Merge mysql.com:/home/svoj/devel/mysql/BUG25712/mysql-4.1-engines

into  mysql.com:/home/svoj/devel/mysql/BUG25712/mysql-5.0-engines

1 files changed, 13 insertions, 4 deletions

diff --git a/mysys/my_seek.c b/mysys/my_seek.c
index 2be4812a2bd..d46a02a6a50 100644
--- a/mysys/my_seek.c
+++ b/mysys/my_seek.c
@@ -23,7 +23,9 @@
   my_off_t pos     The expected position (absolute or relative)
   int whence       A direction parameter and one of 
                    {SEEK_SET, SEEK_CUR, SEEK_END}
-  myf MyFlags      Not used.
+  myf MyFlags      MY_THREADSAFE must be set in case my_seek may be mixed
+                   with my_pread/my_pwrite calls and fd is shared among
+                   threads.
 
   DESCRIPTION
     The my_seek  function  is a wrapper around the system call lseek and
@@ -54,9 +56,16 @@ my_off_t my_seek(File fd, my_off_t pos, int whence,
       Make sure we are using a valid file descriptor!
   */
   DBUG_ASSERT(fd != -1);
-
-  newpos= lseek(fd, pos, whence);
-  
+#if defined(THREAD) && !defined(HAVE_PREAD)
+  if (MyFlags & MY_THREADSAFE)
+  {
+    pthread_mutex_lock(&my_file_info[fd].mutex);
+    newpos= lseek(fd, pos, whence);
+    pthread_mutex_lock(&my_file_info[fd].mutex);
+  }
+  else
+#endif
+    newpos= lseek(fd, pos, whence);
   if (newpos == (os_off_t) -1)
   {
     my_errno=errno;