1 /* Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
2
3 This program is free software; you can redistribute it and/or modify
4 it under the terms of the GNU General Public License as published by
5 the Free Software Foundation; version 2 of the License.
6
7 This program is distributed in the hope that it will be useful,
8 but WITHOUT ANY WARRANTY; without even the implied warranty of
9 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
10 GNU General Public License for more details.
11
12 You should have received a copy of the GNU General Public License
13 along with this program; if not, write to the Free Software
14 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
15
16 #include "mysys_priv.h"
17 #include "mysys_err.h"
18 #include <errno.h>
19 #undef MY_HOW_OFTEN_TO_ALARM
20 #define MY_HOW_OFTEN_TO_ALARM ((int) my_time_to_wait_for_lock)
21 #ifdef NO_ALARM_LOOP
22 #undef NO_ALARM_LOOP
23 #endif
24 #include <my_alarm.h>
25
26 #ifdef _WIN32
27 #define WIN_LOCK_INFINITE -1
28 #define WIN_LOCK_SLEEP_MILLIS 100
29
win_lock(File fd,int locktype,my_off_t start,my_off_t length,int timeout_sec)30 static int win_lock(File fd, int locktype, my_off_t start, my_off_t length,
31 int timeout_sec)
32 {
33 LARGE_INTEGER liOffset,liLength;
34 DWORD dwFlags;
35 OVERLAPPED ov= {0};
36 HANDLE hFile= (HANDLE)my_get_osfhandle(fd);
37 int i;
38 int timeout_millis= timeout_sec * 1000;
39
40 DBUG_ENTER("win_lock");
41
42 liOffset.QuadPart= start;
43 liLength.QuadPart= length;
44
45 ov.Offset= liOffset.LowPart;
46 ov.OffsetHigh= liOffset.HighPart;
47
48 if (locktype == F_UNLCK)
49 {
50 if (UnlockFileEx(hFile, 0, liLength.LowPart, liLength.HighPart, &ov))
51 DBUG_RETURN(0);
52 /*
53 For compatibility with fcntl implementation, ignore error,
54 if region was not locked
55 */
56 if (GetLastError() == ERROR_NOT_LOCKED)
57 {
58 SetLastError(0);
59 DBUG_RETURN(0);
60 }
61 goto error;
62 }
63 else if (locktype == F_RDLCK)
64 /* read lock is mapped to a shared lock. */
65 dwFlags= 0;
66 else
67 /* write lock is mapped to an exclusive lock. */
68 dwFlags= LOCKFILE_EXCLUSIVE_LOCK;
69
70 /*
71 Drop old lock first to avoid double locking.
72 During analyze of Bug#38133 (Myisamlog test fails on Windows)
73 I met the situation that the program myisamlog locked the file
74 exclusively, then additionally shared, then did one unlock, and
75 then blocked on an attempt to lock it exclusively again.
76 Unlocking before every lock fixed the problem.
77 Note that this introduces a race condition. When the application
78 wants to convert an exclusive lock into a shared one, it will now
79 first unlock the file and then lock it shared. A waiting exclusive
80 lock could step in here. For reasons described in Bug#38133 and
81 Bug#41124 (Server hangs on Windows with --external-locking after
82 INSERT...SELECT) and in the review thread at
83 http://lists.mysql.com/commits/60721 it seems to be the better
84 option than not to unlock here.
85 If one day someone notices a way how to do file lock type changes
86 on Windows without unlocking before taking the new lock, please
87 change this code accordingly to fix the race condition.
88 */
89 if (!UnlockFileEx(hFile, 0, liLength.LowPart, liLength.HighPart, &ov) &&
90 (GetLastError() != ERROR_NOT_LOCKED))
91 goto error;
92
93 if (timeout_sec == WIN_LOCK_INFINITE)
94 {
95 if (LockFileEx(hFile, dwFlags, 0, liLength.LowPart, liLength.HighPart, &ov))
96 DBUG_RETURN(0);
97 goto error;
98 }
99
100 dwFlags|= LOCKFILE_FAIL_IMMEDIATELY;
101 timeout_millis= timeout_sec * 1000;
102 /* Try lock in a loop, until the lock is acquired or timeout happens */
103 for(i= 0; ;i+= WIN_LOCK_SLEEP_MILLIS)
104 {
105 if (LockFileEx(hFile, dwFlags, 0, liLength.LowPart, liLength.HighPart, &ov))
106 DBUG_RETURN(0);
107
108 if (GetLastError() != ERROR_LOCK_VIOLATION)
109 goto error;
110
111 if (i >= timeout_millis)
112 break;
113 Sleep(WIN_LOCK_SLEEP_MILLIS);
114 }
115
116 /* timeout */
117 errno= EAGAIN;
118 DBUG_RETURN(-1);
119
120 error:
121 my_osmaperr(GetLastError());
122 DBUG_RETURN(-1);
123 }
124 #endif
125
126
127
128 /*
129 Lock a part of a file
130
131 RETURN VALUE
132 0 Success
133 -1 An error has occurred and 'my_errno' is set
134 to indicate the actual error code.
135 */
136
my_lock(File fd,int locktype,my_off_t start,my_off_t length,myf MyFlags)137 int my_lock(File fd, int locktype, my_off_t start, my_off_t length,
138 myf MyFlags)
139 {
140 #ifdef HAVE_FCNTL
141 int value;
142 ALARM_VARIABLES;
143 #endif
144
145 DBUG_ENTER("my_lock");
146 DBUG_PRINT("my",("fd: %d Op: %d start: %ld Length: %ld MyFlags: %lu",
147 fd,locktype,(long) start,(long) length,MyFlags));
148 if (my_disable_locking && ! (MyFlags & MY_FORCE_LOCK))
149 DBUG_RETURN(0);
150
151 #if defined(_WIN32)
152 {
153 int timeout_sec;
154 if (MyFlags & MY_NO_WAIT)
155 timeout_sec= 0;
156 else
157 timeout_sec= WIN_LOCK_INFINITE;
158
159 if (win_lock(fd, locktype, start, length, timeout_sec) == 0)
160 DBUG_RETURN(0);
161 }
162 #else
163 #if defined(HAVE_FCNTL)
164 {
165 struct flock lock;
166
167 lock.l_type= (short) locktype;
168 lock.l_whence= SEEK_SET;
169 lock.l_start= (off_t) start;
170 lock.l_len= (off_t) length;
171
172 if (MyFlags & (MY_NO_WAIT | MY_SHORT_WAIT))
173 {
174 if (fcntl(fd,F_SETLK,&lock) != -1) /* Check if we can lock */
175 DBUG_RETURN(0); /* Ok, file locked */
176 if (MyFlags & MY_NO_WAIT)
177 {
178 my_errno= (errno == EACCES) ? EAGAIN : errno ? errno : -1;
179 DBUG_RETURN(-1);
180 }
181
182 DBUG_PRINT("info",("Was locked, trying with alarm"));
183 ALARM_INIT;
184 while ((value=fcntl(fd,F_SETLKW,&lock)) && ! ALARM_TEST &&
185 errno == EINTR)
186 { /* Setup again so we don`t miss it */
187 ALARM_REINIT;
188 }
189 ALARM_END;
190 if (value != -1)
191 DBUG_RETURN(0);
192 if (errno == EINTR)
193 errno=EAGAIN;
194 }
195 else if (fcntl(fd,F_SETLKW,&lock) != -1) /* Wait until a lock */
196 DBUG_RETURN(0);
197 }
198 #else
199 if (MyFlags & MY_SEEK_NOT_DONE)
200 {
201 if (my_seek(fd,start,MY_SEEK_SET,MYF(MyFlags & ~MY_SEEK_NOT_DONE))
202 == MY_FILEPOS_ERROR)
203 {
204 /*
205 If an error has occurred in my_seek then we will already
206 have an error code in my_errno; Just return error code.
207 */
208 DBUG_RETURN(-1);
209 }
210 }
211 if (lockf(fd,locktype,length) != -1)
212 DBUG_RETURN(0);
213 #endif /* HAVE_FCNTL */
214 #endif /* _WIN32 */
215
216 /* We got an error. We don't want EACCES errors */
217 my_errno=(errno == EACCES) ? EAGAIN : errno ? errno : -1;
218
219 if (MyFlags & MY_WME)
220 {
221 if (locktype == F_UNLCK)
222 my_error(EE_CANTUNLOCK,MYF(ME_BELL+ME_WAITTANG),my_errno);
223 else
224 my_error(EE_CANTLOCK,MYF(ME_BELL+ME_WAITTANG),my_errno);
225 }
226 DBUG_PRINT("error",("my_errno: %d (%d)",my_errno,errno));
227 DBUG_RETURN(-1);
228 } /* my_lock */
229