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mariadb/storage/bdb/dbinc/mutex.h
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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1996-2002
* Sleepycat Software. All rights reserved.
*
* $Id: mutex.h,v 11.71 2002/09/10 01:36:48 bostic 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
/*********************************************************************
* 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; \
union { \
HANDLE event; /* Windows event HANDLE for wakeups */ \
u_int32_t id; /* ID used for shared mutexes */ \
} /* anonymous */;
#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
typedef unsigned char tsl_t;
#ifdef LOAD_ACTUAL_MUTEX_CODE
/*
* For gcc/ia64, 0 is clear, 1 is set.
*/
#define MUTEX_SET(tsl) ({ \
register tsl_t *__l = (tsl); \
long __r; \
asm volatile("xchg1 %0=%1,%3" : "=r"(__r), "=m"(*__l) : "1"(*__l), "r"(1));\
__r ^ 1; \
})
/*
* Store through a "volatile" pointer so we get a store with "release"
* semantics.
*/
#define MUTEX_UNSET(tsl) (*(volatile unsigned char *)(tsl) = 0)
#define MUTEX_INIT(tsl) MUTEX_UNSET(tsl)
#endif
#endif
/*********************************************************************
* PowerPC/gcc assembly.
*********************************************************************/
#if defined(HAVE_MUTEX_PPC_GENERIC_GCC_ASSEMBLY) || \
(HAVE_MUTEX_PPC_APPLE_GCC_ASSEMBLY)
typedef u_int32_t tsl_t;
#ifdef LOAD_ACTUAL_MUTEX_CODE
/*
* The PowerPC does a sort of pseudo-atomic locking. You set up a
* 'reservation' on a chunk of memory containing a mutex by loading the
* mutex value with LWARX. If the mutex has an 'unlocked' (arbitrary)
* value, you then try storing into it with STWCX. If no other process or
* thread broke your 'reservation' by modifying the memory containing the
* mutex, then the STCWX succeeds; otherwise it fails and you try to get
* a reservation again.
*
* While mutexes are explicitly 4 bytes, a 'reservation' applies to an
* entire cache line, normally 32 bytes, aligned naturally. If the mutex
* lives near data that gets changed a lot, there's a chance that you'll
* see more broken reservations than you might otherwise. The only
* situation in which this might be a problem is if one processor is
* beating on a variable in the same cache block as the mutex while another
* processor tries to acquire the mutex. That's bad news regardless
* because of the way it bashes caches, but if you can't guarantee that a
* mutex will reside in a relatively quiescent cache line, you might
* consider padding the mutex to force it to live in a cache line by
* itself. No, you aren't guaranteed that cache lines are 32 bytes. Some
* embedded processors use 16-byte cache lines, while some 64-bit
* processors use 128-bit cache lines. But assuming a 32-byte cache line
* won't get you into trouble for now.
*
* If mutex locking is a bottleneck, then you can speed it up by adding a
* regular LWZ load before the LWARX load, so that you can test for the
* common case of a locked mutex without wasting cycles making a reservation.
*
* 'set' mutexes have the value 1, like on Intel; the returned value from
* MUTEX_SET() is 1 if the mutex previously had its low bit clear, 0 otherwise.
*
* Mutexes on Mac OS X work the same way as the standard PowerPC version, but
* the assembler syntax is subtly different -- the standard PowerPC version
* assembles but doesn't work correctly. This version makes (unnecessary?)
* use of a stupid linker trick: __db_mutex_tas_dummy is never called, but the
* ___db_mutex_set label is used as a function name.
*/
#ifdef HAVE_MUTEX_PPC_APPLE_GCC_ASSEMBLY
extern int __db_mutex_set __P((volatile tsl_t *));
void
__db_mutex_tas_dummy()
{
__asm__ __volatile__(" \n\
.globl ___db_mutex_set \n\
___db_mutex_set: \n\
lwarx r5,0,r3 \n\
cmpwi r5,0 \n\
bne fail \n\
addi r5,r5,1 \n\
stwcx. r5,0,r3 \n\
beq success \n\
fail: \n\
li r3,0 \n\
blr \n\
success: \n\
li r3,1 \n\
blr");
}
#define MUTEX_SET(tsl) __db_mutex_set(tsl)
#endif
#ifdef HAVE_MUTEX_PPC_GENERIC_GCC_ASSEMBLY
#define MUTEX_SET(tsl) ({ \
int __one = 1; \
int __r; \
tsl_t *__l = (tsl); \
asm volatile (" \
0: \
lwarx %0,0,%1; \
cmpwi %0,0; \
bne 1f; \
stwcx. %2,0,%1; \
bne- 0b; \
1:" \
: "=&r" (__r) \
: "r" (__l), "r" (__one)); \
!(__r & 1); \
})
#endif
#define MUTEX_UNSET(tsl) (*(tsl) = 0)
#define MUTEX_INIT(tsl) MUTEX_UNSET(tsl)
#endif
#endif
/*********************************************************************
* S/390 32-bit assembly.
*********************************************************************/
#ifdef HAVE_MUTEX_S390_GCC_ASSEMBLY
typedef int tsl_t;
#ifdef LOAD_ACTUAL_MUTEX_CODE
/*
* For gcc/S390, 0 is clear, 1 is set.
*/
static inline int
MUTEX_SET(tsl_t *tsl) { \
register tsl_t *__l = (tsl); \
int __r; \
asm volatile( \
" la 1,%1\n" \
" lhi 0,1\n" \
" l %0,%1\n" \
"0: cs %0,0,0(1)\n" \
" jl 0b" \
: "=&d" (__r), "+m" (*__l) \
: : "0", "1", "cc"); \
return !__r; \
}
#define MUTEX_UNSET(tsl) (*(tsl) = 0)
#define MUTEX_INIT(tsl) MUTEX_UNSET(tsl)
#endif
#endif
/*********************************************************************
* SCO/cc assembly.
*********************************************************************/
#ifdef HAVE_MUTEX_SCO_X86_CC_ASSEMBLY
typedef unsigned char tsl_t;
#ifdef LOAD_ACTUAL_MUTEX_CODE
/*
* UnixWare has threads in libthread, but OpenServer doesn't (yet).
*
* For cc/x86, 0 is clear, 1 is set.
*/
#if defined(__USLC__)
asm int
_tsl_set(void *tsl)
{
%mem tsl
movl tsl, %ecx
movl $1, %eax
lock
xchgb (%ecx),%al
xorl $1,%eax
}
#endif
#define MUTEX_SET(tsl) _tsl_set(tsl)
#define MUTEX_UNSET(tsl) (*(tsl) = 0)
#define MUTEX_INIT(tsl) MUTEX_UNSET(tsl)
#endif
#endif
/*********************************************************************
* Sparc/gcc assembly.
*********************************************************************/
#ifdef HAVE_MUTEX_SPARC_GCC_ASSEMBLY
typedef unsigned char tsl_t;
#ifdef LOAD_ACTUAL_MUTEX_CODE
/*
*
* The ldstub instruction takes the location specified by its first argument
* (a register containing a memory address) and loads its contents into its
* second argument (a register) and atomically sets the contents the location
* specified by its first argument to a byte of 1s. (The value in the second
* argument is never read, but only overwritten.)
*
* The stbar is needed for v8, and is implemented as membar #sync on v9,
* so is functional there as well. For v7, stbar may generate an illegal
* instruction and we have no way to tell what we're running on. Some
* operating systems notice and skip this instruction in the fault handler.
*
* For gcc/sparc, 0 is clear, 1 is set.
*/
#define MUTEX_SET(tsl) ({ \
register tsl_t *__l = (tsl); \
register tsl_t __r; \
__asm__ volatile \
("ldstub [%1],%0; stbar" \
: "=r"( __r) : "r" (__l)); \
!__r; \
})
#define MUTEX_UNSET(tsl) (*(tsl) = 0)
#define MUTEX_INIT(tsl) MUTEX_UNSET(tsl)
#endif
#endif
/*********************************************************************
* UTS/cc assembly.
*********************************************************************/
#ifdef HAVE_MUTEX_UTS_CC_ASSEMBLY
typedef int tsl_t;
#define MUTEX_ALIGN sizeof(int)
#ifdef LOAD_ACTUAL_MUTEX_CODE
#define MUTEX_INIT(x) 0
#define MUTEX_SET(x) (!uts_lock(x, 1))
#define MUTEX_UNSET(x) (*(x) = 0)
#endif
#endif
/*********************************************************************
* x86/gcc assembly.
*********************************************************************/
#ifdef HAVE_MUTEX_X86_GCC_ASSEMBLY
typedef unsigned char tsl_t;
#ifdef LOAD_ACTUAL_MUTEX_CODE
/*
* For gcc/x86, 0 is clear, 1 is set.
*/
#define MUTEX_SET(tsl) ({ \
register tsl_t *__l = (tsl); \
int __r; \
asm volatile("movl $1,%%eax; lock; xchgb %1,%%al; xorl $1,%%eax"\
: "=&a" (__r), "=m" (*__l) \
: "1" (*__l) \
); \
__r & 1; \
})
#define MUTEX_UNSET(tsl) (*(tsl) = 0)
#define MUTEX_INIT(tsl) MUTEX_UNSET(tsl)
#endif
#endif
/*
* Mutex alignment defaults to one byte.
*
* !!!
* Various systems require different alignments for mutexes (the worst we've
* seen so far is 16-bytes on some HP architectures). Malloc(3) is assumed
* to return reasonable alignment, all other mutex users must ensure proper
* alignment locally.
*/
#ifndef MUTEX_ALIGN
#define MUTEX_ALIGN 1
#endif
/*
* Mutex destruction defaults to a no-op.
*/
#ifdef LOAD_ACTUAL_MUTEX_CODE
#ifndef MUTEX_DESTROY
#define MUTEX_DESTROY(x)
#endif
#endif
/*
* !!!
* These defines are separated into the u_int8_t flags stored in the
* mutex below, and the 32 bit flags passed to __db_mutex_setup.
* But they must co-exist and not overlap. Flags to __db_mutex_setup are:
*
* MUTEX_ALLOC - Use when the mutex to initialize needs to be allocated.
* The 'ptr' arg to __db_mutex_setup should be a DB_MUTEX ** whenever
* you use this flag. If this flag is not set, the 'ptr' arg is
* a DB_MUTEX *.
* MUTEX_NO_RECORD - Explicitly do not record the mutex in the region.
* Otherwise the mutex will be recorded by default. If you set
* this you need to understand why you don't need it recorded. The
* *only* ones not recorded are those that are part of region structures
* that only get destroyed when the regions are destroyed.
* MUTEX_NO_RLOCK - Explicitly do not lock the given region otherwise
* the region will be locked by default.
* MUTEX_SELF_BLOCK - Set if self blocking mutex.
* MUTEX_THREAD - Set if mutex is a thread-only mutex.
*/
#define MUTEX_IGNORE 0x001 /* Ignore, no lock required. */
#define MUTEX_INITED 0x002 /* Mutex is successfully initialized */
#define MUTEX_MPOOL 0x004 /* Allocated from mpool. */
#define MUTEX_SELF_BLOCK 0x008 /* Must block self. */
/* Flags only, may be larger than 0xff. */
#define MUTEX_ALLOC 0x00000100 /* Allocate and init a mutex */
#define MUTEX_NO_RECORD 0x00000200 /* Do not record lock */
#define MUTEX_NO_RLOCK 0x00000400 /* Do not acquire region lock */
#define MUTEX_THREAD 0x00000800 /* Thread-only mutex. */
/* Mutex. */
struct __mutex_t {
#ifdef HAVE_MUTEX_THREADS
#ifdef MUTEX_FIELDS
MUTEX_FIELDS
#else
tsl_t tas; /* Test and set. */
#endif
u_int32_t spins; /* Spins before block. */
u_int32_t locked; /* !0 if locked. */
#else
u_int32_t off; /* Byte offset to lock. */
u_int32_t pid; /* Lock holder: 0 or process pid. */
#endif
u_int32_t mutex_set_wait; /* Granted after wait. */
u_int32_t mutex_set_nowait; /* Granted without waiting. */
u_int32_t mutex_set_spin; /* Granted without spinning. */
u_int32_t mutex_set_spins; /* Total number of spins. */
#ifdef HAVE_MUTEX_SYSTEM_RESOURCES
roff_t reg_off; /* Shared lock info offset. */
#endif
u_int8_t flags; /* MUTEX_XXX */
};
/* Redirect calls to the correct functions. */
#ifdef HAVE_MUTEX_THREADS
#if defined(HAVE_MUTEX_PTHREADS) || \
defined(HAVE_MUTEX_SOLARIS_LWP) || \
defined(HAVE_MUTEX_UI_THREADS)
#define __db_mutex_init_int(a, b, c, d) __db_pthread_mutex_init(a, b, d)
#define __db_mutex_lock(a, b) __db_pthread_mutex_lock(a, b)
#define __db_mutex_unlock(a, b) __db_pthread_mutex_unlock(a, b)
#define __db_mutex_destroy(a) __db_pthread_mutex_destroy(a)
#elif defined(HAVE_MUTEX_WIN32)
#define __db_mutex_init_int(a, b, c, d) __db_win32_mutex_init(a, b, d)
#define __db_mutex_lock(a, b) __db_win32_mutex_lock(a, b)
#define __db_mutex_unlock(a, b) __db_win32_mutex_unlock(a, b)
#define __db_mutex_destroy(a) __db_win32_mutex_destroy(a)
#else
#define __db_mutex_init_int(a, b, c, d) __db_tas_mutex_init(a, b, d)
#define __db_mutex_lock(a, b) __db_tas_mutex_lock(a, b)
#define __db_mutex_unlock(a, b) __db_tas_mutex_unlock(a, b)
#define __db_mutex_destroy(a) __db_tas_mutex_destroy(a)
#endif
#else
#define __db_mutex_init_int(a, b, c, d) __db_fcntl_mutex_init(a, b, c)
#define __db_mutex_lock(a, b) __db_fcntl_mutex_lock(a, b)
#define __db_mutex_unlock(a, b) __db_fcntl_mutex_unlock(a, b)
#define __db_mutex_destroy(a) __db_fcntl_mutex_destroy(a)
#endif
/* Redirect system resource calls to correct functions */
#ifdef HAVE_MUTEX_SYSTEM_RESOURCES
#define __db_maintinit(a, b, c) __db_shreg_maintinit(a, b, c)
#define __db_shlocks_clear(a, b, c) __db_shreg_locks_clear(a, b, c)
#define __db_shlocks_destroy(a, b) __db_shreg_locks_destroy(a, b)
#define __db_mutex_init(a, b, c, d, e, f) \
__db_shreg_mutex_init(a, b, c, d, e, f)
#else
#define __db_maintinit(a, b, c)
#define __db_shlocks_clear(a, b, c)
#define __db_shlocks_destroy(a, b)
#define __db_mutex_init(a, b, c, d, e, f) __db_mutex_init_int(a, b, c, d)
#endif
/*
* Lock/unlock a mutex. If the mutex was marked as uninteresting, the thread
* of control can proceed without it.
*
* If the lock is for threads-only, then it was optionally not allocated and
* file handles aren't necessary, as threaded applications aren't supported by
* fcntl(2) locking.
*/
#ifdef DIAGNOSTIC
/*
* XXX
* We want to switch threads as often as possible. Yield every time
* we get a mutex to ensure contention.
*/
#define MUTEX_LOCK(dbenv, mp) \
if (!F_ISSET((mp), MUTEX_IGNORE)) \
DB_ASSERT(__db_mutex_lock(dbenv, mp) == 0); \
if (F_ISSET(dbenv, DB_ENV_YIELDCPU)) \
__os_yield(NULL, 1);
#else
#define MUTEX_LOCK(dbenv, mp) \
if (!F_ISSET((mp), MUTEX_IGNORE)) \
(void)__db_mutex_lock(dbenv, mp);
#endif
#define MUTEX_UNLOCK(dbenv, mp) \
if (!F_ISSET((mp), MUTEX_IGNORE)) \
(void)__db_mutex_unlock(dbenv, mp);
#define MUTEX_THREAD_LOCK(dbenv, mp) \
if (mp != NULL) \
MUTEX_LOCK(dbenv, mp)
#define MUTEX_THREAD_UNLOCK(dbenv, mp) \
if (mp != NULL) \
MUTEX_UNLOCK(dbenv, mp)
/*
* We use a single file descriptor for fcntl(2) locking, and (generally) the
* object's offset in a shared region as the byte that we're locking. So,
* there's a (remote) possibility that two objects might have the same offsets
* such that the locks could conflict, resulting in deadlock. To avoid this
* possibility, we offset the region offset by a small integer value, using a
* different offset for each subsystem's locks. Since all region objects are
* suitably aligned, the offset guarantees that we don't collide with another
* region's objects.
*/
#define DB_FCNTL_OFF_GEN 0 /* Everything else. */
#define DB_FCNTL_OFF_LOCK 1 /* Lock subsystem offset. */
#define DB_FCNTL_OFF_MPOOL 2 /* Mpool subsystem offset. */
#ifdef HAVE_MUTEX_SYSTEM_RESOURCES
/*
* When the underlying mutexes require library (most likely heap) or system
* resources, we have to clean up when we discard mutexes (for the library
* resources) and both when discarding mutexes and after application failure
* (for the mutexes requiring system resources). This violates the rule that
* we never look at a shared region after application failure, but we've no
* other choice. In those cases, the #define HAVE_MUTEX_SYSTEM_RESOURCES is
* set.
*
* To support mutex release after application failure, allocate thread-handle
* mutexes in shared memory instead of in the heap. The number of slots we
* allocate for this purpose isn't configurable, but this tends to be an issue
* only on embedded systems where we don't expect large server applications.
*/
#define DB_MAX_HANDLES 100 /* Mutex slots for handles. */
#endif
#endif /* !_DB_MUTEX_H_ */
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