Name
get_robust_list, set_robust_list — get/set list of robust futexes
Synopsis
#include <linux/futex.h> #include <sys/types.h> #include <syscall.h>
long
get_robust_list( |
int pid, |
| struct robust_list_head **head_ptr, | |
size_t *len_ptr); |
long
set_robust_list( |
struct robust_list_head *head, |
size_t len); |
![[Note]](../stylesheet/note.png) |
Note |
|---|---|
| There are no glibc wrappers for these system calls; see NOTES. |
DESCRIPTION
The robust futex implementation needs to maintain per-thread lists of the robust futexes which are to be unlocked when the thread exits. These lists are managed in user space; the kernel is notified about only the location of the head of the list.
The get_robust_list() system
call returns the head of the robust futex list of the thread
whose thread ID is specified in pid. If pid is 0, the head of the list
for the calling thread is returned. The list head is stored
in the location pointed to by head_ptr. The size of the
object pointed to by **head_ptr is stored in
len_ptr.
Permission to employ get_robust_list() is governed by a ptrace
access mode PTRACE_MODE_READ_REALCREDS check; see
ptrace(2).
The set_robust_list() system
call requests the kernel to record the head of the list of
robust futexes owned by the calling thread. The head argument is the list head
to record. The len
argument should be sizeof(*head).
RETURN VALUE
The set_robust_list() and
get_robust_list() system calls
return zero when the operation is successful, an error code
otherwise.
ERRORS
The set_robust_list() system
call can fail with the following error:
- EINVAL
-
lendoes not equal sizeof(struct robust_list_head).
The get_robust_list() system
call can fail with the following errors:
- EPERM
-
The calling process does not have permission to see the robust futex list of the thread with the thread ID
pid, and does not have theCAP_SYS_PTRACEcapability. - ESRCH
-
No thread with the thread ID
pidcould be found. - EFAULT
-
The head of the robust futex list can't be stored at the location
head.
NOTES
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 syscall(2).
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.
SEE ALSO
Documentation/robust-futexes.txt and
Documentation/robust-futex-ABI.txt in the
Linux kernel source tree
COLOPHON
This page is part of release 4.07 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
|
Copyright (C) 2006 Red Hat, Inc. All Rights Reserved. Written by Ivana Varekova <varekovaredhat.com> %%%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. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END FIXME Something could be added to this page (or exit(2)) about exit_robust_list processing |