223 lines
6.9 KiB
C++
223 lines
6.9 KiB
C++
/* Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License, version 2.0,
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as published by the Free Software Foundation.
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This program is also distributed with certain software (including
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but not limited to OpenSSL) that is licensed under separate terms,
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as designated in a particular file or component or in included license
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documentation. The authors of MySQL hereby grant you an additional
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permission to link the program and your derivative works with the
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separately licensed software that they have included with MySQL.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License, version 2.0, for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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#include "my_config.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <sys/types.h>
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#ifdef HAVE_UNISTD_H
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#include <unistd.h>
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#endif
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#include "my_compiler.h"
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#include "my_dbug.h"
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#include "my_inttypes.h"
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#include "my_io.h"
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#include "my_sys.h"
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#include "my_thread_local.h"
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#include "mysys_err.h"
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#include "storage/myisam/myisam_sys.h"
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#ifndef _WIN32
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#include <signal.h>
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extern "C" {
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typedef void (*sig_return)(int); /* Returns type from signal */
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static int volatile my_have_got_alarm = 0;
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static uint my_time_to_wait_for_lock = 2; /* In seconds */
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static void my_set_alarm_variable(int signo MY_ATTRIBUTE((unused))) {
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my_have_got_alarm = 1; /* Tell program that time expired */
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}
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} // extern C
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#endif /* !_WIN32 */
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#ifdef _WIN32
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#define WIN_LOCK_INFINITE -1
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#define WIN_LOCK_SLEEP_MILLIS 100
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static int win_lock(File fd, int locktype, my_off_t start, my_off_t length,
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int timeout_sec) {
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LARGE_INTEGER liOffset, liLength;
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DWORD dwFlags;
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OVERLAPPED ov = {0};
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HANDLE hFile = (HANDLE)my_get_osfhandle(fd);
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DWORD lastError = 0;
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int i;
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int timeout_millis = timeout_sec * 1000;
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DBUG_TRACE;
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liOffset.QuadPart = start;
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liLength.QuadPart = length;
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ov.Offset = liOffset.LowPart;
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ov.OffsetHigh = liOffset.HighPart;
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if (locktype == F_UNLCK) {
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if (UnlockFileEx(hFile, 0, liLength.LowPart, liLength.HighPart, &ov))
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return 0;
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/*
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For compatibility with fcntl implementation, ignore error,
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if region was not locked
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*/
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if (GetLastError() == ERROR_NOT_LOCKED) {
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SetLastError(0);
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return 0;
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}
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goto error;
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} else if (locktype == F_RDLCK)
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/* read lock is mapped to a shared lock. */
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dwFlags = 0;
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else
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/* write lock is mapped to an exclusive lock. */
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dwFlags = LOCKFILE_EXCLUSIVE_LOCK;
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/*
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Drop old lock first to avoid double locking.
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During analyze of Bug#38133 (Myisamlog test fails on Windows)
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I met the situation that the program myisamlog locked the file
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exclusively, then additionally shared, then did one unlock, and
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then blocked on an attempt to lock it exclusively again.
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Unlocking before every lock fixed the problem.
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Note that this introduces a race condition. When the application
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wants to convert an exclusive lock into a shared one, it will now
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first unlock the file and then lock it shared. A waiting exclusive
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lock could step in here. For reasons described in Bug#38133 and
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Bug#41124 (Server hangs on Windows with --external-locking after
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INSERT...SELECT) and in the review thread at
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http://lists.mysql.com/commits/60721 it seems to be the better
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option than not to unlock here.
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If one day someone notices a way how to do file lock type changes
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on Windows without unlocking before taking the new lock, please
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change this code accordingly to fix the race condition.
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*/
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if (!UnlockFileEx(hFile, 0, liLength.LowPart, liLength.HighPart, &ov) &&
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(GetLastError() != ERROR_NOT_LOCKED))
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goto error;
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if (timeout_sec == WIN_LOCK_INFINITE) {
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if (LockFileEx(hFile, dwFlags, 0, liLength.LowPart, liLength.HighPart, &ov))
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return 0;
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goto error;
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}
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dwFlags |= LOCKFILE_FAIL_IMMEDIATELY;
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timeout_millis = timeout_sec * 1000;
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/* Try lock in a loop, until the lock is acquired or timeout happens */
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for (i = 0;; i += WIN_LOCK_SLEEP_MILLIS) {
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if (LockFileEx(hFile, dwFlags, 0, liLength.LowPart, liLength.HighPart, &ov))
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return 0;
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if (GetLastError() != ERROR_LOCK_VIOLATION) goto error;
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if (i >= timeout_millis) break;
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Sleep(WIN_LOCK_SLEEP_MILLIS);
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}
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/* timeout */
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errno = EAGAIN;
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return -1;
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error:
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my_osmaperr(GetLastError());
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return -1;
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}
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#endif
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/*
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Lock a part of a file
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RETURN VALUE
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0 Success
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-1 An error has occurred and 'my_errno' is set
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to indicate the actual error code.
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*/
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int my_lock(File fd, int locktype, myf MyFlags) {
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DBUG_TRACE;
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DBUG_PRINT("my", ("fd: %d Op: %d MyFlags: %d", fd, locktype, MyFlags));
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if (my_disable_locking) return 0;
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#if defined(_WIN32)
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{
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int timeout_sec;
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if (MyFlags & MY_DONT_WAIT)
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timeout_sec = 0;
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else
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timeout_sec = WIN_LOCK_INFINITE;
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if (win_lock(fd, locktype, 0, 0x3FFFFFFF, timeout_sec) == 0) return 0;
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}
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#else
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{
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struct flock lock;
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lock.l_type = (short)locktype;
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lock.l_whence = SEEK_SET;
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lock.l_start = 0;
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lock.l_len = 0; // End of file.
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if (MyFlags & MY_DONT_WAIT) {
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int value;
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uint alarm_old;
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sig_return alarm_signal;
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if (fcntl(fd, F_SETLK, &lock) != -1) /* Check if we can lock */
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return 0; /* Ok, file locked */
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DBUG_PRINT("info", ("Was locked, trying with alarm"));
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my_have_got_alarm = 0;
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alarm_old = alarm(my_time_to_wait_for_lock);
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alarm_signal = signal(SIGALRM, my_set_alarm_variable);
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while ((value = fcntl(fd, F_SETLKW, &lock)) && !my_have_got_alarm &&
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errno == EINTR) { /* Setup again so we don`t miss it */
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(void)alarm(my_time_to_wait_for_lock);
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my_have_got_alarm = 0;
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}
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(void)signal(SIGALRM, alarm_signal);
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(void)alarm(alarm_old);
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if (value != -1) return 0;
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if (errno == EINTR) errno = EAGAIN;
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} else if (fcntl(fd, F_SETLKW, &lock) != -1) /* Wait until a lock */
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return 0;
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}
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#endif /* _WIN32 */
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/* We got an error. We don't want EACCES errors */
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set_my_errno((errno == EACCES) ? EAGAIN : errno ? errno : -1);
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if (MyFlags & MY_WME) {
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char errbuf[MYSYS_STRERROR_SIZE];
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if (locktype == F_UNLCK)
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my_error(EE_CANTUNLOCK, MYF(0), my_errno(),
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my_strerror(errbuf, sizeof(errbuf), my_errno()));
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else
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my_error(EE_CANTLOCK, MYF(0), my_errno(),
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my_strerror(errbuf, sizeof(errbuf), my_errno()));
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}
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DBUG_PRINT("error", ("my_errno: %d (%d)", my_errno(), errno));
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return -1;
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} /* my_lock */
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