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c6a37e8413
critical_enter() and critical_exit() are now solely a mechanism for deferring kernel preemptions. They no longer have any affect on interrupts. This means that standalone critical sections are now very cheap as they are simply unlocked integer increments and decrements for the common case. Spin mutexes now use a separate KPI implemented in MD code: spinlock_enter() and spinlock_exit(). This KPI is responsible for providing whatever MD guarantees are needed to ensure that a thread holding a spin lock won't be preempted by any other code that will try to lock the same lock. For now all archs continue to block interrupts in a "spinlock section" as they did formerly in all critical sections. Note that I've also taken this opportunity to push a few things into MD code rather than MI. For example, critical_fork_exit() no longer exists. Instead, MD code ensures that new threads have the correct state when they are created. Also, we no longer try to fixup the idlethreads for APs in MI code. Instead, each arch sets the initial curthread and adjusts the state of the idle thread it borrows in order to perform the initial context switch. This change is largely a big NOP, but the cleaner separation it provides will allow for more efficient alternative locking schemes in other parts of the kernel (bare critical sections rather than per-CPU spin mutexes for per-CPU data for example). Reviewed by: grehan, cognet, arch@, others Tested on: i386, alpha, sparc64, powerpc, arm, possibly more
67 lines
2.3 KiB
C
67 lines
2.3 KiB
C
/*-
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* Copyright (c) 1991 Regents of the University of California.
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* 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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* 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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* 4. 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 REGENTS 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 REGENTS 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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* from: @(#)proc.h 7.1 (Berkeley) 5/15/91
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* $FreeBSD$
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*/
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#ifndef _MACHINE_PROC_H_
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#define _MACHINE_PROC_H_
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#include <machine/segments.h>
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struct proc_ldt {
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caddr_t ldt_base;
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int ldt_len;
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int ldt_refcnt;
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u_long ldt_active;
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struct segment_descriptor ldt_sd;
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};
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/*
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* Machine-dependent part of the proc structure for i386.
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*/
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struct mdthread {
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int md_spinlock_count; /* (k) */
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register_t md_saved_flags; /* (k) */
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};
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struct mdproc {
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struct proc_ldt *md_ldt; /* (j) per-process ldt */
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};
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#ifdef _KERNEL
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void set_user_ldt(struct mdproc *);
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struct proc_ldt *user_ldt_alloc(struct mdproc *, int);
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void user_ldt_free(struct thread *);
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#endif /* _KERNEL */
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#endif /* !_MACHINE_PROC_H_ */
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