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freebsd-dev/sys/i386/include/mutex.h
John Baldwin 5db078a9be Fix mtx_legal2block. The only time that it is bad to block on a mutex is 
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
2001-03-09 07:24:17 +00:00

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/*-
* Copyright (c) 1997 Berkeley Software Design, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Berkeley Software Design Inc's name may not be used to endorse or
* promote products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* from BSDI $Id: mutex.h,v 2.7.2.35 2000/04/27 03:10:26 cp Exp $
* $FreeBSD$
*/
#ifndef _MACHINE_MUTEX_H_
#define _MACHINE_MUTEX_H_
#ifndef LOCORE
#ifdef _KERNEL
#include <machine/psl.h>
/* Global locks */
extern struct mtx clock_lock;
#define mtx_intr_enable(mutex) (mutex)->mtx_saveintr |= PSL_I
/*
* Assembly macros (for internal use only)
*------------------------------------------------------------------------------
*/
#define _V(x) __STRING(x)
#if 0
/* #ifndef I386_CPU */
/*
* For 486 and newer processors.
*/
/* Get a sleep lock, deal with recursion inline. */
#define _getlock_sleep(mtxp, tid, type) ({ \
int _res = MTX_UNOWNED; \
\
__asm __volatile ( \
" " MPLOCKED "" \
" cmpxchgl %3,%1;" /* Try */ \
" jz 1f;" /* Got it */ \
" andl $" _V(MTX_FLAGMASK) ",%0;" /* turn off spec bits */ \
" cmpl %0,%3;" /* already have it? */ \
" je 2f;" /* yes, recurse */ \
" pushl %4;" \
" pushl %5;" \
" call mtx_enter_hard;" \
" addl $8,%%esp;" \
" jmp 1f;" \
"2:" \
" " MPLOCKED "" \
" orl $" _V(MTX_RECURSE) ",%1;" \
" incl %2;" \
"1:" \
"# getlock_sleep" \
: "+a" (_res), /* 0 */ \
"+m" (mtxp->mtx_lock), /* 1 */ \
"+m" (mtxp->mtx_recurse) /* 2 */ \
: "r" (tid), /* 3 (input) */ \
"gi" (type), /* 4 */ \
"g" (mtxp) /* 5 */ \
: "cc", "memory", "ecx", "edx" /* used */ ); \
})
/* Get a spin lock, handle recursion inline (as the less common case) */
#define _getlock_spin_block(mtxp, tid, type) ({ \
int _res = MTX_UNOWNED; \
\
__asm __volatile ( \
" pushfl;" \
" cli;" \
" " MPLOCKED "" \
" cmpxchgl %3,%1;" /* Try */ \
" jz 2f;" /* got it */ \
" pushl %4;" \
" pushl %5;" \
" call mtx_enter_hard;" /* mtx_enter_hard(mtxp, type, oflags) */ \
" addl $12,%%esp;" \
" jmp 1f;" \
"2: popl %2;" /* save flags */ \
"1:" \
"# getlock_spin_block" \
: "+a" (_res), /* 0 */ \
"+m" (mtxp->mtx_lock), /* 1 */ \
"=m" (mtxp->mtx_saveintr) /* 2 */ \
: "r" (tid), /* 3 (input) */ \
"gi" (type), /* 4 */ \
"g" (mtxp) /* 5 */ \
: "cc", "memory", "ecx", "edx" /* used */ ); \
})
/*
* Get a lock without any recursion handling. Calls the hard enter function if
* we can't get it inline.
*/
#define _getlock_norecurse(mtxp, tid, type) ({ \
int _res = MTX_UNOWNED; \
\
__asm __volatile ( \
" " MPLOCKED "" \
" cmpxchgl %2,%1;" /* Try */ \
" jz 1f;" /* got it */ \
" pushl %3;" \
" pushl %4;" \
" call mtx_enter_hard;" /* mtx_enter_hard(mtxp, type) */ \
" addl $8,%%esp;" \
"1:" \
"# getlock_norecurse" \
: "+a" (_res), /* 0 */ \
"+m" (mtxp->mtx_lock) /* 1 */ \
: "r" (tid), /* 2 (input) */ \
"gi" (type), /* 3 */ \
"g" (mtxp) /* 4 */ \
: "cc", "memory", "ecx", "edx" /* used */ ); \
})
/*
* Release a sleep lock assuming we haven't recursed on it, recursion is handled
* in the hard function.
*/
#define _exitlock_norecurse(mtxp, tid, type) ({ \
int _tid = (int)(tid); \
\
__asm __volatile ( \
" " MPLOCKED "" \
" cmpxchgl %4,%0;" /* try easy rel */ \
" jz 1f;" /* released! */ \
" pushl %2;" \
" pushl %3;" \
" call mtx_exit_hard;" \
" addl $8,%%esp;" \
"1:" \
"# exitlock_norecurse" \
: "+m" (mtxp->mtx_lock), /* 0 */ \
"+a" (_tid) /* 1 */ \
: "gi" (type), /* 2 (input) */ \
"g" (mtxp), /* 3 */ \
"r" (MTX_UNOWNED) /* 4 */ \
: "cc", "memory", "ecx", "edx" /* used */ ); \
})
/*
* Release a sleep lock when its likely we recursed (the code to
* deal with simple recursion is inline).
*/
#define _exitlock(mtxp, tid, type) ({ \
int _tid = (int)(tid); \
\
__asm __volatile ( \
" " MPLOCKED "" \
" cmpxchgl %5,%0;" /* try easy rel */ \
" jz 1f;" /* released! */ \
" testl $" _V(MTX_RECURSE) ",%%eax;" /* recursed? */ \
" jnz 3f;" /* handle recursion */ \
/* Lock not recursed and contested: do the hard way */ \
" pushl %3;" \
" pushl %4;" \
" call mtx_exit_hard;" /* mtx_exit_hard(mtxp,type) */ \
" addl $8,%%esp;" \
" jmp 1f;" \
/* lock recursed, lower recursion level */ \
"3: decl %1;" /* one less level */ \
" jnz 1f;" /* still recursed, done */ \
" lock; andl $~" _V(MTX_RECURSE) ",%0;" /* turn off recurse flag */ \
"1:" \
"# exitlock" \
: "+m" (mtxp->mtx_lock), /* 0 */ \
"+m" (mtxp->mtx_recurse), /* 1 */ \
"+a" (_tid) /* 2 */ \
: "gi" (type), /* 3 (input) */ \
"g" (mtxp), /* 4 */ \
"r" (MTX_UNOWNED) /* 5 */ \
: "cc", "memory", "ecx", "edx" /* used */ ); \
})
/*
* Release a spin lock (with possible recursion).
*
* We use xchgl to clear lock (instead of simple store) to flush posting
* buffers and make the change visible to other CPU's.
*/
#define _exitlock_spin(mtxp) ({ \
int _res; \
\
__asm __volatile ( \
" movl %1,%2;" \
" decl %2;" \
" js 1f;" \
" movl %2,%1;" \
" jmp 2f;" \
"1: movl $ " _V(MTX_UNOWNED) ",%2;" \
" pushl %3;" \
" xchgl %2,%0;" \
" popfl;" \
"2:" \
"# exitlock_spin" \
: "+m" (mtxp->mtx_lock), /* 0 */ \
"+m" (mtxp->mtx_recurse), /* 1 */ \
"=r" (_res) /* 2 */ \
: "g" (mtxp->mtx_saveintr) /* 3 */ \
: "cc", "memory", "ecx" /* used */ ); \
})
#endif /* I386_CPU */
#undef _V
#endif /* _KERNEL */
#else /* !LOCORE */
/*
* Simple assembly macros to get and release mutexes.
*
* Note: All of these macros accept a "flags" argument and are analoguous
* to the mtx_lock_flags and mtx_unlock_flags general macros. If one
* desires to not pass a flag, the value 0 may be passed as second
* argument.
*
* XXX: We only have MTX_LOCK_SPIN and MTX_UNLOCK_SPIN for now, since that's
* all we use right now. We should add MTX_LOCK and MTX_UNLOCK (for sleep
* locks) in the near future, however.
*/
#define MTX_LOCK_SPIN(lck, flags) \
pushl %eax ; \
pushl %ecx ; \
pushl %ebx ; \
movl $(MTX_UNOWNED) , %eax ; \
movl PCPU(CURPROC), %ebx ; \
pushfl ; \
popl %ecx ; \
cli ; \
MPLOCKED cmpxchgl %ebx, lck+MTX_LOCK ; \
jz 2f ; \
cmpl lck+MTX_LOCK, %ebx ; \
je 3f ; \
pushl $0 ; \
pushl $0 ; \
pushl %ecx ; \
pushl $flags ; \
pushl $lck ; \
call _mtx_lock_spin ; \
addl $0x14, %esp ; \
jmp 1f ; \
3: movl lck+MTX_RECURSECNT, %ebx ; \
incl %ebx ; \
movl %ebx, lck+MTX_RECURSECNT ; \
jmp 1f ; \
2: movl %ecx, lck+MTX_SAVEINTR ; \
1: popl %ebx ; \
popl %ecx ; \
popl %eax
#define MTX_UNLOCK_SPIN(lck) \
pushl %edx ; \
pushl %eax ; \
movl lck+MTX_SAVEINTR, %edx ; \
movl lck+MTX_RECURSECNT, %eax ; \
testl %eax, %eax ; \
jne 2f ; \
movl $(MTX_UNOWNED), %eax ; \
xchgl %eax, lck+MTX_LOCK ; \
pushl %edx ; \
popfl ; \
jmp 1f ; \
2: decl %eax ; \
movl %eax, lck+MTX_RECURSECNT ; \
1: popl %eax ; \
popl %edx
/*
* XXX: These two are broken right now and need to be made to work for
* XXX: sleep locks, as the above two work for spin locks. We're not in
* XXX: too much of a rush to do these as we do not use them right now.
*/
#define MTX_ENTER(lck, type) \
pushl $0 ; /* dummy __LINE__ */ \
pushl $0 ; /* dummy __FILE__ */ \
pushl $type ; \
pushl $lck ; \
call _mtx_lock_XXX ; \
addl $16,%esp
#define MTX_EXIT(lck, type) \
pushl $0 ; /* dummy __LINE__ */ \
pushl $0 ; /* dummy __FILE__ */ \
pushl $type ; \
pushl $lck ; \
call _mtx_unlock_XXX ; \
addl $16,%esp
#endif /* !LOCORE */
#endif /* __MACHINE_MUTEX_H */
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