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glibc/libio/libio.h
Szabolcs Nagy d2e0491883 Single threaded stdio optimization 
Locking overhead can be significant in some stdio operations
that are common in single threaded applications.

This patch adds the _IO_FLAGS2_NEED_LOCK flag to indicate if
an _IO_FILE object needs to be locked and some of the stdio
functions just jump to their _unlocked variant when not.  The
flag is set on all _IO_FILE objects when the first thread is
created.  A new GLIBC_PRIVATE libc symbol, _IO_enable_locks,
was added to do this from libpthread.

The optimization can be applied to more stdio functions,
currently it is only applied to single flag check or single
non-wide-char standard operations.  The flag should probably
be never set for files with _IO_USER_LOCK, but that's just a
further optimization, not a correctness requirement.

The optimization is valid in a single thread because stdio
operations are non-as-safe (so lock state is not observable
from a signal handler) and stdio locks are recursive (so lock
state is not observable via deadlock).  The optimization is not
valid if a thread may be created while an stdio lock is taken
and thus it should be disabled if any user code may run during
an stdio operation (interposed malloc, printf hooks, etc).
This makes the optimization more complicated for some stdio
operations (e.g. printf), but those are bigger and thus less
important to optimize so this patch does not try to do that.

	* libio/libio.h (_IO_FLAGS2_NEED_LOCK, _IO_need_lock): Define.
	* libio/libioP.h (_IO_enable_locks): Declare.
	* libio/Versions (_IO_enable_locks): New symbol.
	* libio/genops.c (_IO_enable_locks): Define.
	(_IO_old_init): Initialize flags2.
	* libio/feof.c.c (_IO_feof): Avoid locking when not needed.
	* libio/ferror.c (_IO_ferror): Likewise.
	* libio/fputc.c (fputc): Likewise.
	* libio/putc.c (_IO_putc): Likewise.
	* libio/getc.c (_IO_getc): Likewise.
	* libio/getchar.c (getchar): Likewise.
	* libio/ioungetc.c (_IO_ungetc): Likewise.
	* nptl/pthread_create.c (__pthread_create_2_1): Enable stdio locks.
	* libio/iofopncook.c (_IO_fopencookie): Enable locking for the file.
	* sysdeps/pthread/flockfile.c (__flockfile): Likewise.
2017-07-04 16:05:12 +01:00

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/* Copyright (C) 1991-2017 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Written by Per Bothner <bothner@cygnus.com>.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>.
As a special exception, if you link the code in this file with
files compiled with a GNU compiler to produce an executable,
that does not cause the resulting executable to be covered by
the GNU Lesser General Public License. This exception does not
however invalidate any other reasons why the executable file
might be covered by the GNU Lesser General Public License.
This exception applies to code released by its copyright holders
in files containing the exception. */
#ifndef _IO_STDIO_H
#define _IO_STDIO_H
#include <_G_config.h>
/* ALL of these should be defined in _G_config.h */
#define _IO_fpos_t _G_fpos_t
#define _IO_fpos64_t _G_fpos64_t
#define _IO_size_t size_t
#define _IO_ssize_t __ssize_t
#define _IO_off_t __off_t
#define _IO_off64_t __off64_t
#define _IO_pid_t __pid_t
#define _IO_uid_t __uid_t
#define _IO_iconv_t _G_iconv_t
#define _IO_HAVE_ST_BLKSIZE _G_HAVE_ST_BLKSIZE
#define _IO_BUFSIZ _G_BUFSIZ
#define _IO_va_list _G_va_list
#define _IO_wint_t wint_t
/* This define avoids name pollution if we're using GNU stdarg.h */
#define __need___va_list
#include <stdarg.h>
#ifdef __GNUC_VA_LIST
# undef _IO_va_list
# define _IO_va_list __gnuc_va_list
#endif /* __GNUC_VA_LIST */
#ifndef __P
# include <sys/cdefs.h>
#endif /*!__P*/
#define _IO_UNIFIED_JUMPTABLES 1
#ifndef EOF
# define EOF (-1)
#endif
#ifndef NULL
# if defined __GNUG__ && \
(__GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 8))
# define NULL (__null)
# else
# if !defined(__cplusplus)
# define NULL ((void*)0)
# else
# define NULL (0)
# endif
# endif
#endif
#define _IOS_INPUT 1
#define _IOS_OUTPUT 2
#define _IOS_ATEND 4
#define _IOS_APPEND 8
#define _IOS_TRUNC 16
#define _IOS_NOCREATE 32
#define _IOS_NOREPLACE 64
#define _IOS_BIN 128
/* Magic numbers and bits for the _flags field.
The magic numbers use the high-order bits of _flags;
the remaining bits are available for variable flags.
Note: The magic numbers must all be negative if stdio
emulation is desired. */
#define _IO_MAGIC 0xFBAD0000 /* Magic number */
#define _OLD_STDIO_MAGIC 0xFABC0000 /* Emulate old stdio. */
#define _IO_MAGIC_MASK 0xFFFF0000
#define _IO_USER_BUF 1 /* User owns buffer; don't delete it on close. */
#define _IO_UNBUFFERED 2
#define _IO_NO_READS 4 /* Reading not allowed */
#define _IO_NO_WRITES 8 /* Writing not allowd */
#define _IO_EOF_SEEN 0x10
#define _IO_ERR_SEEN 0x20
#define _IO_DELETE_DONT_CLOSE 0x40 /* Don't call close(_fileno) on cleanup. */
#define _IO_LINKED 0x80 /* Set if linked (using _chain) to streambuf::_list_all.*/
#define _IO_IN_BACKUP 0x100
#define _IO_LINE_BUF 0x200
#define _IO_TIED_PUT_GET 0x400 /* Set if put and get pointer logicly tied. */
#define _IO_CURRENTLY_PUTTING 0x800
#define _IO_IS_APPENDING 0x1000
#define _IO_IS_FILEBUF 0x2000
#define _IO_BAD_SEEN 0x4000
#define _IO_USER_LOCK 0x8000
#define _IO_FLAGS2_MMAP 1
#define _IO_FLAGS2_NOTCANCEL 2
#ifdef _LIBC
# define _IO_FLAGS2_FORTIFY 4
#endif
#define _IO_FLAGS2_USER_WBUF 8
#ifdef _LIBC
# define _IO_FLAGS2_SCANF_STD 16
# define _IO_FLAGS2_NOCLOSE 32
# define _IO_FLAGS2_CLOEXEC 64
# define _IO_FLAGS2_NEED_LOCK 128
#endif
/* These are "formatting flags" matching the iostream fmtflags enum values. */
#define _IO_SKIPWS 01
#define _IO_LEFT 02
#define _IO_RIGHT 04
#define _IO_INTERNAL 010
#define _IO_DEC 020
#define _IO_OCT 040
#define _IO_HEX 0100
#define _IO_SHOWBASE 0200
#define _IO_SHOWPOINT 0400
#define _IO_UPPERCASE 01000
#define _IO_SHOWPOS 02000
#define _IO_SCIENTIFIC 04000
#define _IO_FIXED 010000
#define _IO_UNITBUF 020000
#define _IO_STDIO 040000
#define _IO_DONT_CLOSE 0100000
#define _IO_BOOLALPHA 0200000
struct _IO_jump_t; struct _IO_FILE;
/* During the build of glibc itself, _IO_lock_t will already have been
defined by internal headers. */
#ifndef _IO_lock_t_defined
typedef void _IO_lock_t;
#endif
/* A streammarker remembers a position in a buffer. */
struct _IO_marker {
struct _IO_marker *_next;
struct _IO_FILE *_sbuf;
/* If _pos >= 0
it points to _buf->Gbase()+_pos. FIXME comment */
/* if _pos < 0, it points to _buf->eBptr()+_pos. FIXME comment */
int _pos;
#if 0
void set_streampos(streampos sp) { _spos = sp; }
void set_offset(int offset) { _pos = offset; _spos = (streampos)(-2); }
public:
streammarker(streambuf *sb);
~streammarker();
int saving() { return _spos == -2; }
int delta(streammarker&);
int delta();
#endif
};
/* This is the structure from the libstdc++ codecvt class. */
enum __codecvt_result
{
__codecvt_ok,
__codecvt_partial,
__codecvt_error,
__codecvt_noconv
};
#if defined _LIBC || defined _GLIBCPP_USE_WCHAR_T
/* The order of the elements in the following struct must match the order
of the virtual functions in the libstdc++ codecvt class. */
struct _IO_codecvt
{
void (*__codecvt_destr) (struct _IO_codecvt *);
enum __codecvt_result (*__codecvt_do_out) (struct _IO_codecvt *,
__mbstate_t *,
const wchar_t *,
const wchar_t *,
const wchar_t **, char *,
char *, char **);
enum __codecvt_result (*__codecvt_do_unshift) (struct _IO_codecvt *,
__mbstate_t *, char *,
char *, char **);
enum __codecvt_result (*__codecvt_do_in) (struct _IO_codecvt *,
__mbstate_t *,
const char *, const char *,
const char **, wchar_t *,
wchar_t *, wchar_t **);
int (*__codecvt_do_encoding) (struct _IO_codecvt *);
int (*__codecvt_do_always_noconv) (struct _IO_codecvt *);
int (*__codecvt_do_length) (struct _IO_codecvt *, __mbstate_t *,
const char *, const char *, _IO_size_t);
int (*__codecvt_do_max_length) (struct _IO_codecvt *);
_IO_iconv_t __cd_in;
_IO_iconv_t __cd_out;
};
/* Extra data for wide character streams. */
struct _IO_wide_data
{
wchar_t *_IO_read_ptr; /* Current read pointer */
wchar_t *_IO_read_end; /* End of get area. */
wchar_t *_IO_read_base; /* Start of putback+get area. */
wchar_t *_IO_write_base; /* Start of put area. */
wchar_t *_IO_write_ptr; /* Current put pointer. */
wchar_t *_IO_write_end; /* End of put area. */
wchar_t *_IO_buf_base; /* Start of reserve area. */
wchar_t *_IO_buf_end; /* End of reserve area. */
/* The following fields are used to support backing up and undo. */
wchar_t *_IO_save_base; /* Pointer to start of non-current get area. */
wchar_t *_IO_backup_base; /* Pointer to first valid character of
backup area */
wchar_t *_IO_save_end; /* Pointer to end of non-current get area. */
__mbstate_t _IO_state;
__mbstate_t _IO_last_state;
struct _IO_codecvt _codecvt;
wchar_t _shortbuf[1];
const struct _IO_jump_t *_wide_vtable;
};
#endif
struct _IO_FILE {
int _flags; /* High-order word is _IO_MAGIC; rest is flags. */
#define _IO_file_flags _flags
/* The following pointers correspond to the C++ streambuf protocol. */
/* Note: Tk uses the _IO_read_ptr and _IO_read_end fields directly. */
char* _IO_read_ptr; /* Current read pointer */
char* _IO_read_end; /* End of get area. */
char* _IO_read_base; /* Start of putback+get area. */
char* _IO_write_base; /* Start of put area. */
char* _IO_write_ptr; /* Current put pointer. */
char* _IO_write_end; /* End of put area. */
char* _IO_buf_base; /* Start of reserve area. */
char* _IO_buf_end; /* End of reserve area. */
/* The following fields are used to support backing up and undo. */
char *_IO_save_base; /* Pointer to start of non-current get area. */
char *_IO_backup_base; /* Pointer to first valid character of backup area */
char *_IO_save_end; /* Pointer to end of non-current get area. */
struct _IO_marker *_markers;
struct _IO_FILE *_chain;
int _fileno;
#if 0
int _blksize;
#else
int _flags2;
#endif
_IO_off_t _old_offset; /* This used to be _offset but it's too small. */
#define __HAVE_COLUMN /* temporary */
/* 1+column number of pbase(); 0 is unknown. */
unsigned short _cur_column;
signed char _vtable_offset;
char _shortbuf[1];
/* char* _save_gptr; char* _save_egptr; */
_IO_lock_t *_lock;
#ifdef _IO_USE_OLD_IO_FILE
};
struct _IO_FILE_complete
{
struct _IO_FILE _file;
#endif
#if defined _G_IO_IO_FILE_VERSION && _G_IO_IO_FILE_VERSION == 0x20001
_IO_off64_t _offset;
# if defined _LIBC || defined _GLIBCPP_USE_WCHAR_T
/* Wide character stream stuff. */
struct _IO_codecvt *_codecvt;
struct _IO_wide_data *_wide_data;
struct _IO_FILE *_freeres_list;
void *_freeres_buf;
# else
void *__pad1;
void *__pad2;
void *__pad3;
void *__pad4;
# endif
size_t __pad5;
int _mode;
/* Make sure we don't get into trouble again. */
char _unused2[15 * sizeof (int) - 4 * sizeof (void *) - sizeof (size_t)];
#endif
};
#ifndef __cplusplus
typedef struct _IO_FILE _IO_FILE;
#endif
struct _IO_FILE_plus;
extern struct _IO_FILE_plus _IO_2_1_stdin_;
extern struct _IO_FILE_plus _IO_2_1_stdout_;
extern struct _IO_FILE_plus _IO_2_1_stderr_;
#ifndef _LIBC
#define _IO_stdin ((_IO_FILE*)(&_IO_2_1_stdin_))
#define _IO_stdout ((_IO_FILE*)(&_IO_2_1_stdout_))
#define _IO_stderr ((_IO_FILE*)(&_IO_2_1_stderr_))
#else
extern _IO_FILE *_IO_stdin attribute_hidden;
extern _IO_FILE *_IO_stdout attribute_hidden;
extern _IO_FILE *_IO_stderr attribute_hidden;
#endif
/* Functions to do I/O and file management for a stream. */
/* Read NBYTES bytes from COOKIE into a buffer pointed to by BUF.
Return number of bytes read. */
typedef __ssize_t __io_read_fn (void *__cookie, char *__buf, size_t __nbytes);
/* Write N bytes pointed to by BUF to COOKIE. Write all N bytes
unless there is an error. Return number of bytes written. If
there is an error, return 0 and do not write anything. If the file
has been opened for append (__mode.__append set), then set the file
pointer to the end of the file and then do the write; if not, just
write at the current file pointer. */
typedef __ssize_t __io_write_fn (void *__cookie, const char *__buf,
size_t __n);
/* Move COOKIE's file position to *POS bytes from the
beginning of the file (if W is SEEK_SET),
the current position (if W is SEEK_CUR),
or the end of the file (if W is SEEK_END).
Set *POS to the new file position.
Returns zero if successful, nonzero if not. */
typedef int __io_seek_fn (void *__cookie, _IO_off64_t *__pos, int __w);
/* Close COOKIE. */
typedef int __io_close_fn (void *__cookie);
#ifdef __USE_GNU
/* User-visible names for the above. */
typedef __io_read_fn cookie_read_function_t;
typedef __io_write_fn cookie_write_function_t;
typedef __io_seek_fn cookie_seek_function_t;
typedef __io_close_fn cookie_close_function_t;
/* The structure with the cookie function pointers. */
typedef struct
{
__io_read_fn *read; /* Read bytes. */
__io_write_fn *write; /* Write bytes. */
__io_seek_fn *seek; /* Seek/tell file position. */
__io_close_fn *close; /* Close file. */
} _IO_cookie_io_functions_t;
typedef _IO_cookie_io_functions_t cookie_io_functions_t;
struct _IO_cookie_file;
/* Initialize one of those. */
extern void _IO_cookie_init (struct _IO_cookie_file *__cfile, int __read_write,
void *__cookie, _IO_cookie_io_functions_t __fns);
#endif
#ifdef __cplusplus
extern "C" {
#endif
extern int __underflow (_IO_FILE *);
extern int __uflow (_IO_FILE *);
extern int __overflow (_IO_FILE *, int);
#if defined _LIBC || defined _GLIBCPP_USE_WCHAR_T
extern _IO_wint_t __wunderflow (_IO_FILE *);
extern _IO_wint_t __wuflow (_IO_FILE *);
extern _IO_wint_t __woverflow (_IO_FILE *, _IO_wint_t);
#endif
#if __GNUC__ >= 3
# define _IO_BE(expr, res) __builtin_expect ((expr), res)
#else
# define _IO_BE(expr, res) (expr)
#endif
#define _IO_getc_unlocked(_fp) \
(_IO_BE ((_fp)->_IO_read_ptr >= (_fp)->_IO_read_end, 0) \
? __uflow (_fp) : *(unsigned char *) (_fp)->_IO_read_ptr++)
#define _IO_peekc_unlocked(_fp) \
(_IO_BE ((_fp)->_IO_read_ptr >= (_fp)->_IO_read_end, 0) \
&& __underflow (_fp) == EOF ? EOF \
: *(unsigned char *) (_fp)->_IO_read_ptr)
#define _IO_putc_unlocked(_ch, _fp) \
(_IO_BE ((_fp)->_IO_write_ptr >= (_fp)->_IO_write_end, 0) \
? __overflow (_fp, (unsigned char) (_ch)) \
: (unsigned char) (*(_fp)->_IO_write_ptr++ = (_ch)))
#if defined _LIBC || defined _GLIBCPP_USE_WCHAR_T
# define _IO_getwc_unlocked(_fp) \
(_IO_BE ((_fp)->_wide_data == NULL \
|| ((_fp)->_wide_data->_IO_read_ptr \
>= (_fp)->_wide_data->_IO_read_end), 0) \
? __wuflow (_fp) : (_IO_wint_t) *(_fp)->_wide_data->_IO_read_ptr++)
# define _IO_putwc_unlocked(_wch, _fp) \
(_IO_BE ((_fp)->_wide_data == NULL \
|| ((_fp)->_wide_data->_IO_write_ptr \
>= (_fp)->_wide_data->_IO_write_end), 0) \
? __woverflow (_fp, _wch) \
: (_IO_wint_t) (*(_fp)->_wide_data->_IO_write_ptr++ = (_wch)))
#endif
#define _IO_feof_unlocked(__fp) (((__fp)->_flags & _IO_EOF_SEEN) != 0)
#define _IO_ferror_unlocked(__fp) (((__fp)->_flags & _IO_ERR_SEEN) != 0)
extern int _IO_getc (_IO_FILE *__fp);
extern int _IO_putc (int __c, _IO_FILE *__fp);
extern int _IO_feof (_IO_FILE *__fp) __THROW;
extern int _IO_ferror (_IO_FILE *__fp) __THROW;
extern int _IO_peekc_locked (_IO_FILE *__fp);
/* This one is for Emacs. */
#define _IO_PENDING_OUTPUT_COUNT(_fp) \
((_fp)->_IO_write_ptr - (_fp)->_IO_write_base)
extern void _IO_flockfile (_IO_FILE *) __THROW;
extern void _IO_funlockfile (_IO_FILE *) __THROW;
extern int _IO_ftrylockfile (_IO_FILE *) __THROW;
#define _IO_peekc(_fp) _IO_peekc_unlocked (_fp)
#define _IO_flockfile(_fp) /**/
#define _IO_funlockfile(_fp) /**/
#define _IO_ftrylockfile(_fp) /**/
#ifndef _IO_cleanup_region_start
#define _IO_cleanup_region_start(_fct, _fp) /**/
#endif
#ifndef _IO_cleanup_region_end
#define _IO_cleanup_region_end(_Doit) /**/
#endif
#define _IO_need_lock(_fp) \
(((_fp)->_flags2 & _IO_FLAGS2_NEED_LOCK) != 0)
extern int _IO_vfscanf (_IO_FILE * __restrict, const char * __restrict,
_IO_va_list, int *__restrict);
extern int _IO_vfprintf (_IO_FILE *__restrict, const char *__restrict,
_IO_va_list);
extern _IO_ssize_t _IO_padn (_IO_FILE *, int, _IO_ssize_t);
extern _IO_size_t _IO_sgetn (_IO_FILE *, void *, _IO_size_t);
extern _IO_off64_t _IO_seekoff (_IO_FILE *, _IO_off64_t, int, int);
extern _IO_off64_t _IO_seekpos (_IO_FILE *, _IO_off64_t, int);
extern void _IO_free_backup_area (_IO_FILE *) __THROW;
#if defined _LIBC || defined _GLIBCPP_USE_WCHAR_T
extern _IO_wint_t _IO_getwc (_IO_FILE *__fp);
extern _IO_wint_t _IO_putwc (wchar_t __wc, _IO_FILE *__fp);
extern int _IO_fwide (_IO_FILE *__fp, int __mode) __THROW;
# if __GNUC__ >= 2
/* While compiling glibc we have to handle compatibility with very old
versions. */
# if defined _LIBC && defined SHARED
# include <shlib-compat.h>
# if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
# define _IO_fwide_maybe_incompatible \
(__builtin_expect (&_IO_stdin_used == NULL, 0))
extern const int _IO_stdin_used;
weak_extern (_IO_stdin_used);
# endif
# endif
# ifndef _IO_fwide_maybe_incompatible
# define _IO_fwide_maybe_incompatible (0)
# endif
/* A special optimized version of the function above. It optimizes the
case of initializing an unoriented byte stream. */
# define _IO_fwide(__fp, __mode) \
({ int __result = (__mode); \
if (__result < 0 && ! _IO_fwide_maybe_incompatible) \
{ \
if ((__fp)->_mode == 0) \
/* We know that all we have to do is to set the flag. */ \
(__fp)->_mode = -1; \
__result = (__fp)->_mode; \
} \
else if (__builtin_constant_p (__mode) && (__mode) == 0) \
__result = _IO_fwide_maybe_incompatible ? -1 : (__fp)->_mode; \
else \
__result = _IO_fwide (__fp, __result); \
__result; })
# endif
extern int _IO_vfwscanf (_IO_FILE * __restrict, const wchar_t * __restrict,
_IO_va_list, int *__restrict);
extern int _IO_vfwprintf (_IO_FILE *__restrict, const wchar_t *__restrict,
_IO_va_list);
extern _IO_ssize_t _IO_wpadn (_IO_FILE *, wint_t, _IO_ssize_t);
extern void _IO_free_wbackup_area (_IO_FILE *) __THROW;
#endif
#ifdef __LDBL_COMPAT
# include <bits/libio-ldbl.h>
#endif
#ifdef __cplusplus
}
#endif
#endif /* _IO_STDIO_H */
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