5db078a9be
if we hold a spin mutex, since we can trivially get into deadlocks if we start switching out of processes that hold spinlocks. Checking to see if interrupts were disabled was a sort of cheap way of doing this since most of the time interrupts were only disabled when holding a spin lock. At least on the i386. To fix this properly, use a per-process counter p_spinlocks that counts the number of spin locks currently held, and instead of checking to see if interrupts are disabled in the witness code, check to see if we hold any spin locks. Since child processes always start up with the sched lock magically held in fork_exit(), we initialize p_spinlocks to 1 for child processes. Note that proc0 doesn't go through fork_exit(), so it starts with no spin locks held. Consulting from: cp
96 lines
3.1 KiB
C
96 lines
3.1 KiB
C
/*-
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* Copyright (c) 1997 Berkeley Software Design, Inc. 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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* 3. Berkeley Software Design Inc's name may not be used to endorse or
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* 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 BERKELEY SOFTWARE DESIGN INC ``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 BERKELEY SOFTWARE DESIGN INC 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 BSDI $Id: mutex.h,v 2.7.2.35 2000/04/27 03:10:26 cp Exp $
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* $FreeBSD$
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*/
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#ifndef _MACHINE_MUTEX_H_
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#define _MACHINE_MUTEX_H_
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#ifndef LOCORE
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#ifdef _KERNEL
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#define mtx_intr_enable(mutex) (mutex)->mtx_saveintr = ALPHA_PSL_IPL_0
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/*
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* Assembly macros (for internal use only)
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*--------------------------------------------------------------------------
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*/
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/*
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* Get a spin lock, handle recusion inline.
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*/
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#define _get_spin_lock(mp, tid, opts) do { \
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u_int _ipl = alpha_pal_swpipl(ALPHA_PSL_IPL_HIGH); \
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if (!_obtain_lock((mp), (tid))) { \
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if ((mp)->mtx_lock == (uintptr_t)(tid)) \
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(mp)->mtx_recurse++; \
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else \
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_mtx_lock_spin((mp), (opts), _ipl, __FILE__, \
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__LINE__); \
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} else { \
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alpha_mb(); \
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(mp)->mtx_saveintr = _ipl; \
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} \
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} while (0)
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#endif /* _KERNEL */
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#else /* !LOCORE */
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/*
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* Simple assembly macros to get and release non-recursive spin locks
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*
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* XXX: These are presently unused and cannot be used right now. Need to be
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* re-written (they are wrong). If you plan to use this and still see
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* this message, know not to unless you fix them first! :-)
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*/
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#define MTX_ENTER(lck) \
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ldiq a0, ALPHA_PSL_IPL_HIGH; \
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call_pal PAL_OSF1_swpipl; \
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1: ldq_l a0, lck+MTX_LOCK; \
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cmpeq a0, MTX_UNOWNED, a1; \
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beq a1, 1b; \
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ldq a0, PC_CURPROC(globalp); \
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stq_c a0, lck+MTX_LOCK; \
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beq a0, 1b; \
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mb; \
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stl v0, lck+MTX_SAVEINTR
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#define MTX_EXIT(lck) \
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mb; \
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ldiq a0, MTX_UNOWNED; \
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stq a0, lck+MTX_LOCK; \
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ldl a0, lck+MTX_SAVEINTR; \
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call_pal PAL_OSF1_swpipl
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#endif /* !LOCORE */
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#endif /* __MACHINE_MUTEX_H */
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