribution.
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||||
* 3. Neither the name of the copyright holder nor the names of its contributors may be
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* used to endorse or promote products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT 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 THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
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* WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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