Add a manual page for flockfile(3) etc.; while here, also add *_unlocked()

to stdio(3) overview documentation.  Fixes PR lib/20096 from Jason Thorpe.

lib/libc/stdio/Makefile.inc

@@ -1,5 +1,5 @@
 #	from: @(#)Makefile.inc	5.7 (Berkeley) 6/27/91
-#	$NetBSD: Makefile.inc,v 1.23 2003/01/18 11:29:50 thorpej Exp $
+#	$NetBSD: Makefile.inc,v 1.24 2003/01/28 20:26:04 kleink Exp $
 
 # stdio sources
 .PATH: ${.CURDIR}/stdio
@@ -26,13 +26,14 @@ SRCS+=	gets.c sprintf.c vsprintf.c tempnam.c tmpnam.c mktemp.c
 # namespace purity wrappers
 SRCS+=	_fseeko.c _ftello.c
 
-MAN+=	fclose.3 ferror.3 fflush.3 fgetln.3 fgets.3 fopen.3 fputs.3 \
+MAN+=	fclose.3 ferror.3 fflush.3 fgetln.3 fgets.3 flockfile.3 fopen.3 \
-	fread.3 fseek.3 funopen.3 getc.3 mktemp.3 perror.3 printf.3 putc.3 \
+	fputs.3 fread.3 fseek.3 funopen.3 getc.3 mktemp.3 perror.3 printf.3 \
-	remove.3 scanf.3 setbuf.3 stdio.3 tmpnam.3 ungetc.3 putwc.3 getwc.3 \
+	putc.3 remove.3 scanf.3 setbuf.3 stdio.3 tmpnam.3 ungetc.3 putwc.3 \
-	ungetwc.3 fwide.3 fparseln.3
+	getwc.3 ungetwc.3 fwide.3 fparseln.3
 
 MLINKS+=ferror.3 clearerr.3 ferror.3 feof.3 ferror.3 fileno.3
 MLINKS+=fflush.3 fpurge.3
+MLINKS+=flockfile.3 ftrylockfile.3 flockfile.3 funlockfile.3
 MLINKS+=fgets.3 gets.3
 MLINKS+=fopen.3 fdopen.3 fopen.3 freopen.3
 MLINKS+=fputs.3 puts.3

lib/libc/stdio/flockfile.3

@@ -0,0 +1,127 @@
+.\"	$NetBSD: flockfile.3,v 1.1 2003/01/28 20:26:04 kleink Exp $
+.\"
+.\" Copyright (c) 2003 The NetBSD Foundation, Inc.
+.\" All rights reserved.
+.\"
+.\" This code is derived from software contributed to The NetBSD Foundation
+.\" by Klaus Klein.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\"    must display the following acknowledgement:
+.\"        This product includes software developed by the NetBSD
+.\"        Foundation, Inc. and its contributors.
+.\" 4. Neither the name of The NetBSD Foundation nor the names of its
+.\"    contributors may be used to endorse or promote products derived
+.\"    from this software without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+.\" PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+.\" POSSIBILITY OF SUCH DAMAGE.
+.\"
+.Dd January 28, 2003
+.Dt FLOCKFILE 3
+.Os
+.Sh NAME
+.Nm flockfile ,
+.Nm ftrylockfile ,
+.Nm funlockfile
+.Nd stdio stream locking functions
+.Sh LIBRARY
+.Lb libc
+.Sh SYNOPSIS
+.Fd #include \*[Lt]stdio.h\*[Gt]
+.Ft void
+.Fn flockfile "FILE *file"
+.Ft int
+.Fn ftrylockfile "FILE *file"
+.Ft void
+.Fn funlockfile "FILE *file"
+.Sh DESCRIPTION
+The
+.Fn flockfile ,
+.Fn ftrylockfile
+and
+.Fn funlockfile
+functions provide applications with explicit control of locking of
+stdio stream objects.
+They can be used by a thread to execute a sequence of I/O operations
+as a unit, without interference from another thread.
+.Pp
+Locks on stdio streams are recursive, and a lock count is maintained.
+stdio streams are created unlocked, with a lock count of zero.
+After successful acquisition of the lock, its count is incremented
+to one, indicating locked state of the stdio stream.
+Each subsequent relock operation performed by the owner thread
+increments the lock count by one, and each subsequent unlock
+operation performed by the owner thread decrements the lock count by one,
+allowing matching lock and unlock operations to be nested.
+After its lock count is decremented to zero, the stdio stream returns
+to unlocked state, and ownership of the stdio stream is relinquished.
+.Pp
+The
+.Fn flockfile
+function acquires the ownership of
+.Fa file
+for the calling thread.
+If
+.Fa file
+is already owned by another thread, the calling thread is suspended
+until the acquisition is possible (i.e.,
+.Fa file
+is relinquished again and the calling thread is scheduled to acquire it).
+.Pp
+The
+.Fn ftrylockfile
+function acquires the ownership of
+.Fa file
+for the calling thread only if
+.Fa file
+is available.
+.Pp
+The
+.Fn funlockfile
+function relinquishes the ownership of
+.Fa file
+previously granted to the calling thread.
+Only the current owner of
+.Fa file
+may
+.Fn funlockfile
+it.
+.Sh RETURN VALUES
+If successful, the
+.Fn ftrylockfile
+function returns 0.
+Otherwise, it returns non-zero to indicate that the lock cannot be acquired.
+.Sh SEE ALSO
+.Xr getc_unlocked 3 ,
+.Xr getchar_unlocked 3 ,
+.Xr putc_unlocked 3 ,
+.Xr putchar_unlocked 3
+.Sh STANDARDS
+The
+.Fn flockfile ,
+.Fn ftrylockfile
+and
+.Fn funlockfile
+functions conform to
+.St -p1003.1-2001 .
+.Sh BUGS
+The design of these interfaces does not allow for addressing the
+problem of priority inversion.

lib/libc/stdio/getc.3

@@ -1,4 +1,4 @@
-.\"	$NetBSD: getc.3,v 1.9 2003/01/18 11:29:55 thorpej Exp $
+.\"	$NetBSD: getc.3,v 1.10 2003/01/28 20:26:04 kleink Exp $
 .\"
 .\" Copyright (c) 1990, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -136,8 +136,11 @@ until the condition is cleared with
 .Xr clearerr 3 .
 .Sh SEE ALSO
 .Xr ferror 3 ,
+.Xr flockfile 3 ,
 .Xr fopen 3 ,
 .Xr fread 3 ,
+.Xr ftrylockfile 3 ,
+.Xr funlockfile 3 ,
 .Xr putc 3 ,
 .Xr ungetc 3
 .Sh STANDARDS

lib/libc/stdio/stdio.3

@@ -1,4 +1,4 @@
-.\"	$NetBSD: stdio.3,v 1.16 2003/01/18 11:29:58 thorpej Exp $
+.\"	$NetBSD: stdio.3,v 1.17 2003/01/28 20:26:04 kleink Exp $
 .\"
 .\" Copyright (c) 1990, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -33,7 +33,7 @@
 .\"
 .\"     @(#)stdio.3	8.7 (Berkeley) 4/19/94
 .\"
-.Dd April 19, 1994
+.Dd January 28, 2003
 .Dt STDIO 3
 .Os
 .Sh NAME
@@ -168,6 +168,21 @@ sections of the following manual pages indicate which include files
 are to be used, what the compiler declaration for the function
 looks like and which external variables are of interest.
 .Pp
+In multi-threaded applications, operations on streams perform implicit
+locking, except for the
+.Fa getc_unlocked ,
+.Fa getchar_unlocked ,
+.Fa putc_unlocked ,
+and
+.Fa putchar_unlocked
+functions.
+Explicit control of stream locking is available through the
+.Fa flockfile ,
+.Fa ftrylockfile ,
+and
+.Fa funlockfile
+functions .
+.Pp
 The following are defined as macros; these names may not be re-used
 without first removing their current definitions with
 .Dv #undef :
@@ -190,9 +205,13 @@ without first removing their current definitions with
 .Fn freopen ,
 .Fn fwopen ,
 .Fn getc ,
+.Fn getc_unlocked ,
 .Fn getchar ,
+.Fn getchar_unlocked ,
 .Fn putc ,
+.Fn putc_unlocked ,
 .Fn putchar ,
+.Fn putchar_unlocked ,
 .Dv stderr ,
 .Dv stdin ,
 .Dv stdout .
@@ -202,10 +221,14 @@ Function versions of the macro functions
 .Fn clearerr ,
 .Fn fileno ,
 .Fn getc ,
+.Fn getc_unlocked ,
 .Fn getchar ,
+.Fn getchar_unlocked ,
 .Fn putc ,
+.Fn putc_unlocked ,
+.Fn putchar ,
 and
-.Fn putchar
+.Fn putchar_unlocked
 exist and will be used if the macros definitions are explicitly removed.
 .Sh SEE ALSO
 .Xr close 2 ,
@@ -218,7 +241,7 @@ The
 library conforms to
 .St -ansiC .
 .Sh LIST OF FUNCTIONS
-.Bl -column "Description"
+.Bl -column "Functionxxxxxxxx" "Description"
 .Sy Function	Description
 clearerr	check and reset stream status
 fclose	close a stream
@@ -232,6 +255,7 @@ fgetpos	reposition a stream
 fgets	get a line from a stream
 fgetwc	get next wide character from input stream
 fileno	check and reset stream status
+flockfile	lock a stream
 fopen	stream open functions
 fprintf	formatted output conversion
 fpurge	flush a stream
@@ -245,12 +269,18 @@ fscanf	input format conversion
 fseek	reposition a stream
 fsetpos	reposition a stream
 ftell	reposition a stream
+ftrylockfile	lock a stream (non-blocking)
+funlockfile	unlock a stream
 funopen	open a stream
 fwide	set/get orientation of a stream
 fwopen	open a stream
 fwrite	binary stream input/output
 getc	get next character or word from input stream
+getc_unlocked	get next character or word from input stream
+	(no implicit locking)
 getchar	get next character or word from input stream
+getchar_unlocked	get next character or word from input stream
+	(no implicit locking)
 gets	get a line from a stream
 getw	get next character or word from input stream
 getwc	get next wide character from input stream
@@ -260,7 +290,11 @@ mktemp	create unique temporary file
 perror	system error messages
 printf	formatted output conversion
 putc	output a character or word to a stream
+putc_unlocked	output a character or word to a stream
+	(no implicit locking)
 putchar	output a character or word to a stream
+putchar_unlocked	output a character or word to a stream
+	(no implicit locking)
 puts	output a line to a stream
 putw	output a character or word to a stream
 putwc	output a wide character to a stream