259 lines
6.0 KiB
HTML
259 lines
6.0 KiB
HTML
|
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
|
<HTML><HEAD><TITLE>Man page of GET_ROBUST_LIST</TITLE>
|
|
</HEAD><BODY>
|
|
<H1>GET_ROBUST_LIST</H1>
|
|
Section: Linux System Calls (2)<BR>Updated: 2019-10-10<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>
|
|
|
|
get_robust_list, set_robust_list - get/set list of robust futexes
|
|
<A NAME="lbAC"> </A>
|
|
<H2>SYNOPSIS</H2>
|
|
|
|
<PRE>
|
|
<B>#include <<A HREF="file:///usr/include/linux/futex.h">linux/futex.h</A>></B>
|
|
<B>#include <<A HREF="file:///usr/include/sys/types.h">sys/types.h</A>></B>
|
|
<B>#include <<A HREF="file:///usr/include/syscall.h">syscall.h</A>></B>
|
|
|
|
<B>long get_robust_list(int </B><I>pid</I><B>, struct robust_list_head **</B><I>head_ptr</I><B>,</B>
|
|
<B> size_t *</B><I>len_ptr</I><B>);</B>
|
|
<B>long set_robust_list(struct robust_list_head *</B><I>head</I><B>, size_t </B><I>len</I><B>);</B>
|
|
</PRE>
|
|
|
|
<P>
|
|
|
|
<I>Note</I>:
|
|
|
|
There are no glibc wrappers for these system calls; see NOTES.
|
|
<A NAME="lbAD"> </A>
|
|
<H2>DESCRIPTION</H2>
|
|
|
|
These system calls deal with per-thread robust futex lists.
|
|
These lists are managed in user space:
|
|
the kernel knows only about the location of the head of the list.
|
|
A thread can inform the kernel of the location of its robust futex list using
|
|
<B>set_robust_list</B>().
|
|
|
|
The address of a thread's robust futex list can be obtained using
|
|
<B>get_robust_list</B>().
|
|
|
|
<P>
|
|
|
|
The purpose of the robust futex list is to ensure that if a thread
|
|
accidentally fails to unlock a futex before terminating or calling
|
|
<B><A HREF="/cgi-bin/man/man2html?2+execve">execve</A></B>(2),
|
|
|
|
another thread that is waiting on that futex is notified that
|
|
the former owner of the futex has died.
|
|
This notification consists of two pieces: the
|
|
<B>FUTEX_OWNER_DIED</B>
|
|
|
|
bit is set in the futex word, and the kernel performs a
|
|
<B><A HREF="/cgi-bin/man/man2html?2+futex">futex</A></B>(2)
|
|
|
|
<B>FUTEX_WAKE</B>
|
|
|
|
operation on one of the threads waiting on the futex.
|
|
<P>
|
|
|
|
The
|
|
<B>get_robust_list</B>()
|
|
|
|
system call returns the head of the robust futex list of the thread
|
|
whose thread ID is specified in
|
|
<I>pid</I>.
|
|
|
|
If
|
|
<I>pid</I>
|
|
|
|
is 0,
|
|
the head of the list for the calling thread is returned.
|
|
The list head is stored in the location pointed to by
|
|
<I>head_ptr</I>.
|
|
|
|
The size of the object pointed to by
|
|
<I>**head_ptr</I>
|
|
|
|
is stored in
|
|
<I>len_ptr</I>.
|
|
|
|
<P>
|
|
|
|
Permission to employ
|
|
<B>get_robust_list</B>()
|
|
|
|
is governed by a ptrace access mode
|
|
<B>PTRACE_MODE_READ_REALCREDS</B>
|
|
|
|
check; see
|
|
<B><A HREF="/cgi-bin/man/man2html?2+ptrace">ptrace</A></B>(2).
|
|
|
|
<P>
|
|
|
|
The
|
|
<B>set_robust_list</B>()
|
|
|
|
system call requests the kernel to record the head of the list of
|
|
robust futexes owned by the calling thread.
|
|
The
|
|
<I>head</I>
|
|
|
|
argument is the list head to record.
|
|
The
|
|
<I>len</I>
|
|
|
|
argument should be
|
|
<I>sizeof(*head)</I>.
|
|
|
|
<A NAME="lbAE"> </A>
|
|
<H2>RETURN VALUE</H2>
|
|
|
|
The
|
|
<B>set_robust_list</B>()
|
|
|
|
and
|
|
<B>get_robust_list</B>()
|
|
|
|
system calls return zero when the operation is successful,
|
|
an error code otherwise.
|
|
<A NAME="lbAF"> </A>
|
|
<H2>ERRORS</H2>
|
|
|
|
The
|
|
<B>set_robust_list</B>()
|
|
|
|
system call can fail with the following error:
|
|
<DL COMPACT>
|
|
<DT id="1"><B>EINVAL</B>
|
|
|
|
<DD>
|
|
<I>len</I>
|
|
|
|
does not equal
|
|
<I>sizeof(struct robust_list_head)</I>.
|
|
|
|
</DL>
|
|
<P>
|
|
|
|
The
|
|
<B>get_robust_list</B>()
|
|
|
|
system call can fail with the following errors:
|
|
<DL COMPACT>
|
|
<DT id="2"><B>EFAULT</B>
|
|
|
|
<DD>
|
|
The head of the robust futex list can't be stored at the location
|
|
<I>head</I>.
|
|
|
|
<DT id="3"><B>EPERM</B>
|
|
|
|
<DD>
|
|
The calling process does not have permission to see the robust futex list of
|
|
the thread with the thread ID
|
|
<I>pid</I>,
|
|
|
|
and does not have the
|
|
<B>CAP_SYS_PTRACE</B>
|
|
|
|
capability.
|
|
<DT id="4"><B>ESRCH</B>
|
|
|
|
<DD>
|
|
No thread with the thread ID
|
|
<I>pid</I>
|
|
|
|
could be found.
|
|
</DL>
|
|
<A NAME="lbAG"> </A>
|
|
<H2>VERSIONS</H2>
|
|
|
|
These system calls were added in Linux 2.6.17.
|
|
<A NAME="lbAH"> </A>
|
|
<H2>NOTES</H2>
|
|
|
|
These system calls are not needed by normal applications.
|
|
No support for them is provided in glibc.
|
|
In the unlikely event that you want to call them directly, use
|
|
<B><A HREF="/cgi-bin/man/man2html?2+syscall">syscall</A></B>(2).
|
|
|
|
<P>
|
|
|
|
A thread can have only one robust futex list;
|
|
therefore applications that wish
|
|
to use this functionality should use the robust mutexes provided by glibc.
|
|
<P>
|
|
|
|
In the initial implementation,
|
|
a thread waiting on a futex was notified that the owner had died
|
|
only if the owner terminated.
|
|
Starting with Linux 2.6.28,
|
|
|
|
notification was extended to include the case where the owner performs an
|
|
<B><A HREF="/cgi-bin/man/man2html?2+execve">execve</A></B>(2).
|
|
|
|
<P>
|
|
|
|
The thread IDs mentioned in the main text are
|
|
<I>kernel</I>
|
|
|
|
thread IDs of the kind returned by
|
|
<B><A HREF="/cgi-bin/man/man2html?2+clone">clone</A></B>(2)
|
|
|
|
and
|
|
<B><A HREF="/cgi-bin/man/man2html?2+gettid">gettid</A></B>(2).
|
|
|
|
<A NAME="lbAI"> </A>
|
|
<H2>SEE ALSO</H2>
|
|
|
|
<B><A HREF="/cgi-bin/man/man2html?2+futex">futex</A></B>(2),
|
|
|
|
<B><A HREF="/cgi-bin/man/man2html?3+pthread_mutexattr_setrobust">pthread_mutexattr_setrobust</A></B>(3)
|
|
|
|
<P>
|
|
|
|
<I>Documentation/robust-futexes.txt</I>
|
|
|
|
and
|
|
<I>Documentation/robust-futex-ABI.txt</I>
|
|
|
|
in the Linux kernel source tree
|
|
|
|
<A NAME="lbAJ"> </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="5"><A HREF="#lbAB">NAME</A><DD>
|
|
<DT id="6"><A HREF="#lbAC">SYNOPSIS</A><DD>
|
|
<DT id="7"><A HREF="#lbAD">DESCRIPTION</A><DD>
|
|
<DT id="8"><A HREF="#lbAE">RETURN VALUE</A><DD>
|
|
<DT id="9"><A HREF="#lbAF">ERRORS</A><DD>
|
|
<DT id="10"><A HREF="#lbAG">VERSIONS</A><DD>
|
|
<DT id="11"><A HREF="#lbAH">NOTES</A><DD>
|
|
<DT id="12"><A HREF="#lbAI">SEE ALSO</A><DD>
|
|
<DT id="13"><A HREF="#lbAJ">COLOPHON</A><DD>
|
|
</DL>
|
|
<HR>
|
|
This document was created by
|
|
<A HREF="/cgi-bin/man/man2html">man2html</A>,
|
|
using the manual pages.<BR>
|
|
Time: 00:05:32 GMT, March 31, 2021
|
|
</BODY>
|
|
</HTML>
|