/*- * See the file LICENSE for redistribution information. * * Copyright (c) 1996-2003 * Sleepycat Software. All rights reserved. * * $Id: mutex.h,v 1.5 2004/03/30 01:21:28 jtownsen 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; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN sizeof(int) #endif #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 /********************************************************************* * Apple/Darwin library functions. *********************************************************************/ #ifdef HAVE_MUTEX_DARWIN_SPIN_LOCK_TRY typedef u_int32_t tsl_t; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN sizeof(int) #endif #ifdef LOAD_ACTUAL_MUTEX_CODE extern int _spin_lock_try(tsl_t *); extern void _spin_unlock(tsl_t *); #define MUTEX_SET(tsl) _spin_lock_try(tsl) #define MUTEX_UNSET(tsl) _spin_unlock(tsl) #define MUTEX_INIT(tsl) (MUTEX_UNSET(tsl), 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 #ifndef MUTEX_ALIGN #define MUTEX_ALIGN 16 #endif #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; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN sizeof(int) #endif #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; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN sizeof(int) #endif #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; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN sizeof(int) #endif #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; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN sizeof(int) #endif #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 volatile unsigned char tsl_t; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN sizeof(unsigned int) #endif #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; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN sizeof(unsigned int) #endif #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; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN sizeof(unsigned int) #endif #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 *********************************************************************/ #if defined(HAVE_MUTEX_WIN32) || defined(HAVE_MUTEX_WIN32_GCC) #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) /* * From Intel's performance tuning documentation (and see SR #6975): * ftp://download.intel.com/design/perftool/cbts/appnotes/sse2/w_spinlock.pdf * * "For this reason, it is highly recommended that you insert the PAUSE * instruction into all spin-wait code immediately. Using the PAUSE * instruction does not affect the correctness of programs on existing * platforms, and it improves performance on Pentium 4 processor platforms." */ #ifdef HAVE_MUTEX_WIN32 #define MUTEX_PAUSE {__asm{_emit 0xf3}; __asm{_emit 0x90}} #endif #ifdef HAVE_MUTEX_WIN32_GCC #define MUTEX_PAUSE asm volatile ("rep; nop" : : ); #endif #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; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN 4 #endif #ifdef LOAD_ACTUAL_MUTEX_CODE /* * For gcc/alpha. Should return 0 if could not acquire the lock, 1 if * lock was acquired properly. */ 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; } #define MUTEX_INIT(tsl) MUTEX_UNSET(tsl) #endif #endif /********************************************************************* * Tru64/cc assembly. *********************************************************************/ #ifdef HAVE_MUTEX_TRU64_CC_ASSEMBLY typedef volatile u_int32_t tsl_t; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN 4 #endif #ifdef LOAD_ACTUAL_MUTEX_CODE #include <alpha/builtins.h> #define MUTEX_SET(tsl) (__LOCK_LONG_RETRY((tsl), 1) != 0) #define MUTEX_UNSET(tsl) (__UNLOCK_LONG(tsl)) #define MUTEX_INIT(tsl) (MUTEX_UNSET(tsl), 0) #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]\n\t" \ "eor %0, %0, #1\n\t" \ : "=&r" (__r) \ : "r" (1), "r" (tsl) \ ); \ __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; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN 16 #endif #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_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. */ #ifdef HAVE_MUTEX_PPC_GCC_ASSEMBLY static inline int MUTEX_SET(int *tsl) { int __r; asm volatile ( "0: \n\t" " lwarx %0,0,%1 \n\t" " cmpwi %0,0 \n\t" " bne- 1f \n\t" " stwcx. %1,0,%1 \n\t" " isync \n\t" " beq+ 2f \n\t" " b 0b \n\t" "1: \n\t" " li %1, 0 \n\t" "2: \n\t" : "=&r" (__r), "+r" (tsl) : : "cr0", "memory"); return (int)tsl; } #endif static inline int MUTEX_UNSET(tsl_t *tsl) { asm volatile("sync" : : : "memory"); return *tsl = 0; } #define MUTEX_INIT(tsl) MUTEX_UNSET(tsl) #endif #endif /********************************************************************* * OS/390 C *********************************************************************/ #ifdef HAVE_MUTEX_S390_CC_ASSEMBLY typedef int tsl_t; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN sizeof(int) #endif #ifdef LOAD_ACTUAL_MUTEX_CODE /* * cs() is declared in <stdlib.h> but is built in to the compiler. * Must use LANGLVL(EXTENDED) to get its declaration. */ #define MUTEX_SET(tsl) (!cs(&zero, (tsl), 1)) #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; #ifndef MUTEX_ALIGN #define MUTEX_ALIGN sizeof(int) #endif #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) /* * From Intel's performance tuning documentation (and see SR #6975): * ftp://download.intel.com/design/perftool/cbts/appnotes/sse2/w_spinlock.pdf * * "For this reason, it is highly recommended that you insert the PAUSE * instruction into all spin-wait code immediately. Using the PAUSE * instruction does not affect the correctness of programs on existing * platforms, and it improves performance on Pentium 4 processor platforms." */ #define MUTEX_PAUSE asm volatile ("rep; nop" : : ); #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 /* * !!! * The flag arguments for __db_mutex_setup (and the underyling intialization * function for the mutex type, for example, __db_tas_mutex_init), and flags * stored in the DB_MUTEX structure are combined, and may not overlap. Flags * to __db_mutex_setup: * * 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_ALLOC 0x0001 /* Allocate and init a mutex */ #define MUTEX_IGNORE 0x0002 /* Ignore, no lock required. */ #define MUTEX_INITED 0x0004 /* Mutex is successfully initialized */ #define MUTEX_LOGICAL_LOCK 0x0008 /* Mutex backs database lock. */ #define MUTEX_MPOOL 0x0010 /* Allocated from mpool. */ #define MUTEX_NO_RECORD 0x0020 /* Do not record lock */ #define MUTEX_NO_RLOCK 0x0040 /* Do not acquire region lock */ #define MUTEX_SELF_BLOCK 0x0080 /* Must block self. */ #define MUTEX_THREAD 0x0100 /* 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 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 /* * Flags should be an unsigned integer even if it's not required by * the possible flags values, getting a single byte on some machines * is expensive, and the mutex structure is a MP hot spot. */ u_int32_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) || defined(HAVE_MUTEX_WIN32_GCC) #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_ */