-.\" Hey Emacs! This file is -*- nroff -*- source.
-.\"
.\" Copyright (C) 2008 Michael Kerrisk <tmk.manpages@gmail.com>
.\" and Copyright 2003 Abhijit Menon-Sen <ams@wiw.org>
.\"
+.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
+.\" %%%LICENSE_END
.\"
.\" 2004-05-31, added tgkill, ahu, aeb
-.\" 2008-01-15 mtk -- rewote DESCRIPTION
+.\" 2008-01-15 mtk -- rewrote DESCRIPTION
.\"
-.TH TKILL 2 2008-10-01 "Linux" "Linux Programmer's Manual"
+.TH TKILL 2 2012-07-13 "Linux" "Linux Programmer's Manual"
.SH NAME
tkill, tgkill \- send a signal to a thread
.SH SYNOPSIS
.sp
.BI "int tgkill(int " tgid ", int " tid ", int " sig );
.fi
+
+.IR Note :
+There are no glibc wrappers for these system calls; see NOTES.
.SH DESCRIPTION
.BR tgkill ()
sends the signal
.IR tgid .
(By contrast,
.BR kill (2)
-can only be used to send a signal to a process (i.e., thread group)
+can be used to send a signal only to a process (i.e., thread group)
as a whole, and the signal will be delivered to an arbitrary
thread within that process.)
.BR tkill ()
is an obsolete predecessor to
.BR tgkill ().
-It only allows the target thread ID to be specified,
+It allows only the target thread ID to be specified,
which may result in the wrong thread being signaled if a thread
terminates and its thread ID is recycled.
Avoid using this system call.
+.\" FIXME: Maybe say something about the following:
+.\" http://sourceware.org/bugzilla/show_bug.cgi?id=12889
+.\" Rich Felker <bugdal@aerifal.cx>
+.\" There is a race condition in pthread_kill: it is possible that,
+.\" between the time pthread_kill reads the pid/tid from the target
+.\" thread descriptor and the time it makes the tgkill syscall,
+.\" the target thread terminates and the same tid gets assigned
+.\" to a new thread in the same process.
+.\"
+.\" (The tgkill syscall was designed to eliminate a similar race
+.\" condition in tkill, but it only succeeded in eliminating races
+.\" where the tid gets reused in a different process, and does not
+.\" help if the same tid gets assigned to a new thread in the
+.\" same process.)
+.\"
+.\" The only solution I can see is to introduce a mutex that ensures
+.\" that a thread cannot exit while pthread_kill is being called on it.
+.\"
+.\" Note that in most real-world situations, like almost all race
+.\" conditions, this one will be extremely rare. To make it
+.\" measurable, one could exhaust all but 1-2 available pid values,
+.\" possibly by lowering the max pid parameter in /proc, forcing
+.\" the same tid to be reused rapidly.
If
.I tgid
These are the raw system call interfaces, meant for internal
thread library use.
-.SH "RETURN VALUE"
+.SH RETURN VALUE
On success, zero is returned.
On error, \-1 is returned, and \fIerrno\fP
is set appropriately.
is supported since Linux 2.4.19 / 2.5.4.
.BR tgkill ()
was added in Linux 2.5.75.
-.SH "CONFORMING TO"
+.SH CONFORMING TO
.BR tkill ()
and
.BR tgkill ()
Glibc does not provide wrappers for these system calls; call them using
.BR syscall (2).
-.SH "SEE ALSO"
+.SH SEE ALSO
.BR clone (2),
.BR gettid (2),
-.BR kill (2)
+.BR kill (2),
+.BR rt_sigqueueinfo (2)
+.SH COLOPHON
+This page is part of release 3.65 of the Linux
+.I man-pages
+project.
+A description of the project,
+and information about reporting bugs,
+can be found at
+\%http://www.kernel.org/doc/man\-pages/.
OSDN Git Service
