/****************************************************** The interface to the operating system file i/o primitives (c) 1995 Innobase Oy Created 10/21/1995 Heikki Tuuri *******************************************************/ #include "os0file.h" #include "os0sync.h" #include "ut0mem.h" #include "srv0srv.h" #include "trx0sys.h" #undef HAVE_FDATASYNC #ifdef POSIX_ASYNC_IO /* We assume in this case that the OS has standard Posix aio (at least SunOS 2.6, HP-UX 11i and AIX 4.3 have) */ #endif /* We use these mutexes to protect lseek + file i/o operation, if the OS does not provide an atomic pread or pwrite, or similar */ #define OS_FILE_N_SEEK_MUTEXES 16 os_mutex_t os_file_seek_mutexes[OS_FILE_N_SEEK_MUTEXES]; /* In simulated aio, merge at most this many consecutive i/os */ #define OS_AIO_MERGE_N_CONSECUTIVE 32 /* If this flag is TRUE, then we will use the native aio of the OS (provided we compiled Innobase with it in), otherwise we will use simulated aio we build below with threads */ ibool os_aio_use_native_aio = FALSE; /* The aio array slot structure */ typedef struct os_aio_slot_struct os_aio_slot_t; struct os_aio_slot_struct{ ibool is_read; /* TRUE if a read operation */ ulint pos; /* index of the slot in the aio array */ ibool reserved; /* TRUE if this slot is reserved */ ulint len; /* length of the block to read or write */ byte* buf; /* buffer used in i/o */ ulint type; /* OS_FILE_READ or OS_FILE_WRITE */ ulint offset; /* 32 low bits of file offset in bytes */ ulint offset_high; /* 32 high bits of file offset */ os_file_t file; /* file where to read or write */ char* name; /* file name or path */ ibool io_already_done;/* used only in simulated aio: TRUE if the physical i/o already made and only the slot message needs to be passed to the caller of os_aio_simulated_handle */ void* message1; /* message which is given by the */ void* message2; /* the requester of an aio operation and which can be used to identify which pending aio operation was completed */ #ifdef WIN_ASYNC_IO OVERLAPPED control; /* Windows control block for the aio request */ #elif defined(POSIX_ASYNC_IO) struct aiocb control; /* Posix control block for aio request */ #endif }; /* The aio array structure */ typedef struct os_aio_array_struct os_aio_array_t; struct os_aio_array_struct{ os_mutex_t mutex; /* the mutex protecting the aio array */ os_event_t not_full; /* The event which is set to the signaled state when there is space in the aio outside the ibuf segment */ os_event_t is_empty; /* The event which is set to the signaled state when there are no pending i/os in this array */ ulint n_slots; /* Total number of slots in the aio array. This must be divisible by n_threads. */ ulint n_segments;/* Number of segments in the aio array of pending aio requests. A thread can wait separately for any one of the segments. */ ulint n_reserved;/* Number of reserved slots in the aio array outside the ibuf segment */ os_aio_slot_t* slots; /* Pointer to the slots in the array */ os_event_t* events; /* Pointer to an array of event handles where we copied the handles from slots, in the same order. This can be used in WaitForMultipleObjects; used only in Windows */ }; /* Array of events used in simulated aio */ os_event_t* os_aio_segment_wait_events = NULL; /* The aio arrays for non-ibuf i/o and ibuf i/o, as well as sync aio. These are NULL when the module has not yet been initialized. */ os_aio_array_t* os_aio_read_array = NULL; os_aio_array_t* os_aio_write_array = NULL; os_aio_array_t* os_aio_ibuf_array = NULL; os_aio_array_t* os_aio_log_array = NULL; os_aio_array_t* os_aio_sync_array = NULL; ulint os_aio_n_segments = ULINT_UNDEFINED; /*************************************************************************** Gets the operating system version. Currently works only on Windows. */ ulint os_get_os_version(void) /*===================*/ /* out: OS_WIN95, OS_WIN31, OS_WINNT (2000 == NT) */ { #ifdef __WIN__ OSVERSIONINFO os_info; os_info.dwOSVersionInfoSize = sizeof(OSVERSIONINFO); ut_a(GetVersionEx(&os_info)); if (os_info.dwPlatformId == VER_PLATFORM_WIN32s) { return(OS_WIN31); } else if (os_info.dwPlatformId == VER_PLATFORM_WIN32_WINDOWS) { return(OS_WIN95); } else if (os_info.dwPlatformId == VER_PLATFORM_WIN32_NT) { return(OS_WINNT); } else { ut_error; return(0); } #else ut_error; return(0); #endif } /*************************************************************************** Retrieves the last error number if an error occurs in a file io function. The number should be retrieved before any other OS calls (because they may overwrite the error number). If the number is not known to this program, the OS error number + 100 is returned. */ ulint os_file_get_last_error(void) /*========================*/ /* out: error number, or OS error number + 100 */ { ulint err; #ifdef __WIN__ err = (ulint) GetLastError(); if (err != ERROR_FILE_EXISTS) { fprintf(stderr, "InnoDB: operating system error number %li in a file operation.\n", (long) err); } if (err == ERROR_FILE_NOT_FOUND) { return(OS_FILE_NOT_FOUND); } else if (err == ERROR_DISK_FULL) { return(OS_FILE_DISK_FULL); } else if (err == ERROR_FILE_EXISTS) { return(OS_FILE_ALREADY_EXISTS); } else { return(100 + err); } #else err = (ulint) errno; if (err != EEXIST) { fprintf(stderr, "InnoDB: operating system error number %i in a file operation.\n", errno); } if (err == ENOSPC ) { return(OS_FILE_DISK_FULL); #ifdef POSIX_ASYNC_IO } else if (err == EAGAIN) { return(OS_FILE_AIO_RESOURCES_RESERVED); #endif } else if (err == ENOENT) { return(OS_FILE_NOT_FOUND); } else if (err == EEXIST) { return(OS_FILE_ALREADY_EXISTS); } else { return(100 + err); } #endif } /******************************************************************** Does error handling when a file operation fails. If we have run out of disk space, then the user can clean the disk. If we do not find a specified file, then the user can copy it to disk. */ static ibool os_file_handle_error( /*=================*/ /* out: TRUE if we should retry the operation */ os_file_t file, /* in: file pointer */ char* name) /* in: name of a file or NULL */ { ulint err; UT_NOT_USED(file); err = os_file_get_last_error(); if (err == OS_FILE_DISK_FULL) { fprintf(stderr, "\n"); if (name) { fprintf(stderr, "InnoDB: Encountered a problem with file %s.\n", name); } fprintf(stderr, "InnoDB: Cannot continue operation.\n" "InnoDB: Disk is full. Try to clean the disk to free space.\n" "InnoDB: Delete possible created file and restart.\n"); exit(1); } else if (err == OS_FILE_AIO_RESOURCES_RESERVED) { return(TRUE); } else { fprintf(stderr, "InnoDB: Cannot continue operation.\n"); exit(1); } return(FALSE); } /******************************************************************** Opens an existing file or creates a new. */ os_file_t os_file_create( /*===========*/ /* out, own: handle to the file, not defined if error, error number can be retrieved with os_get_last_error */ char* name, /* in: name of the file or path as a null-terminated string */ ulint create_mode, /* in: OS_FILE_OPEN if an existing file is opened (if does not exist, error), or OS_FILE_CREATE if a new file is created (if exists, error), OS_FILE_OVERWRITE if a new is created or an old overwritten */ ulint purpose,/* in: OS_FILE_AIO, if asynchronous, non-buffered i/o is desired, OS_FILE_NORMAL, if any normal file */ ulint type, /* in: OS_DATA_FILE or OS_LOG_FILE */ ibool* success)/* out: TRUE if succeed, FALSE if error */ { #ifdef __WIN__ os_file_t file; DWORD create_flag; DWORD attributes; ibool retry; try_again: ut_a(name); if (create_mode == OS_FILE_OPEN) { create_flag = OPEN_EXISTING; } else if (create_mode == OS_FILE_CREATE) { create_flag = CREATE_NEW; } else if (create_mode == OS_FILE_OVERWRITE) { create_flag = CREATE_ALWAYS; } else { create_flag = 0; ut_error; } if (purpose == OS_FILE_AIO) { /* use asynchronous (overlapped) io and no buffering of writes in the OS */ attributes = 0; #ifdef WIN_ASYNC_IO if (os_aio_use_native_aio) { attributes = attributes | FILE_FLAG_OVERLAPPED; } #endif #ifdef UNIV_NON_BUFFERED_IO attributes = attributes | FILE_FLAG_NO_BUFFERING; #endif } else if (purpose == OS_FILE_NORMAL) { attributes = 0 #ifdef UNIV_NON_BUFFERED_IO | FILE_FLAG_NO_BUFFERING #endif ; } else { attributes = 0; ut_error; } file = CreateFile(name, GENERIC_READ | GENERIC_WRITE, /* read and write access */ FILE_SHARE_READ,/* file can be read by other processes */ NULL, /* default security attributes */ create_flag, attributes, NULL); /* no template file */ if (file == INVALID_HANDLE_VALUE) { *success = FALSE; if (create_mode != OS_FILE_OPEN && os_file_get_last_error() == OS_FILE_DISK_FULL) { retry = os_file_handle_error(file, name); if (retry) { goto try_again; } } } else { *success = TRUE; } return(file); #else os_file_t file; int create_flag; ibool retry; try_again: ut_a(name); if (create_mode == OS_FILE_OPEN) { create_flag = O_RDWR; } else if (create_mode == OS_FILE_CREATE) { create_flag = O_RDWR | O_CREAT | O_EXCL; } else if (create_mode == OS_FILE_OVERWRITE) { create_flag = O_RDWR | O_CREAT | O_TRUNC; } else { create_flag = 0; ut_error; } UT_NOT_USED(purpose); #ifdef O_SYNC if ((!srv_use_doublewrite_buf || type != OS_DATA_FILE) && srv_unix_file_flush_method == SRV_UNIX_O_DSYNC) { create_flag = create_flag | O_SYNC; } #endif if (create_mode == OS_FILE_CREATE) { file = open(name, create_flag, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH); } else { file = open(name, create_flag); } if (file == -1) { *success = FALSE; if (create_mode != OS_FILE_OPEN && errno == ENOSPC) { retry = os_file_handle_error(file, name); if (retry) { goto try_again; } } } else { *success = TRUE; } return(file); #endif } /*************************************************************************** Closes a file handle. In case of error, error number can be retrieved with os_file_get_last_error. */ ibool os_file_close( /*==========*/ /* out: TRUE if success */ os_file_t file) /* in, own: handle to a file */ { #ifdef __WIN__ BOOL ret; ut_a(file); ret = CloseHandle(file); if (ret) { return(TRUE); } return(FALSE); #else int ret; ret = close(file); if (ret == -1) { return(FALSE); } return(TRUE); #endif } /*************************************************************************** Gets a file size. */ ibool os_file_get_size( /*=============*/ /* out: TRUE if success */ os_file_t file, /* in: handle to a file */ ulint* size, /* out: least significant 32 bits of file size */ ulint* size_high)/* out: most significant 32 bits of size */ { #ifdef __WIN__ DWORD high; DWORD low; low = GetFileSize(file, &high); if ((low == 0xFFFFFFFF) && (GetLastError() != NO_ERROR)) { return(FALSE); } *size = low; *size_high = high; return(TRUE); #else *size = (ulint) lseek(file, 0, SEEK_END); *size_high = 0; return(TRUE); #endif } /*************************************************************************** Sets a file size. This function can be used to extend or truncate a file. */ ibool os_file_set_size( /*=============*/ /* out: TRUE if success */ char* name, /* in: name of the file or path as a null-terminated string */ os_file_t file, /* in: handle to a file */ ulint size, /* in: least significant 32 bits of file size */ ulint size_high)/* in: most significant 32 bits of size */ { ulint offset; ulint n_bytes; ulint low; ibool ret; ibool retry; ulint i; byte* buf; try_again: /* We use a very big 8 MB buffer in writing because Linux may be extremely slow in fdatasync on 1 MB writes */ buf = ut_malloc(UNIV_PAGE_SIZE * 512); /* Write buffer full of zeros */ for (i = 0; i < UNIV_PAGE_SIZE * 512; i++) { buf[i] = '\0'; } offset = 0; low = size; #if (UNIV_WORD_SIZE == 8) low = low + (size_high << 32); #else UT_NOT_USED(size_high); #endif while (offset < low) { if (low - offset < UNIV_PAGE_SIZE * 512) { n_bytes = low - offset; } else { n_bytes = UNIV_PAGE_SIZE * 512; } ret = os_file_write(name, file, buf, offset, 0, n_bytes); if (!ret) { ut_free(buf); goto error_handling; } offset += n_bytes; } ut_free(buf); ret = os_file_flush(file); if (ret) { return(TRUE); } error_handling: retry = os_file_handle_error(file, name); if (retry) { goto try_again; } ut_error; return(FALSE); } /*************************************************************************** Flushes the write buffers of a given file to the disk. */ ibool os_file_flush( /*==========*/ /* out: TRUE if success */ os_file_t file) /* in, own: handle to a file */ { #ifdef __WIN__ BOOL ret; ut_a(file); ret = FlushFileBuffers(file); if (ret) { return(TRUE); } return(FALSE); #else int ret; #ifdef HAVE_FDATASYNC ret = fdatasync(file); #else ret = fsync(file); #endif if (ret == 0) { return(TRUE); } fprintf(stderr, "InnoDB: Error: the OS said file flush did not succeed\n"); os_file_handle_error(file, NULL); return(FALSE); #endif } #ifndef __WIN__ /*********************************************************************** Does a synchronous read operation in Posix. */ static ssize_t os_file_pread( /*==========*/ /* out: number of bytes read, -1 if error */ os_file_t file, /* in: handle to a file */ void* buf, /* in: buffer where to read */ ulint n, /* in: number of bytes to read */ ulint offset) /* in: offset from where to read */ { off_t offs = (off_t)offset; #ifdef HAVE_PREAD return(pread(file, buf, n, offs)); #else ssize_t ret; ulint i; /* Protect the seek / read operation with a mutex */ i = ((ulint) file) % OS_FILE_N_SEEK_MUTEXES; os_mutex_enter(os_file_seek_mutexes[i]); ret = lseek(file, offs, 0); if (ret < 0) { os_mutex_exit(os_file_seek_mutexes[i]); return(ret); } ret = read(file, buf, n); os_mutex_exit(os_file_seek_mutexes[i]); return(ret); #endif } /*********************************************************************** Does a synchronous write operation in Posix. */ static ssize_t os_file_pwrite( /*===========*/ /* out: number of bytes written, -1 if error */ os_file_t file, /* in: handle to a file */ void* buf, /* in: buffer from where to write */ ulint n, /* in: number of bytes to write */ ulint offset) /* in: offset where to write */ { ssize_t ret; off_t offs = (off_t)offset; #ifdef HAVE_PWRITE ret = pwrite(file, buf, n, offs); if (srv_unix_file_flush_method != SRV_UNIX_LITTLESYNC && srv_unix_file_flush_method != SRV_UNIX_NOSYNC && !trx_doublewrite) { /* Always do fsync to reduce the probability that when the OS crashes, a database page is only partially physically written to disk. */ ut_a(TRUE == os_file_flush(file)); } return(ret); #else ulint i; /* Protect the seek / write operation with a mutex */ i = ((ulint) file) % OS_FILE_N_SEEK_MUTEXES; os_mutex_enter(os_file_seek_mutexes[i]); ret = lseek(file, offs, 0); if (ret < 0) { os_mutex_exit(os_file_seek_mutexes[i]); return(ret); } ret = write(file, buf, n); if (srv_unix_file_flush_method != SRV_UNIX_LITTLESYNC && srv_unix_file_flush_method != SRV_UNIX_NOSYNC && !trx_doublewrite) { /* Always do fsync to reduce the probability that when the OS crashes, a database page is only partially physically written to disk. */ ut_a(TRUE == os_file_flush(file)); } os_mutex_exit(os_file_seek_mutexes[i]); return(ret); #endif } #endif /*********************************************************************** Requests a synchronous positioned read operation. */ ibool os_file_read( /*=========*/ /* out: TRUE if request was successful, FALSE if fail */ os_file_t file, /* in: handle to a file */ void* buf, /* in: buffer where to read */ ulint offset, /* in: least significant 32 bits of file offset where to read */ ulint offset_high, /* in: most significant 32 bits of offset */ ulint n) /* in: number of bytes to read */ { #ifdef __WIN__ BOOL ret; DWORD len; DWORD ret2; DWORD err; DWORD low; DWORD high; ibool retry; ulint i; try_again: ut_ad(file); ut_ad(buf); ut_ad(n > 0); low = offset; high = offset_high; /* Protect the seek / read operation with a mutex */ i = ((ulint) file) % OS_FILE_N_SEEK_MUTEXES; os_mutex_enter(os_file_seek_mutexes[i]); ret2 = SetFilePointer(file, low, &high, FILE_BEGIN); if (ret2 == 0xFFFFFFFF && GetLastError() != NO_ERROR) { err = GetLastError(); os_mutex_exit(os_file_seek_mutexes[i]); goto error_handling; } ret = ReadFile(file, buf, n, &len, NULL); os_mutex_exit(os_file_seek_mutexes[i]); if (ret && len == n) { return(TRUE); } err = GetLastError(); #else ibool retry; ssize_t ret; #if (UNIV_WORD_SIZE == 8) offset = offset + (offset_high << 32); #else UT_NOT_USED(offset_high); #endif try_again: ret = os_file_pread(file, buf, n, offset); if ((ulint)ret == n) { return(TRUE); } #endif error_handling: retry = os_file_handle_error(file, NULL); if (retry) { goto try_again; } ut_error; return(FALSE); } /*********************************************************************** Requests a synchronous write operation. */ ibool os_file_write( /*==========*/ /* out: TRUE if request was successful, FALSE if fail */ char* name, /* in: name of the file or path as a null-terminated string */ os_file_t file, /* in: handle to a file */ void* buf, /* in: buffer from which to write */ ulint offset, /* in: least significant 32 bits of file offset where to write */ ulint offset_high, /* in: most significant 32 bits of offset */ ulint n) /* in: number of bytes to write */ { #ifdef __WIN__ BOOL ret; DWORD len; DWORD ret2; DWORD err; DWORD low; DWORD high; ibool retry; ulint i; try_again: ut_ad(file); ut_ad(buf); ut_ad(n > 0); low = offset; high = offset_high; /* Protect the seek / write operation with a mutex */ i = ((ulint) file) % OS_FILE_N_SEEK_MUTEXES; os_mutex_enter(os_file_seek_mutexes[i]); ret2 = SetFilePointer(file, low, &high, FILE_BEGIN); if (ret2 == 0xFFFFFFFF && GetLastError() != NO_ERROR) { err = GetLastError(); os_mutex_exit(os_file_seek_mutexes[i]); goto error_handling; } ret = WriteFile(file, buf, n, &len, NULL); /* Always do fsync to reduce the probability that when the OS crashes, a database page is only partially physically written to disk. */ if (!trx_doublewrite) { ut_a(TRUE == os_file_flush(file)); } os_mutex_exit(os_file_seek_mutexes[i]); if (ret && len == n) { return(TRUE); } #else ibool retry; ssize_t ret; #if (UNIV_WORD_SIZE == 8) offset = offset + (offset_high << 32); #else UT_NOT_USED(offset_high); #endif try_again: ret = os_file_pwrite(file, buf, n, offset); if ((ulint)ret == n) { return(TRUE); } #endif error_handling: retry = os_file_handle_error(file, name); if (retry) { goto try_again; } ut_error; return(FALSE); } /******************************************************************** Returns a pointer to the nth slot in the aio array. */ static os_aio_slot_t* os_aio_array_get_nth_slot( /*======================*/ /* out: pointer to slot */ os_aio_array_t* array, /* in: aio array */ ulint index) /* in: index of the slot */ { ut_a(index < array->n_slots); return((array->slots) + index); } /**************************************************************************** Creates an aio wait array. */ static os_aio_array_t* os_aio_array_create( /*================*/ /* out, own: aio array */ ulint n, /* in: maximum number of pending aio operations allowed; n must be divisible by n_segments */ ulint n_segments) /* in: number of segments in the aio array */ { os_aio_array_t* array; ulint i; os_aio_slot_t* slot; #ifdef WIN_ASYNC_IO OVERLAPPED* over; #endif ut_a(n > 0); ut_a(n_segments > 0); ut_a(n % n_segments == 0); array = ut_malloc(sizeof(os_aio_array_t)); array->mutex = os_mutex_create(NULL); array->not_full = os_event_create(NULL); array->is_empty = os_event_create(NULL); os_event_set(array->is_empty); array->n_slots = n; array->n_segments = n_segments; array->n_reserved = 0; array->slots = ut_malloc(n * sizeof(os_aio_slot_t)); array->events = ut_malloc(n * sizeof(os_event_t)); for (i = 0; i < n; i++) { slot = os_aio_array_get_nth_slot(array, i); slot->pos = i; slot->reserved = FALSE; #ifdef WIN_ASYNC_IO over = &(slot->control); over->hEvent = os_event_create(NULL); *((array->events) + i) = over->hEvent; #endif } return(array); } /**************************************************************************** Initializes the asynchronous io system. Creates separate aio array for non-ibuf read and write, a third aio array for the ibuf i/o, with just one segment, two aio arrays for log reads and writes with one segment, and a synchronous aio array of the specified size. The combined number of segments in the three first aio arrays is the parameter n_segments given to the function. The caller must create an i/o handler thread for each segment in the four first arrays, but not for the sync aio array. */ void os_aio_init( /*========*/ ulint n, /* in: maximum number of pending aio operations allowed; n must be divisible by n_segments */ ulint n_segments, /* in: combined number of segments in the four first aio arrays; must be >= 4 */ ulint n_slots_sync) /* in: number of slots in the sync aio array */ { ulint n_read_segs; ulint n_write_segs; ulint n_per_seg; ulint i; #ifdef POSIX_ASYNC_IO sigset_t sigset; #endif ut_ad(n % n_segments == 0); ut_ad(n_segments >= 4); n_per_seg = n / n_segments; n_write_segs = (n_segments - 2) / 2; n_read_segs = n_segments - 2 - n_write_segs; /* printf("Array n per seg %lu\n", n_per_seg); */ os_aio_read_array = os_aio_array_create(n_read_segs * n_per_seg, n_read_segs); os_aio_write_array = os_aio_array_create(n_write_segs * n_per_seg, n_write_segs); os_aio_ibuf_array = os_aio_array_create(n_per_seg, 1); os_aio_log_array = os_aio_array_create(n_per_seg, 1); os_aio_sync_array = os_aio_array_create(n_slots_sync, 1); os_aio_n_segments = n_segments; os_aio_validate(); for (i = 0; i < OS_FILE_N_SEEK_MUTEXES; i++) { os_file_seek_mutexes[i] = os_mutex_create(NULL); } os_aio_segment_wait_events = ut_malloc(n_segments * sizeof(void*)); for (i = 0; i < n_segments; i++) { os_aio_segment_wait_events[i] = os_event_create(NULL); } #ifdef POSIX_ASYNC_IO /* Block aio signals from the current thread and its children: for this to work, the current thread must be the first created in the database, so that all its children will inherit its signal mask */ /* TODO: to work MySQL needs the SIGALARM signal; the following will not work yet! */ sigemptyset(&sigset); sigaddset(&sigset, SIGRTMIN + 1 + 0); sigaddset(&sigset, SIGRTMIN + 1 + 1); sigaddset(&sigset, SIGRTMIN + 1 + 2); sigaddset(&sigset, SIGRTMIN + 1 + 3); pthread_sigmask(SIG_BLOCK, &sigset, NULL); */ #endif } /**************************************************************************** Waits until there are no pending writes in os_aio_write_array. There can be other, synchronous, pending writes. */ void os_aio_wait_until_no_pending_writes(void) /*=====================================*/ { os_event_wait(os_aio_write_array->is_empty); } /************************************************************************** Calculates segment number for a slot. */ static ulint os_aio_get_segment_no_from_slot( /*============================*/ /* out: segment number (which is the number used by, for example, i/o-handler threads) */ os_aio_array_t* array, /* in: aio wait array */ os_aio_slot_t* slot) /* in: slot in this array */ { ulint segment; ulint seg_len; if (array == os_aio_ibuf_array) { segment = 0; } else if (array == os_aio_log_array) { segment = 1; } else if (array == os_aio_read_array) { seg_len = os_aio_read_array->n_slots / os_aio_read_array->n_segments; segment = 2 + slot->pos / seg_len; } else { ut_a(array == os_aio_write_array); seg_len = os_aio_write_array->n_slots / os_aio_write_array->n_segments; segment = os_aio_read_array->n_segments + 2 + slot->pos / seg_len; } return(segment); } /************************************************************************** Calculates local segment number and aio array from global segment number. */ static ulint os_aio_get_array_and_local_segment( /*===============================*/ /* out: local segment number within the aio array */ os_aio_array_t** array, /* out: aio wait array */ ulint global_segment)/* in: global segment number */ { ulint segment; ut_a(global_segment < os_aio_n_segments); if (global_segment == 0) { *array = os_aio_ibuf_array; segment = 0; } else if (global_segment == 1) { *array = os_aio_log_array; segment = 0; } else if (global_segment < os_aio_read_array->n_segments + 2) { *array = os_aio_read_array; segment = global_segment - 2; } else { *array = os_aio_write_array; segment = global_segment - (os_aio_read_array->n_segments + 2); } return(segment); } /*********************************************************************** Gets an integer value designating a specified aio array. This is used to give numbers to signals in Posix aio. */ static ulint os_aio_get_array_no( /*================*/ os_aio_array_t* array) /* in: aio array */ { if (array == os_aio_ibuf_array) { return(0); } else if (array == os_aio_log_array) { return(1); } else if (array == os_aio_read_array) { return(2); } else if (array == os_aio_write_array) { return(3); } else { ut_a(0); return(0); } } /*********************************************************************** Gets the aio array for its number. */ static os_aio_array_t* os_aio_get_array_from_no( /*=====================*/ /* out: aio array */ ulint n) /* in: array number */ { if (n == 0) { return(os_aio_ibuf_array); } else if (n == 1) { return(os_aio_log_array); } else if (n == 2) { return(os_aio_read_array); } else if (n == 3) { return(os_aio_write_array); } else { ut_a(0); return(NULL); } } /*********************************************************************** Requests for a slot in the aio array. If no slot is available, waits until not_full-event becomes signaled. */ static os_aio_slot_t* os_aio_array_reserve_slot( /*======================*/ /* out: pointer to slot */ ulint type, /* in: OS_FILE_READ or OS_FILE_WRITE */ os_aio_array_t* array, /* in: aio array */ void* message1,/* in: message to be passed along with the aio operation */ void* message2,/* in: message to be passed along with the aio operation */ os_file_t file, /* in: file handle */ char* name, /* in: name of the file or path as a null-terminated string */ void* buf, /* in: buffer where to read or from which to write */ ulint offset, /* in: least significant 32 bits of file offset */ ulint offset_high, /* in: most significant 32 bits of offset */ ulint len) /* in: length of the block to read or write */ { os_aio_slot_t* slot; #ifdef WIN_ASYNC_IO OVERLAPPED* control; #elif defined(POSIX_ASYNC_IO) struct aiocb* control; #endif ulint i; loop: os_mutex_enter(array->mutex); if (array->n_reserved == array->n_slots) { os_mutex_exit(array->mutex); if (!os_aio_use_native_aio) { /* If the handler threads are suspended, wake them so that we get more slots */ os_aio_simulated_wake_handler_threads(); } os_event_wait(array->not_full); goto loop; } for (i = 0;; i++) { slot = os_aio_array_get_nth_slot(array, i); if (slot->reserved == FALSE) { break; } } array->n_reserved++; if (array->n_reserved == 1) { os_event_reset(array->is_empty); } if (array->n_reserved == array->n_slots) { os_event_reset(array->not_full); } slot->reserved = TRUE; slot->message1 = message1; slot->message2 = message2; slot->file = file; slot->name = name; slot->len = len; slot->type = type; slot->buf = buf; slot->offset = offset; slot->offset_high = offset_high; slot->io_already_done = FALSE; #ifdef WIN_ASYNC_IO control = &(slot->control); control->Offset = (DWORD)offset; control->OffsetHigh = (DWORD)offset_high; os_event_reset(control->hEvent); #elif defined(POSIX_ASYNC_IO) #if (UNIV_WORD_SIZE == 8) offset = offset + (offset_high << 32); #else ut_a(offset_high == 0); #endif control = &(slot->control); control->aio_fildes = file; control->aio_buf = buf; control->aio_nbytes = len; control->aio_offset = offset; control->aio_reqprio = 0; control->aio_sigevent.sigev_notify = SIGEV_SIGNAL; control->aio_sigevent.sigev_signo = SIGRTMIN + 1 + os_aio_get_array_no(array); /* TODO: How to choose the signal numbers? */ /* printf("AIO signal number %lu\n", (ulint) control->aio_sigevent.sigev_signo); */ control->aio_sigevent.sigev_value.sival_ptr = slot; #endif os_mutex_exit(array->mutex); return(slot); } /*********************************************************************** Frees a slot in the aio array. */ static void os_aio_array_free_slot( /*===================*/ os_aio_array_t* array, /* in: aio array */ os_aio_slot_t* slot) /* in: pointer to slot */ { ut_ad(array); ut_ad(slot); os_mutex_enter(array->mutex); ut_ad(slot->reserved); slot->reserved = FALSE; array->n_reserved--; if (array->n_reserved == array->n_slots - 1) { os_event_set(array->not_full); } if (array->n_reserved == 0) { os_event_set(array->is_empty); } #ifdef WIN_ASYNC_IO os_event_reset(slot->control.hEvent); #endif os_mutex_exit(array->mutex); } /************************************************************************** Wakes up a simulated aio i/o-handler thread if it has something to do. */ static void os_aio_simulated_wake_handler_thread( /*=================================*/ ulint global_segment) /* in: the number of the segment in the aio arrays */ { os_aio_array_t* array; ulint segment; os_aio_slot_t* slot; ulint n; ulint i; ut_ad(!os_aio_use_native_aio); segment = os_aio_get_array_and_local_segment(&array, global_segment); n = array->n_slots / array->n_segments; /* Look through n slots after the segment * n'th slot */ os_mutex_enter(array->mutex); for (i = 0; i < n; i++) { slot = os_aio_array_get_nth_slot(array, i + segment * n); if (slot->reserved) { /* Found an i/o request */ break; } } os_mutex_exit(array->mutex); if (i < n) { os_event_set(os_aio_segment_wait_events[global_segment]); } } /************************************************************************** Wakes up simulated aio i/o-handler threads if they have something to do. */ void os_aio_simulated_wake_handler_threads(void) /*=======================================*/ { ulint i; if (os_aio_use_native_aio) { /* We do not use simulated aio: do nothing */ return; } for (i = 0; i < os_aio_n_segments; i++) { os_aio_simulated_wake_handler_thread(i); } } /*********************************************************************** Requests an asynchronous i/o operation. */ ibool os_aio( /*===*/ /* out: TRUE if request was queued successfully, FALSE if fail */ ulint type, /* in: OS_FILE_READ or OS_FILE_WRITE */ ulint mode, /* in: OS_AIO_NORMAL, ..., possibly ORed to OS_AIO_SIMULATED_WAKE_LATER: the last flag advises this function not to wake i/o-handler threads, but the caller will do the waking explicitly later, in this way the caller can post several requests in a batch; NOTE that the batch must not be so big that it exhausts the slots in aio arrays! NOTE that a simulated batch may introduce hidden chances of deadlocks, because i/os are not actually handled until all have been posted: use with great caution! */ char* name, /* in: name of the file or path as a null-terminated string */ os_file_t file, /* in: handle to a file */ void* buf, /* in: buffer where to read or from which to write */ ulint offset, /* in: least significant 32 bits of file offset where to read or write */ ulint offset_high, /* in: most significant 32 bits of offset */ ulint n, /* in: number of bytes to read or write */ void* message1,/* in: messages for the aio handler (these can be used to identify a completed aio operation); if mode is OS_AIO_SYNC, these are ignored */ void* message2) { os_aio_array_t* array; os_aio_slot_t* slot; #ifdef WIN_ASYNC_IO BOOL ret = TRUE; DWORD len = n; void* dummy_mess1; void* dummy_mess2; ulint dummy_type; #endif ulint err = 0; ibool retry; ulint wake_later; ut_ad(file); ut_ad(buf); ut_ad(n > 0); ut_ad(n % OS_FILE_LOG_BLOCK_SIZE == 0); ut_ad((ulint)buf % OS_FILE_LOG_BLOCK_SIZE == 0) ut_ad(offset % OS_FILE_LOG_BLOCK_SIZE == 0); ut_ad(os_aio_validate()); wake_later = mode & OS_AIO_SIMULATED_WAKE_LATER; mode = mode & (~OS_AIO_SIMULATED_WAKE_LATER); if (mode == OS_AIO_SYNC #ifdef WIN_ASYNC_IO && !os_aio_use_native_aio #endif ) { /* This is actually an ordinary synchronous read or write: no need to use an i/o-handler thread. NOTE that if we use Windows async i/o, Windows does not allow us to use ordinary synchronous os_file_read etc. on the same file, therefore we have built a special mechanism for synchronous wait in the Windows case. */ if (type == OS_FILE_READ) { return(os_file_read(file, buf, offset, offset_high, n)); } ut_a(type == OS_FILE_WRITE); return(os_file_write(name, file, buf, offset, offset_high, n)); } try_again: if (mode == OS_AIO_NORMAL) { if (type == OS_FILE_READ) { array = os_aio_read_array; } else { array = os_aio_write_array; } } else if (mode == OS_AIO_IBUF) { ut_ad(type == OS_FILE_READ); /* Reduce probability of deadlock bugs in connection with ibuf: do not let the ibuf i/o handler sleep */ wake_later = FALSE; array = os_aio_ibuf_array; } else if (mode == OS_AIO_LOG) { array = os_aio_log_array; } else if (mode == OS_AIO_SYNC) { array = os_aio_sync_array; } else { ut_error; } slot = os_aio_array_reserve_slot(type, array, message1, message2, file, name, buf, offset, offset_high, n); if (type == OS_FILE_READ) { if (os_aio_use_native_aio) { #ifdef WIN_ASYNC_IO ret = ReadFile(file, buf, (DWORD)n, &len, &(slot->control)); #elif defined(POSIX_ASYNC_IO) slot->control.aio_lio_opcode = LIO_READ; err = (ulint) aio_read(&(slot->control)); printf("Starting Posix aio read %lu\n", err); #endif } else { if (!wake_later) { os_aio_simulated_wake_handler_thread( os_aio_get_segment_no_from_slot(array, slot)); } } } else if (type == OS_FILE_WRITE) { if (os_aio_use_native_aio) { #ifdef WIN_ASYNC_IO ret = WriteFile(file, buf, (DWORD)n, &len, &(slot->control)); #elif defined(POSIX_ASYNC_IO) slot->control.aio_lio_opcode = LIO_WRITE; err = (ulint) aio_write(&(slot->control)); printf("Starting Posix aio write %lu\n", err); #endif } else { if (!wake_later) { os_aio_simulated_wake_handler_thread( os_aio_get_segment_no_from_slot(array, slot)); } } } else { ut_error; } #ifdef WIN_ASYNC_IO if (os_aio_use_native_aio) { if ((ret && len == n) || (!ret && GetLastError() == ERROR_IO_PENDING)) { /* aio was queued successfully! */ if (mode == OS_AIO_SYNC) { /* We want a synchronous i/o operation on a file where we also use async i/o: in Windows we must use the same wait mechanism as for async i/o */ return(os_aio_windows_handle(ULINT_UNDEFINED, slot->pos, &dummy_mess1, &dummy_mess2, &dummy_type)); } return(TRUE); } err = 1; /* Fall through the next if */ } #endif if (err == 0) { /* aio was queued successfully! */ return(TRUE); } os_aio_array_free_slot(array, slot); retry = os_file_handle_error(file, name); if (retry) { goto try_again; } ut_error; return(FALSE); } #ifdef WIN_ASYNC_IO /************************************************************************** This function is only used in Windows asynchronous i/o. Waits for an aio operation to complete. This function is used to wait the for completed requests. The aio array of pending requests is divided into segments. The thread specifies which segment or slot it wants to wait for. NOTE: this function will also take care of freeing the aio slot, therefore no other thread is allowed to do the freeing! */ ibool os_aio_windows_handle( /*==================*/ /* out: TRUE if the aio operation succeeded */ ulint segment, /* in: the number of the segment in the aio arrays to wait for; segment 0 is the ibuf i/o thread, segment 1 the log i/o thread, then follow the non-ibuf read threads, and as the last are the non-ibuf write threads; if this is ULINT_UNDEFINED, then it means that sync aio is used, and this parameter is ignored */ ulint pos, /* this parameter is used only in sync aio: wait for the aio slot at this position */ void** message1, /* out: the messages passed with the aio request; note that also in the case where the aio operation failed, these output parameters are valid and can be used to restart the operation, for example */ void** message2, ulint* type) /* out: OS_FILE_WRITE or ..._READ */ { ulint orig_seg = segment; os_aio_array_t* array; os_aio_slot_t* slot; ulint n; ulint i; ibool ret_val; ulint err; BOOL ret; DWORD len; if (segment == ULINT_UNDEFINED) { array = os_aio_sync_array; segment = 0; } else { segment = os_aio_get_array_and_local_segment(&array, segment); } /* NOTE! We only access constant fields in os_aio_array. Therefore we do not have to acquire the protecting mutex yet */ ut_ad(os_aio_validate()); ut_ad(segment < array->n_segments); n = array->n_slots / array->n_segments; if (array == os_aio_sync_array) { srv_io_thread_op_info[orig_seg] = "wait windows aio for 1 page"; ut_ad(pos < array->n_slots); os_event_wait(array->events[pos]); i = pos; } else { srv_io_thread_op_info[orig_seg] = "wait windows aio for n pages"; i = os_event_wait_multiple(n, (array->events) + segment * n); } os_mutex_enter(array->mutex); slot = os_aio_array_get_nth_slot(array, i + segment * n); ut_a(slot->reserved); srv_io_thread_op_info[orig_seg] = "get windows aio return value"; ret = GetOverlappedResult(slot->file, &(slot->control), &len, TRUE); *message1 = slot->message1; *message2 = slot->message2; *type = slot->type; if (ret && len == slot->len) { ret_val = TRUE; if (slot->type == OS_FILE_WRITE && !trx_doublewrite) { ut_a(TRUE == os_file_flush(slot->file)); } } else { err = GetLastError(); ut_error; ret_val = FALSE; } os_mutex_exit(array->mutex); os_aio_array_free_slot(array, slot); return(ret_val); } #endif #ifdef POSIX_ASYNC_IO /************************************************************************** This function is only used in Posix asynchronous i/o. Waits for an aio operation to complete. */ ibool os_aio_posix_handle( /*================*/ /* out: TRUE if the aio operation succeeded */ ulint array_no, /* in: array number 0 - 3 */ void** message1, /* out: the messages passed with the aio request; note that also in the case where the aio operation failed, these output parameters are valid and can be used to restart the operation, for example */ void** message2) { os_aio_array_t* array; os_aio_slot_t* slot; siginfo_t info; sigset_t sigset; sigset_t proc_sigset; sigset_t thr_sigset; int ret; int i; int sig; sigemptyset(&sigset); sigaddset(&sigset, SIGRTMIN + 1 + array_no); pthread_sigmask(SIG_UNBLOCK, &sigset, NULL); /* sigprocmask(0, NULL, &proc_sigset); pthread_sigmask(0, NULL, &thr_sigset); for (i = 32 ; i < 40; i++) { printf("%lu : %lu %lu\n", (ulint)i, (ulint)sigismember(&proc_sigset, i), (ulint)sigismember(&thr_sigset, i)); } */ ret = sigwaitinfo(&sigset, &info); if (sig != SIGRTMIN + 1 + array_no) { ut_a(0); return(FALSE); } printf("Handling Posix aio\n"); array = os_aio_get_array_from_no(array_no); os_mutex_enter(array->mutex); slot = info.si_value.sival_ptr; ut_a(slot->reserved); *message1 = slot->message1; *message2 = slot->message2; if (slot->type == OS_FILE_WRITE && !trx_doublewrite) { ut_a(TRUE == os_file_flush(slot->file)); } os_mutex_exit(array->mutex); os_aio_array_free_slot(array, slot); return(TRUE); } #endif /************************************************************************** Does simulated aio. This function should be called by an i/o-handler thread. */ ibool os_aio_simulated_handle( /*====================*/ /* out: TRUE if the aio operation succeeded */ ulint global_segment, /* in: the number of the segment in the aio arrays to wait for; segment 0 is the ibuf i/o thread, segment 1 the log i/o thread, then follow the non-ibuf read threads, and as the last are the non-ibuf write threads */ void** message1, /* out: the messages passed with the aio request; note that also in the case where the aio operation failed, these output parameters are valid and can be used to restart the operation, for example */ void** message2, ulint* type) /* out: OS_FILE_WRITE or ..._READ */ { os_aio_array_t* array; ulint segment; os_aio_slot_t* slot; os_aio_slot_t* slot2; os_aio_slot_t* consecutive_ios[OS_AIO_MERGE_N_CONSECUTIVE]; ulint n_consecutive; ulint total_len; ulint offs; ulint lowest_offset; byte* combined_buf; ibool ret; ulint n; ulint i; segment = os_aio_get_array_and_local_segment(&array, global_segment); restart: /* Give other threads chance to add several i/os to the array at once */ os_thread_yield(); /* NOTE! We only access constant fields in os_aio_array. Therefore we do not have to acquire the protecting mutex yet */ ut_ad(os_aio_validate()); ut_ad(segment < array->n_segments); n = array->n_slots / array->n_segments; /* Look through n slots after the segment * n'th slot */ os_mutex_enter(array->mutex); /* Check if there is a slot for which the i/o has already been done */ for (i = 0; i < n; i++) { slot = os_aio_array_get_nth_slot(array, i + segment * n); if (slot->reserved && slot->io_already_done) { ret = TRUE; goto slot_io_done; } } n_consecutive = 0; /* Look for an i/o request at the lowest offset in the array */ lowest_offset = ULINT_MAX; for (i = 0; i < n; i++) { slot = os_aio_array_get_nth_slot(array, i + segment * n); if (slot->reserved && slot->offset < lowest_offset) { /* Found an i/o request */ consecutive_ios[0] = slot; n_consecutive = 1; lowest_offset = slot->offset; } } if (n_consecutive == 0) { /* No i/o requested at the moment */ goto wait_for_io; } slot = consecutive_ios[0]; /* Check if there are several consecutive blocks to read or write */ consecutive_loop: for (i = 0; i < n; i++) { slot2 = os_aio_array_get_nth_slot(array, i + segment * n); if (slot2->reserved && slot2 != slot && slot2->offset == slot->offset + slot->len && slot->offset + slot->len > slot->offset /* check that sum does not wrap over */ && slot2->offset_high == slot->offset_high && slot2->type == slot->type && slot2->file == slot->file) { /* Found a consecutive i/o request */ consecutive_ios[n_consecutive] = slot2; n_consecutive++; slot = slot2; if (n_consecutive < OS_AIO_MERGE_N_CONSECUTIVE) { goto consecutive_loop; } else { break; } } } /* We have now collected n_consecutive i/o requests in the array; allocate a single buffer which can hold all data, and perform the i/o */ total_len = 0; slot = consecutive_ios[0]; for (i = 0; i < n_consecutive; i++) { total_len += consecutive_ios[i]->len; } if (n_consecutive == 1) { /* We can use the buffer of the i/o request */ combined_buf = slot->buf; } else { combined_buf = ut_malloc(total_len); ut_a(combined_buf); } /* We release the array mutex for the time of the i/o: NOTE that this assumes that there is just one i/o-handler thread serving a single segment of slots! */ os_mutex_exit(array->mutex); if (slot->type == OS_FILE_WRITE && n_consecutive > 1) { /* Copy the buffers to the combined buffer */ offs = 0; for (i = 0; i < n_consecutive; i++) { ut_memcpy(combined_buf + offs, consecutive_ios[i]->buf, consecutive_ios[i]->len); offs += consecutive_ios[i]->len; } } srv_io_thread_op_info[global_segment] = "doing file i/o"; /* Do the i/o with ordinary, synchronous i/o functions: */ if (slot->type == OS_FILE_WRITE) { ret = os_file_write(slot->name, slot->file, combined_buf, slot->offset, slot->offset_high, total_len); } else { ret = os_file_read(slot->file, combined_buf, slot->offset, slot->offset_high, total_len); } ut_a(ret); srv_io_thread_op_info[global_segment] = "file i/o done"; /* printf("aio: %lu consecutive %lu:th segment, first offs %lu blocks\n", n_consecutive, global_segment, slot->offset / UNIV_PAGE_SIZE); */ if (slot->type == OS_FILE_READ && n_consecutive > 1) { /* Copy the combined buffer to individual buffers */ offs = 0; for (i = 0; i < n_consecutive; i++) { ut_memcpy(consecutive_ios[i]->buf, combined_buf + offs, consecutive_ios[i]->len); offs += consecutive_ios[i]->len; } } if (n_consecutive > 1) { ut_free(combined_buf); } os_mutex_enter(array->mutex); /* Mark the i/os done in slots */ for (i = 0; i < n_consecutive; i++) { consecutive_ios[i]->io_already_done = TRUE; } /* We return the messages for the first slot now, and if there were several slots, the messages will be returned with subsequent calls of this function */ slot_io_done: ut_a(slot->reserved); *message1 = slot->message1; *message2 = slot->message2; *type = slot->type; os_mutex_exit(array->mutex); os_aio_array_free_slot(array, slot); return(ret); wait_for_io: /* We wait here until there again can be i/os in the segment of this thread */ os_event_reset(os_aio_segment_wait_events[global_segment]); os_mutex_exit(array->mutex); srv_io_thread_op_info[global_segment] = "waiting for i/o request"; os_event_wait(os_aio_segment_wait_events[global_segment]); goto restart; } /************************************************************************** Validates the consistency of an aio array. */ static ibool os_aio_array_validate( /*==================*/ /* out: TRUE if ok */ os_aio_array_t* array) /* in: aio wait array */ { os_aio_slot_t* slot; ulint n_reserved = 0; ulint i; ut_a(array); os_mutex_enter(array->mutex); ut_a(array->n_slots > 0); ut_a(array->n_segments > 0); for (i = 0; i < array->n_slots; i++) { slot = os_aio_array_get_nth_slot(array, i); if (slot->reserved) { n_reserved++; ut_a(slot->len > 0); } } ut_a(array->n_reserved == n_reserved); os_mutex_exit(array->mutex); return(TRUE); } /************************************************************************** Validates the consistency the aio system. */ ibool os_aio_validate(void) /*=================*/ /* out: TRUE if ok */ { os_aio_array_validate(os_aio_read_array); os_aio_array_validate(os_aio_write_array); os_aio_array_validate(os_aio_ibuf_array); os_aio_array_validate(os_aio_log_array); os_aio_array_validate(os_aio_sync_array); return(TRUE); } /************************************************************************** Prints info of the aio arrays. */ void os_aio_print(void) /*==============*/ { os_aio_array_t* array; os_aio_slot_t* slot; ulint n_reserved; ulint i; for (i = 0; i < srv_n_file_io_threads; i++) { printf("I/O thread %lu state: %s\n", i, srv_io_thread_op_info[i]); } printf("Pending normal aio reads: "); array = os_aio_read_array; loop: ut_a(array); os_mutex_enter(array->mutex); ut_a(array->n_slots > 0); ut_a(array->n_segments > 0); n_reserved = 0; for (i = 0; i < array->n_slots; i++) { slot = os_aio_array_get_nth_slot(array, i); if (slot->reserved) { n_reserved++; /* printf("Reserved slot, messages %lx %lx\n", (ulint)slot->message1, (ulint)slot->message2); */ ut_a(slot->len > 0); } } ut_a(array->n_reserved == n_reserved); printf("%lu\n", n_reserved); os_mutex_exit(array->mutex); if (array == os_aio_read_array) { printf("Pending aio writes: "); array = os_aio_write_array; goto loop; } if (array == os_aio_write_array) { printf("Pending insert buffer aio reads: "); array = os_aio_ibuf_array; goto loop; } if (array == os_aio_ibuf_array) { printf("Pending log writes or reads: "); array = os_aio_log_array; goto loop; } if (array == os_aio_log_array) { printf("Pending synchronous reads or writes: "); array = os_aio_sync_array; goto loop; } } /************************************************************************** Checks that all slots in the system have been freed, that is, there are no pending io operations. */ ibool os_aio_all_slots_free(void) /*=======================*/ /* out: TRUE if all free */ { os_aio_array_t* array; ulint n_res = 0; array = os_aio_read_array; os_mutex_enter(array->mutex); n_res += array->n_reserved; os_mutex_exit(array->mutex); array = os_aio_write_array; os_mutex_enter(array->mutex); n_res += array->n_reserved; os_mutex_exit(array->mutex); array = os_aio_ibuf_array; os_mutex_enter(array->mutex); n_res += array->n_reserved; os_mutex_exit(array->mutex); array = os_aio_log_array; os_mutex_enter(array->mutex); n_res += array->n_reserved; os_mutex_exit(array->mutex); array = os_aio_sync_array; os_mutex_enter(array->mutex); n_res += array->n_reserved; os_mutex_exit(array->mutex); if (n_res == 0) { return(TRUE); } return(FALSE); }