mutex.h

File system using stacked.

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996-2002
 *	Sleepycat Software.  All rights reserved.
 *
 * $Id: mutex.h,v 1.1.1.1 2004/08/19 23:53:56 gopalan Exp $
 */

#ifndef _DB_MUTEX_H_
#define	_DB_MUTEX_H_



/*
 * Some of the Berkeley DB ports require single-threading at various
 * places in the code.  In those cases, these #defines will be set.
 */
#define	DB_BEGIN_SINGLE_THREAD
#define	DB_END_SINGLE_THREAD

/*********************************************************************
 * kernel semaphore interface to use with kdb3.
 *********************************************************************/
#ifdef __KERNEL__
#define	MUTEX_FIELDS	
#include <asm/semaphore.h>
	struct semaphore tas;		/* Mutex. */			
#define	MUTEX_ALIGN	 sizeof(struct semaphore)
/*XXX*/

#ifdef LOAD_ACTUAL_MUTEX_CODE
#define	MUTEX_DESTROY(x)                /*XXX: sema_destroy(x).
					 *Commented for porting to
					 *kdb3.
					 */
#define	MUTEX_INIT(x)	 sema_init(x, 1)
#define	MUTEX_SET(x)	 (down_interruptible(x) == 0)
#define	MUTEX_UNSET(x)	 up(x)
#endif
#endif /* __KERNEL__ */





#ifndef __KERNEL__ 

/*********************************************************************
 * POSIX.1 pthreads interface.
 *********************************************************************/
//#ifdef HAVE_MUTEX_PTHREADS
//#include <pthread.h>

//#define	MUTEX_FIELDS							
					 //	pthread_mutex_t mutex;		/* Mutex. */		     
					 //	pthread_cond_t  cond;		/* Condition variable. */
//#endif

/*********************************************************************
 * Solaris lwp threads interface.
 *
 * !!!
 * We use LWP mutexes on Solaris instead of UI or POSIX mutexes (both of
 * which are available), for two reasons.  First, the Solaris C library
 * includes versions of the both UI and POSIX thread mutex interfaces, but
 * they are broken in that they don't support inter-process locking, and
 * there's no way to detect it, e.g., calls to configure the mutexes for
 * inter-process locking succeed without error.  So, we use LWP mutexes so
 * that we don't fail in fairly undetectable ways because the application
 * wasn't linked with the appropriate threads library.  Second, there were
 * bugs in SunOS 5.7 (Solaris 7) where if an application loaded the C library
 * before loading the libthread/libpthread threads libraries (e.g., by using
 * dlopen to load the DB library), the pwrite64 interface would be translated
 * into a call to pwrite and DB would drop core.
 *********************************************************************/
#ifdef HAVE_MUTEX_SOLARIS_LWP
/*
 * XXX
 * Don't change <synch.h> to <sys/lwp.h> -- although lwp.h is listed in the
 * Solaris manual page as the correct include to use, it causes the Solaris
 * compiler on SunOS 2.6 to fail.
 */
#include <synch.h>

#define	MUTEX_FIELDS							\
	lwp_mutex_t mutex;		/* Mutex. */			\
	lwp_cond_t cond;		/* Condition variable. */
#endif

/*********************************************************************
 * Solaris/Unixware threads interface.
 *********************************************************************/
#ifdef HAVE_MUTEX_UI_THREADS
#include <thread.h>
#include <synch.h>

#define	MUTEX_FIELDS							\
	mutex_t mutex;			/* Mutex. */			\
	cond_t  cond;			/* Condition variable. */
#endif

/*********************************************************************
 * AIX C library functions.
 *********************************************************************/
#ifdef HAVE_MUTEX_AIX_CHECK_LOCK
#include <sys/atomic_op.h>
typedef int tsl_t;
#define	MUTEX_ALIGN	sizeof(int)

#ifdef LOAD_ACTUAL_MUTEX_CODE
#define	MUTEX_INIT(x)	0
#define	MUTEX_SET(x)	(!_check_lock(x, 0, 1))
#define	MUTEX_UNSET(x)	_clear_lock(x, 0)
#endif
#endif

/*********************************************************************
 * General C library functions (msemaphore).
 *
 * !!!
 * Check for HPPA as a special case, because it requires unusual alignment,
 * and doesn't support semaphores in malloc(3) or shmget(2) memory.
 *
 * !!!
 * Do not remove the MSEM_IF_NOWAIT flag.  The problem is that if a single
 * process makes two msem_lock() calls in a row, the second one returns an
 * error.  We depend on the fact that we can lock against ourselves in the
 * locking subsystem, where we set up a mutex so that we can block ourselves.
 * Tested on OSF1 v4.0.
 *********************************************************************/
#ifdef HAVE_MUTEX_HPPA_MSEM_INIT
#define	MUTEX_NO_MALLOC_LOCKS
#define	MUTEX_NO_SHMGET_LOCKS

#define	MUTEX_ALIGN	16
#endif

#if defined(HAVE_MUTEX_MSEM_INIT) || defined(HAVE_MUTEX_HPPA_MSEM_INIT)
#include <sys/mman.h>
typedef msemaphore tsl_t;

#ifndef MUTEX_ALIGN
#define	MUTEX_ALIGN	sizeof(int)
#endif

#ifdef LOAD_ACTUAL_MUTEX_CODE
#define	MUTEX_INIT(x)	(msem_init(x, MSEM_UNLOCKED) <= (msemaphore *)0)
#define	MUTEX_SET(x)	(!msem_lock(x, MSEM_IF_NOWAIT))
#define	MUTEX_UNSET(x)	msem_unlock(x, 0)
#endif
#endif

/*********************************************************************
 * Plan 9 library functions.
 *********************************************************************/
#ifdef HAVE_MUTEX_PLAN9
typedef Lock tsl_t;

#define	MUTEX_ALIGN	sizeof(int)

#define	MUTEX_INIT(x)	(memset(x, 0, sizeof(Lock)), 0)
#define	MUTEX_SET(x)	canlock(x)
#define	MUTEX_UNSET(x)	unlock(x)
#endif

/*********************************************************************
 * Reliant UNIX C library functions.
 *********************************************************************/
#ifdef HAVE_MUTEX_RELIANTUNIX_INITSPIN
#include <ulocks.h>
typedef spinlock_t tsl_t;

#ifdef LOAD_ACTUAL_MUTEX_CODE
#define	MUTEX_INIT(x)	(initspin(x, 1), 0)
#define	MUTEX_SET(x)	(cspinlock(x) == 0)
#define	MUTEX_UNSET(x)	spinunlock(x)
#endif
#endif

/*********************************************************************
 * General C library functions (POSIX 1003.1 sema_XXX).
 *
 * !!!
 * Never selected by autoconfig in this release (semaphore calls are known
 * to not work in Solaris 5.5).
 *********************************************************************/
#ifdef HAVE_MUTEX_SEMA_INIT
#include <synch.h>
typedef sema_t tsl_t;
#define	MUTEX_ALIGN	 sizeof(int)

#ifdef LOAD_ACTUAL_MUTEX_CODE
#define	MUTEX_DESTROY(x) sema_destroy(x)
#define	MUTEX_INIT(x)	 (sema_init(x, 1, USYNC_PROCESS, NULL) != 0)
#define	MUTEX_SET(x)	 (sema_wait(x) == 0)
#define	MUTEX_UNSET(x)	 sema_post(x)
#endif
#endif

/*********************************************************************
 * SGI C library functions.
 *********************************************************************/
#ifdef HAVE_MUTEX_SGI_INIT_LOCK
#include <abi_mutex.h>
typedef abilock_t tsl_t;
#define	MUTEX_ALIGN	sizeof(int)

#ifdef LOAD_ACTUAL_MUTEX_CODE
#define	MUTEX_INIT(x)	(init_lock(x) != 0)
#define	MUTEX_SET(x)	(!acquire_lock(x))
#define	MUTEX_UNSET(x)	release_lock(x)
#endif
#endif

/*********************************************************************
 * Solaris C library functions.
 *
 * !!!
 * These are undocumented functions, but they're the only ones that work
 * correctly as far as we know.
 *********************************************************************/
#ifdef HAVE_MUTEX_SOLARIS_LOCK_TRY
#include <sys/machlock.h>
typedef lock_t tsl_t;
#define	MUTEX_ALIGN	sizeof(int)

#ifdef LOAD_ACTUAL_MUTEX_CODE
#define	MUTEX_INIT(x)	0
#define	MUTEX_SET(x)	_lock_try(x)
#define	MUTEX_UNSET(x)	_lock_clear(x)
#endif
#endif

/*********************************************************************
 * VMS.
 *********************************************************************/
#ifdef HAVE_MUTEX_VMS
#include <sys/mman.h>;
#include <builtins.h>
typedef unsigned char tsl_t;
#define	MUTEX_ALIGN		sizeof(unsigned int)

#ifdef LOAD_ACTUAL_MUTEX_CODE
#ifdef __ALPHA
#define	MUTEX_SET(tsl)		(!__TESTBITSSI(tsl, 0))
#else /* __VAX */
#define	MUTEX_SET(tsl)		(!(int)_BBSSI(0, tsl))
#endif
#define	MUTEX_UNSET(tsl)	(*(tsl) = 0)
#define	MUTEX_INIT(tsl)		MUTEX_UNSET(tsl)
#endif
#endif

/*********************************************************************
 * VxWorks
 * Use basic binary semaphores in VxWorks, as we currently do not need
 * any special features.  We do need the ability to single-thread the
 * entire system, however, because VxWorks doesn't support the open(2)
 * flag O_EXCL, the mechanism we normally use to single thread access
 * when we're first looking for a DB environment.
 *********************************************************************/
#ifdef HAVE_MUTEX_VXWORKS
#include "taskLib.h"
typedef SEM_ID tsl_t;
#define	MUTEX_ALIGN		sizeof(unsigned int)

#ifdef LOAD_ACTUAL_MUTEX_CODE
#define	MUTEX_SET(tsl)		(semTake((*tsl), WAIT_FOREVER) == OK)
#define	MUTEX_UNSET(tsl)	(semGive((*tsl)))
#define	MUTEX_INIT(tsl)							\
	((*(tsl) = semBCreate(SEM_Q_FIFO, SEM_FULL)) == NULL)
#define	MUTEX_DESTROY(tsl)	semDelete(*tsl)
#endif

/*
 * Use the taskLock() mutex to eliminate a race where two tasks are
 * trying to initialize the global lock at the same time.
 */
#undef	DB_BEGIN_SINGLE_THREAD
#define	DB_BEGIN_SINGLE_THREAD						\
do {									\
	if (DB_GLOBAL(db_global_init))					\
		(void)semTake(DB_GLOBAL(db_global_lock), WAIT_FOREVER);	\
	else {								\
		taskLock();						\
		if (DB_GLOBAL(db_global_init)) {			\
			taskUnlock();					\
			(void)semTake(DB_GLOBAL(db_global_lock),	\
			    WAIT_FOREVER);				\
			continue;					\
		}							\
		DB_GLOBAL(db_global_lock) =				\
		    semBCreate(SEM_Q_FIFO, SEM_EMPTY);			\
		if (DB_GLOBAL(db_global_lock) != NULL)			\
			DB_GLOBAL(db_global_init) = 1;			\
		taskUnlock();						\
	}								\
} while (DB_GLOBAL(db_global_init) == 0)
#undef	DB_END_SINGLE_THREAD
#define	DB_END_SINGLE_THREAD	(void)semGive(DB_GLOBAL(db_global_lock))
#endif

/*********************************************************************
 * Win16
 *
 * Win16 spinlocks are simple because we cannot possibly be preempted.
 *
 * !!!
 * We should simplify this by always returning a no-need-to-lock lock
 * when we initialize the mutex.
 *********************************************************************/
#ifdef HAVE_MUTEX_WIN16
typedef unsigned int tsl_t;
#define	MUTEX_ALIGN		sizeof(unsigned int)

#ifdef LOAD_ACTUAL_MUTEX_CODE
#define	MUTEX_INIT(x)		0
#define	MUTEX_SET(tsl)		(*(tsl) = 1)
#define	MUTEX_UNSET(tsl)	(*(tsl) = 0)
#endif
#endif

/*********************************************************************
 * Win32
 *********************************************************************/
#ifdef HAVE_MUTEX_WIN32
#define	MUTEX_FIELDS							\
	LONG tas;							\
	LONG nwaiters;							\
	u_int32_t id;	/* ID used for creating events */		\

#if defined(LOAD_ACTUAL_MUTEX_CODE)
#define	MUTEX_SET(tsl)		(!InterlockedExchange((PLONG)tsl, 1))
#define	MUTEX_UNSET(tsl)	(*(tsl) = 0)
#define	MUTEX_INIT(tsl)		MUTEX_UNSET(tsl)
#endif
#endif

/*********************************************************************
 * 68K/gcc assembly.
 *********************************************************************/
#ifdef HAVE_MUTEX_68K_GCC_ASSEMBLY
typedef unsigned char tsl_t;

#ifdef LOAD_ACTUAL_MUTEX_CODE
/*
 * For gcc/68K, 0 is clear, 1 is set.
 */
#define	MUTEX_SET(tsl) ({						\
	register tsl_t *__l = (tsl);					\
	int __r;							\
	    asm volatile("tas  %1; \n					\
			  seq  %0"					\
		: "=dm" (__r), "=m" (*__l)				\
		: "1" (*__l)						\
		);							\
	__r & 1;							\
})

#define	MUTEX_UNSET(tsl)	(*(tsl) = 0)
#define	MUTEX_INIT(tsl)		MUTEX_UNSET(tsl)
#endif
#endif

/*********************************************************************
 * ALPHA/gcc assembly.
 *********************************************************************/
#ifdef HAVE_MUTEX_ALPHA_GCC_ASSEMBLY
typedef u_int32_t tsl_t;
#define	MUTEX_ALIGN	4

#ifdef LOAD_ACTUAL_MUTEX_CODE
/*
 * For gcc/alpha.  Should return 0 if could not acquire the lock, 1 if
 * lock was acquired properly.
 */
#ifdef __GNUC__
static inline int
MUTEX_SET(tsl_t *tsl) {
	register tsl_t *__l = tsl;
	register tsl_t __r;
	asm volatile(
		"1:	ldl_l	%0,%2\n"
		"	blbs	%0,2f\n"
		"	or	$31,1,%0\n"
		"	stl_c	%0,%1\n"
		"	beq	%0,3f\n"
		"	mb\n"
		"	br	3f\n"
		"2:	xor	%0,%0\n"
		"3:"
		: "=&r"(__r), "=m"(*__l) : "1"(*__l) : "memory");
	return __r;
}

/*
 * Unset mutex. Judging by Alpha Architecture Handbook, the mb instruction
 * might be necessary before unlocking
 */
static inline int
MUTEX_UNSET(tsl_t *tsl) {
	asm volatile("	mb\n");
	return *tsl = 0;
}
#endif

#ifdef __DECC
#include <alpha/builtins.h>
#define	MUTEX_SET(tsl)		(__LOCK_LONG_RETRY((tsl), 1) != 0)
#define	MUTEX_UNSET(tsl)	(*(tsl) = 0)
#endif

#define	MUTEX_INIT(tsl)		MUTEX_UNSET(tsl)
#endif
#endif

/*********************************************************************
 * ARM/gcc assembly.
 *********************************************************************/
#ifdef HAVE_MUTEX_ARM_GCC_ASSEMBLY
typedef unsigned char tsl_t;

#ifdef LOAD_ACTUAL_MUTEX_CODE
/*
 * For arm/gcc, 0 is clear, 1 is set.
 */
#define	MUTEX_SET(tsl) ({						\
	int __r;							\
	asm volatile("swpb %0, %1, [%2]"				\
	    : "=r" (__r) 						\
	    : "0" (1), "r" (tsl)					\
	    : "memory"							\
	    );								\
	__r & 1;							\
})

#define	MUTEX_UNSET(tsl)	(*(volatile tsl_t *)(tsl) = 0)
#define	MUTEX_INIT(tsl)		MUTEX_UNSET(tsl)
#endif
#endif

/*********************************************************************
 * HPPA/gcc assembly.
 *********************************************************************/
#ifdef HAVE_MUTEX_HPPA_GCC_ASSEMBLY
typedef u_int32_t tsl_t;
#define	MUTEX_ALIGN	16

#ifdef LOAD_ACTUAL_MUTEX_CODE
/*
 * The PA-RISC has a "load and clear" instead of a "test and set" instruction.
 * The 32-bit word used by that instruction must be 16-byte aligned.  We could
 * use the "aligned" attribute in GCC but that doesn't work for stack variables.
 */
#define	MUTEX_SET(tsl) ({						\
	register tsl_t *__l = (tsl);					\
	int __r;							\
	asm volatile("ldcws 0(%1),%0" : "=r" (__r) : "r" (__l));	\
	__r & 1;							\
})

#define	MUTEX_UNSET(tsl)	(*(tsl) = -1)
#define	MUTEX_INIT(tsl)		(MUTEX_UNSET(tsl), 0)
#endif
#endif

/*********************************************************************
 * IA64/gcc assembly.
 *********************************************************************/
#ifdef HAVE_MUTEX_IA64_GCC_ASSEMBLY