Backport into build-201102032246-5.1.52sp1

> ------------------------------------------------------------
> revno: 3536
> revision-id: davi.arnaut@oracle.com-20110107183336-kp8niwm2hz3wb4c3
> parent: saikumar.v@sun.com-20110106103945-rhsek9uy6f63db44
> committer: Davi Arnaut <davi.arnaut@oracle.com>
> branch nick: 51023-5.1
> timestamp: Fri 2011-01-07 16:33:36 -0200
> message:
>   Bug#51023: Mysql server crashes on SIGHUP and destroys InnoDB files
>   
>   From a user perspective, the problem is that a FLUSH LOGS or SIGHUP
>   signal could end up associating the stdout and stderr to random
>   files. In the case of this bug report, the streams would end up
>   associated to InnoDB ibd files.
>   
>   The freopen(3) function is not thread-safe on FreeBSD. What this
>   means is that if another thread calls open(2) during freopen()
>   is executing that another thread's fd returned by open(2) may get
>   re-associated with the file being passed to freopen(3). See FreeBSD
>   PR number 79887 for reference:
>   
>     http://www.freebsd.org/cgi/query-pr.cgi?pr=79887
>   
>   This problem is worked around by substituting a internal hook within
>   the FILE structure. This avoids the loss of atomicity by not having
>   the original fd closed before its duplicated.
>   
>   Patch based on the original work by Vasil Dimov.

include/my_sys.h

@@ -664,6 +664,7 @@ extern void init_glob_errs(void);
 extern void wait_for_free_space(const char *filename, int errors);
 extern FILE *my_fopen(const char *FileName,int Flags,myf MyFlags);
 extern FILE *my_fdopen(File Filedes,const char *name, int Flags,myf MyFlags);
+extern FILE *my_freopen(const char *path, const char *mode, FILE *stream);
 extern int my_fclose(FILE *fd,myf MyFlags);
 extern int my_chsize(File fd,my_off_t newlength, int filler, myf MyFlags);
 extern int my_sync(File fd, myf my_flags);

mysys/my_fopen.c

@@ -18,6 +18,10 @@
 #include <errno.h>
 #include "mysys_err.h"
 
+#if defined(__FreeBSD__)
+extern int getosreldate(void);
+#endif
+
 static void make_ftype(char * to,int flag);
 
 /*
@@ -97,8 +101,137 @@ FILE *my_fopen(const char *filename, int flags, myf MyFlags)
 } /* my_fopen */
 
 
-	/* Close a stream */
+#if defined(_WIN32)
+
+static FILE *my_win_freopen(const char *path, FILE *stream)
+{
+  int handle_fd, fd= _fileno(stream);
+  HANDLE osfh;
+
+  DBUG_ASSERT(filename && stream);
+
+  /* Services don't have stdout/stderr on Windows, so _fileno returns -1. */
+  if (fd < 0)
+  {
+    if (!freopen(filename, mode, stream))
+      return NULL;
+
+    fd= _fileno(stream);
+  }
+
+  if ((osfh= CreateFile(path, GENERIC_READ | GENERIC_WRITE,
+                        FILE_SHARE_READ | FILE_SHARE_WRITE |
+                        FILE_SHARE_DELETE, NULL,
+                        OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL,
+                        NULL)) == INVALID_HANDLE_VALUE)
+    return NULL;
+
+  if ((handle_fd= _open_osfhandle((intptr_t)osfh,
+                                  _O_APPEND | _O_TEXT)) == -1)
+  {
+    CloseHandle(osfh);
+    return NULL;
+  }
+
+  if (_dup2(handle_fd, fd) < 0)
+  {
+    CloseHandle(osfh);
+    return NULL;
+  }
+
+  _close(handle_fd);
+
+  return stream;
+}
+
+#elif defined(__FreeBSD__)
+
+/* No close operation hook. */
+
+static int no_close(void *cookie __attribute__((unused)))
+{
+  return 0;
+}
+
+/*
+  A hack around a race condition in the implementation of freopen.
+
+  The race condition steams from the fact that the current fd of
+  the stream is closed before its number is used to duplicate the
+  new file descriptor. This defeats the desired atomicity of the
+  close and duplicate of dup2().
+
+  See PR number 79887 for reference:
+  http://www.freebsd.org/cgi/query-pr.cgi?pr=79887
+*/
+
+static FILE *my_freebsd_freopen(const char *path, const char *mode, FILE *stream)
+{
+  int old_fd;
+  FILE *result;
+
+  flockfile(stream);
+
+  old_fd= fileno(stream);
+
+  /* Use a no operation close hook to avoid having the fd closed. */
+  stream->_close= no_close;
+
+  /* Relies on the implicit dup2 to close old_fd. */
+  result= freopen(path, mode, stream);
+
+  /* If successful, the _close hook was replaced. */
+
+  if (result == NULL)
+    close(old_fd);
+  else
+    funlockfile(result);
+
+  return result;
+}
+
+#endif
+
+
+/**
+  Change the file associated with a file stream.
+
+  @param path   Path to file.
+  @param mode   Mode of the stream.
+  @param stream File stream.
+
+  @note
+    This function is used to redirect stdout and stderr to a file and
+    subsequently to close and reopen that file for log rotation.
+
+  @retval A FILE pointer on success. Otherwise, NULL.
+*/
+
+FILE *my_freopen(const char *path, const char *mode, FILE *stream)
+{
+  FILE *result;
+
+#if defined(_WIN32)
+  result= my_win_freopen(path, mode, stream);
+#elif defined(__FreeBSD__)
+  /*
+    XXX: Once the fix is ported to the stable releases, this should
+         be dependent upon the specific FreeBSD versions. Check at:
+         http://www.freebsd.org/cgi/query-pr.cgi?pr=79887
+  */
+  if (getosreldate() > 900027)
+    result= freopen(path, mode, stream);
+  else
+    result= my_freebsd_freopen(path, mode, stream);
+#else
+  result= freopen(path, mode, stream);
+#endif
+
+  return result;
+}
+
 
+/* Close a stream */
 int my_fclose(FILE *fd, myf MyFlags)
 {
   int err,file;

sql/log.cc

@@ -5067,80 +5067,26 @@ void sql_perror(const char *message)
 }
 
 
-#ifdef __WIN__
+/*
+  Change the file associated with two output streams. Used to
+  redirect stdout and stderr to a file. The streams are reopened
+  only for appending (writing at end of file).
+*/
 extern "C" my_bool reopen_fstreams(const char *filename,
                                    FILE *outstream, FILE *errstream)
 {
-  int handle_fd;
-  int err_fd, out_fd;
-  HANDLE osfh;
-
-  DBUG_ASSERT(filename && errstream);
-
-  // Services don't have stdout/stderr on Windows, so _fileno returns -1.
-  err_fd= _fileno(errstream);
-  if (err_fd < 0)
-  {
-    if (!freopen(filename, "a+", errstream))
+  if (outstream && !my_freopen(filename, "a", outstream))
     return TRUE;
 
-    setbuf(errstream, NULL);
-    err_fd= _fileno(errstream);
-  }
-
-  if (outstream)
-  {
-    out_fd= _fileno(outstream);
-    if (out_fd < 0)
-    {
-      if (!freopen(filename, "a+", outstream))
+  if (errstream && !my_freopen(filename, "a", errstream))
     return TRUE;
-      out_fd= _fileno(outstream);
-    }
-  }
 
-  if ((osfh= CreateFile(filename, GENERIC_READ | GENERIC_WRITE,
-                        FILE_SHARE_READ | FILE_SHARE_WRITE |
-                        FILE_SHARE_DELETE, NULL,
-                        OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL,
-                        NULL)) == INVALID_HANDLE_VALUE)
-    return TRUE;
-
-  if ((handle_fd= _open_osfhandle((intptr_t)osfh,
-                                  _O_APPEND | _O_TEXT)) == -1)
-  {
-    CloseHandle(osfh);
-    return TRUE;
-  }
-
-  if (_dup2(handle_fd, err_fd) < 0)
-  {
-    CloseHandle(osfh);
-    return TRUE;
-  }
-
-  if (outstream && _dup2(handle_fd, out_fd) < 0)
-  {
-    CloseHandle(osfh);
-    return TRUE;
-  }
-
-  _close(handle_fd);
-  return FALSE;
-}
-#else
-extern "C" my_bool reopen_fstreams(const char *filename,
-                                   FILE *outstream, FILE *errstream)
-{
-  if (outstream && !freopen(filename, "a+", outstream))
-    return TRUE;
-
-  if (errstream && !freopen(filename, "a+", errstream))
-    return TRUE;
+  /* The error stream must be unbuffered. */
+  if (errstream)
+    setbuf(errstream, NULL);
 
   return FALSE;
 }
-#endif
 
 
 /*