94 lines
3.5 KiB
C
94 lines
3.5 KiB
C
/*
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* Copyright (c) 2009
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* The President and Fellows of Harvard College.
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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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* 1. 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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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef _CURRENT_H_
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#define _CURRENT_H_
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/*
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* Definition of curcpu and curthread.
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*
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* The machine-dependent header should define either curcpu or curthread
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* as a macro (but not both); then we use one to get the other, and include
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* the header file needed to make that reference. (These includes are why
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* this file isn't rolled into either cpu.h or thread.h.)
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*
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* This material is machine-dependent because on some platforms it is
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* better/easier to keep track of curcpu and make curthread be
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* curcpu->c_curthread, and on others to keep track of curthread and
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* make curcpu be curthread->t_cpu.
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*
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* Either way we don't want retrieving curthread or curcpu to be
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* expensive; digging around in system board registers and whatnot is
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* not a very good idea. So we want to keep either curthread or curcpu
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* on-chip somewhere in some fashion.
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*
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* There are various possible approaches; for example, one might use
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* the MMU on each CPU to map that CPU's cpu structure to a fixed
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* virtual address that's the same on all CPUs. Then curcpu can be a
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* constant. (But one has to remember to use curcpu->c_self as the
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* canonical form of the pointer anywhere that's visible to other
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* CPUs.) On some CPUs the CPU number or cpu structure base address
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* can be stored in a supervisor-mode register, where it can be set up
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* during boot and then left alone. An alternative approach is to
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* reserve a register to hold curthread, and update it during context
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* switch.
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*
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* See each platform's machine/current.h for a discussion of what it
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* does and why.
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*/
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#include <machine/current.h>
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#if defined(__NEED_CURTHREAD)
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#include <cpu.h>
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#define curthread curcpu->c_curthread
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#define CURCPU_EXISTS() (curcpu != NULL)
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#endif
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#if defined(__NEED_CURCPU)
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#include <thread.h>
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#define curcpu curthread->t_cpu
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#define CURCPU_EXISTS() (curthread != NULL)
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#endif
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/*
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* Definition of curproc.
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*
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* curproc is always the current thread's process.
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*/
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#define curproc (curthread->t_proc)
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#endif /* _CURRENT_H_ */
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