135 lines
3.2 KiB
C
135 lines
3.2 KiB
C
/*
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* Copyright (c) 2020 Institute of Parallel And Distributed Systems (IPADS),
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* Shanghai Jiao Tong University (SJTU) OS-Lab-2020 (i.e., ChCore) is licensed
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* under the Mulan PSL v1. You can use this software according to the terms and
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* conditions of the Mulan PSL v1. You may obtain a copy of Mulan PSL v1 at:
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* http://license.coscl.org.cn/MulanPSL
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* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY
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* KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
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* NON-INFRINGEMENT, MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE. See the
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* Mulan PSL v1 for more details.
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*/
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#include <common/smp.h>
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#include <common/sync.h>
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#include <common/errno.h>
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#include <common/kprint.h>
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#include <common/lock.h>
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#include <common/macro.h>
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#include <common/types.h>
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struct lock big_kernel_lock;
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int lock_init(struct lock *lock)
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{
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BUG_ON(!lock);
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/* Initialize ticket lock */
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lock->owner = 0;
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lock->next = 0;
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return 0;
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}
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/**
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* Lock the ticket lock
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* This function will block until the lock is held
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*/
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void lock(struct lock *lock)
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{
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u32 lockval = 0, newval = 0, ret = 0;
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BUG_ON(!lock);
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/**
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* The following asm code means:
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*
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* lock->next = fetch_and_add(1);
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* while(lock->next != lock->owner);
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*/
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asm volatile (" prfm pstl1strm, %3\n"
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"1: ldaxr %w0, %3\n"
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" add %w1, %w0, #0x1\n"
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" stxr %w2, %w1, %3\n"
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" cbnz %w2, 1b\n"
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"2: ldar %w2, %4\n"
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" cmp %w0, %w2\n"
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" b.ne 2b\n":"=&r" (lockval), "=&r"(newval),
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"=&r"(ret), "+Q"(lock->next)
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:"Q"(lock->owner)
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:"memory");
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}
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/**
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* Try to lock the ticket lock
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* Return 0 if succeed, -1 otherwise
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*/
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int try_lock(struct lock *lock)
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{
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u32 lockval = 0, newval = 0, ret = 0, ownerval = 0;
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BUG_ON(!lock);
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asm volatile (" prfm pstl1strm, %4\n" " ldaxr %w0, %4\n" " ldar %w3, %5\n" " add %w1, %w0, #0x1\n" " cmp %w0, %w3\n" " b.ne 1f\n" " stxr %w2, %w1, %4\n" " cbz %w2, 2f\n" "1: mov %w2, #0xffffffffffffffff\n" /* fail */
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" b 3f\n" "2: mov %w2, #0x0\n" /* success */
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" dmb ish\n" /* barrier */
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"3:\n":"=&r" (lockval), "=&r"(newval), "=&r"(ret),
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"=&r"(ownerval), "+Q"(lock->next)
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:"Q"(lock->owner)
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:"memory");
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return ret;
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}
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/**
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* Unlock the ticket lock
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*/
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void unlock(struct lock *lock)
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{
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BUG_ON(!lock);
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asm volatile ("dmb ish");
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/**
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* Lab4
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* Unlock the ticket lock here
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* Your code should be no more than 5 lines
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*/
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// 因为仍在临界区，所以可以直接 ++
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lock->owner++;
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}
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/**
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* Lab4
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* Check whether the ticket lock is locked
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* Return 1 if locked, 0 otherwise
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* Your code should be no more than 5 lines
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*/
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int is_locked(struct lock *lock)
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{
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return lock->owner != lock->next;
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}
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/**
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* Lab4
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* Initialization of the big kernel lock
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*/
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void kernel_lock_init(void)
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{
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lock_init(&big_kernel_lock);
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}
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/**
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* Lab4
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* Acquire the big kernel lock
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*/
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void lock_kernel(void)
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{
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lock(&big_kernel_lock);
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}
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/**
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* Lab4
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* Release the big kernel lock
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*/
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void unlock_kernel(void)
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{
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unlock(&big_kernel_lock);
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}
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