178 lines
4.0 KiB
HTML
178 lines
4.0 KiB
HTML
|
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
|
<HTML><HEAD><TITLE>Man page of SET_TID_ADDRESS</TITLE>
|
|
</HEAD><BODY>
|
|
<H1>SET_TID_ADDRESS</H1>
|
|
Section: Linux Programmer's Manual (2)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
|
|
<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
|
|
|
|
<A NAME="lbAB"> </A>
|
|
<H2>NAME</H2>
|
|
|
|
set_tid_address - set pointer to thread ID
|
|
<A NAME="lbAC"> </A>
|
|
<H2>SYNOPSIS</H2>
|
|
|
|
<PRE>
|
|
<B>#include <<A HREF="file:///usr/include/linux/unistd.h">linux/unistd.h</A>></B>
|
|
|
|
<B>long set_tid_address(int *</B><I>tidptr</I><B>);</B>
|
|
</PRE>
|
|
|
|
<P>
|
|
|
|
<I>Note</I>:
|
|
|
|
There is no glibc wrapper for this system call; see NOTES.
|
|
<A NAME="lbAD"> </A>
|
|
<H2>DESCRIPTION</H2>
|
|
|
|
For each thread, the kernel maintains two attributes (addresses) called
|
|
<I>set_child_tid</I>
|
|
|
|
and
|
|
<I>clear_child_tid</I>.
|
|
|
|
These two attributes contain the value NULL by default.
|
|
<DL COMPACT>
|
|
<DT id="1"><I>set_child_tid</I>
|
|
|
|
<DD>
|
|
If a thread is started using
|
|
<B><A HREF="/cgi-bin/man/man2html?2+clone">clone</A></B>(2)
|
|
|
|
with the
|
|
<B>CLONE_CHILD_SETTID</B>
|
|
|
|
flag,
|
|
<I>set_child_tid</I>
|
|
|
|
is set to the value passed in the
|
|
<I>ctid</I>
|
|
|
|
argument of that system call.
|
|
<DT id="2"><DD>
|
|
When
|
|
<I>set_child_tid</I>
|
|
|
|
is set, the very first thing the new thread does
|
|
is to write its thread ID at this address.
|
|
<DT id="3"><I>clear_child_tid</I>
|
|
|
|
<DD>
|
|
If a thread is started using
|
|
<B><A HREF="/cgi-bin/man/man2html?2+clone">clone</A></B>(2)
|
|
|
|
with the
|
|
<B>CLONE_CHILD_CLEARTID</B>
|
|
|
|
flag,
|
|
<I>clear_child_tid</I>
|
|
|
|
is set to the value passed in the
|
|
<I>ctid</I>
|
|
|
|
argument of that system call.
|
|
</DL>
|
|
<P>
|
|
|
|
The system call
|
|
<B>set_tid_address</B>()
|
|
|
|
sets the
|
|
<I>clear_child_tid</I>
|
|
|
|
value for the calling thread to
|
|
<I>tidptr</I>.
|
|
|
|
<P>
|
|
|
|
When a thread whose
|
|
<I>clear_child_tid</I>
|
|
|
|
is not NULL terminates, then,
|
|
if the thread is sharing memory with other threads,
|
|
then 0 is written at the address specified in
|
|
<I>clear_child_tid</I>
|
|
|
|
and the kernel performs the following operation:
|
|
<P>
|
|
|
|
<BR> futex(clear_child_tid, FUTEX_WAKE, 1, NULL, NULL, 0);
|
|
<P>
|
|
|
|
The effect of this operation is to wake a single thread that
|
|
is performing a futex wait on the memory location.
|
|
Errors from the futex wake operation are ignored.
|
|
<A NAME="lbAE"> </A>
|
|
<H2>RETURN VALUE</H2>
|
|
|
|
<B>set_tid_address</B>()
|
|
|
|
always returns the caller's thread ID.
|
|
<A NAME="lbAF"> </A>
|
|
<H2>ERRORS</H2>
|
|
|
|
<B>set_tid_address</B>()
|
|
|
|
always succeeds.
|
|
<A NAME="lbAG"> </A>
|
|
<H2>VERSIONS</H2>
|
|
|
|
This call is present since Linux 2.5.48.
|
|
Details as given here are valid since Linux 2.5.49.
|
|
<A NAME="lbAH"> </A>
|
|
<H2>CONFORMING TO</H2>
|
|
|
|
This system call is Linux-specific.
|
|
<A NAME="lbAI"> </A>
|
|
<H2>NOTES</H2>
|
|
|
|
Glibc does not provide a wrapper for this system call; call it using
|
|
<B><A HREF="/cgi-bin/man/man2html?2+syscall">syscall</A></B>(2).
|
|
|
|
<A NAME="lbAJ"> </A>
|
|
<H2>SEE ALSO</H2>
|
|
|
|
<B><A HREF="/cgi-bin/man/man2html?2+clone">clone</A></B>(2),
|
|
|
|
<B><A HREF="/cgi-bin/man/man2html?2+futex">futex</A></B>(2),
|
|
|
|
<B><A HREF="/cgi-bin/man/man2html?2+gettid">gettid</A></B>(2)
|
|
|
|
<A NAME="lbAK"> </A>
|
|
<H2>COLOPHON</H2>
|
|
|
|
This page is part of release 5.05 of the Linux
|
|
<I>man-pages</I>
|
|
|
|
project.
|
|
A description of the project,
|
|
information about reporting bugs,
|
|
and the latest version of this page,
|
|
can be found at
|
|
<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
|
|
<P>
|
|
|
|
<HR>
|
|
<A NAME="index"> </A><H2>Index</H2>
|
|
<DL>
|
|
<DT id="4"><A HREF="#lbAB">NAME</A><DD>
|
|
<DT id="5"><A HREF="#lbAC">SYNOPSIS</A><DD>
|
|
<DT id="6"><A HREF="#lbAD">DESCRIPTION</A><DD>
|
|
<DT id="7"><A HREF="#lbAE">RETURN VALUE</A><DD>
|
|
<DT id="8"><A HREF="#lbAF">ERRORS</A><DD>
|
|
<DT id="9"><A HREF="#lbAG">VERSIONS</A><DD>
|
|
<DT id="10"><A HREF="#lbAH">CONFORMING TO</A><DD>
|
|
<DT id="11"><A HREF="#lbAI">NOTES</A><DD>
|
|
<DT id="12"><A HREF="#lbAJ">SEE ALSO</A><DD>
|
|
<DT id="13"><A HREF="#lbAK">COLOPHON</A><DD>
|
|
</DL>
|
|
<HR>
|
|
This document was created by
|
|
<A HREF="/cgi-bin/man/man2html">man2html</A>,
|
|
using the manual pages.<BR>
|
|
Time: 00:05:34 GMT, March 31, 2021
|
|
</BODY>
|
|
</HTML>
|