mariadb/mysys/my_open.c
Davi Arnaut f56dd32bf7 Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled
Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.

Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.

Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost. 

The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.

Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives.

client/mysqldump.c:
  Pass my_free directly as its signature is compatible with the
  callback type -- which wasn't the case for free_table_ent.
2010-07-08 18:20:08 -03:00

192 lines
4.6 KiB
C

/* Copyright (C) 2000 MySQL AB, 2008-2009 Sun Microsystems, Inc
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
#include "mysys_priv.h"
#include "mysys_err.h"
#include <my_dir.h>
#include <errno.h>
/*
Open a file
SYNOPSIS
my_open()
FileName Fully qualified file name
Flags Read | write
MyFlags Special flags
RETURN VALUE
File descriptor
*/
File my_open(const char *FileName, int Flags, myf MyFlags)
/* Path-name of file */
/* Read | write .. */
/* Special flags */
{
File fd;
DBUG_ENTER("my_open");
DBUG_PRINT("my",("Name: '%s' Flags: %d MyFlags: %d",
FileName, Flags, MyFlags));
#if defined(_WIN32)
fd= my_win_open(FileName, Flags);
#elif !defined(NO_OPEN_3)
fd = open(FileName, Flags, my_umask); /* Normal unix */
#else
fd = open((char *) FileName, Flags);
#endif
DBUG_RETURN(my_register_filename(fd, FileName, FILE_BY_OPEN,
EE_FILENOTFOUND, MyFlags));
} /* my_open */
/*
Close a file
SYNOPSIS
my_close()
fd File sescriptor
myf Special Flags
*/
int my_close(File fd, myf MyFlags)
{
int err;
DBUG_ENTER("my_close");
DBUG_PRINT("my",("fd: %d MyFlags: %d",fd, MyFlags));
mysql_mutex_lock(&THR_LOCK_open);
#ifndef _WIN32
do
{
err= close(fd);
} while (err == -1 && errno == EINTR);
#else
err= my_win_close(fd);
#endif
if (err)
{
DBUG_PRINT("error",("Got error %d on close",err));
my_errno=errno;
if (MyFlags & (MY_FAE | MY_WME))
my_error(EE_BADCLOSE, MYF(ME_BELL+ME_WAITTANG),my_filename(fd),errno);
}
if ((uint) fd < my_file_limit && my_file_info[fd].type != UNOPEN)
{
my_free(my_file_info[fd].name);
#if defined(THREAD) && !defined(HAVE_PREAD) && !defined(_WIN32)
mysql_mutex_destroy(&my_file_info[fd].mutex);
#endif
my_file_info[fd].type = UNOPEN;
}
my_file_opened--;
mysql_mutex_unlock(&THR_LOCK_open);
DBUG_RETURN(err);
} /* my_close */
/*
Register file in my_file_info[]
SYNOPSIS
my_register_filename()
fd File number opened, -1 if error on open
FileName File name
type_file_type How file was created
error_message_number Error message number if caller got error (fd == -1)
MyFlags Flags for my_close()
RETURN
-1 error
# Filenumber
*/
File my_register_filename(File fd, const char *FileName, enum file_type
type_of_file, uint error_message_number, myf MyFlags)
{
DBUG_ENTER("my_register_filename");
if ((int) fd >= MY_FILE_MIN)
{
if ((uint) fd >= my_file_limit)
{
#if defined(THREAD) && !defined(HAVE_PREAD)
my_errno= EMFILE;
#else
thread_safe_increment(my_file_opened,&THR_LOCK_open);
DBUG_RETURN(fd); /* safeguard */
#endif
}
else
{
mysql_mutex_lock(&THR_LOCK_open);
if ((my_file_info[fd].name = (char*) my_strdup(FileName,MyFlags)))
{
my_file_opened++;
my_file_total_opened++;
my_file_info[fd].type = type_of_file;
#if defined(THREAD) && !defined(HAVE_PREAD) && !defined(_WIN32)
mysql_mutex_init(key_my_file_info_mutex, &my_file_info[fd].mutex,
MY_MUTEX_INIT_FAST);
#endif
mysql_mutex_unlock(&THR_LOCK_open);
DBUG_PRINT("exit",("fd: %d",fd));
DBUG_RETURN(fd);
}
mysql_mutex_unlock(&THR_LOCK_open);
my_errno= ENOMEM;
}
(void) my_close(fd, MyFlags);
}
else
my_errno= errno;
DBUG_PRINT("error",("Got error %d on open", my_errno));
if (MyFlags & (MY_FFNF | MY_FAE | MY_WME))
{
if (my_errno == EMFILE)
error_message_number= EE_OUT_OF_FILERESOURCES;
DBUG_PRINT("error",("print err: %d",error_message_number));
my_error(error_message_number, MYF(ME_BELL+ME_WAITTANG),
FileName, my_errno);
}
DBUG_RETURN(-1);
}
#ifdef EXTRA_DEBUG
void my_print_open_files(void)
{
if (my_file_opened | my_stream_opened)
{
uint i;
for (i= 0 ; i < my_file_limit ; i++)
{
if (my_file_info[i].type != UNOPEN)
{
fprintf(stderr, EE(EE_FILE_NOT_CLOSED), my_file_info[i].name, i);
fputc('\n', stderr);
}
}
}
}
#endif