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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | NOTES | SEE ALSO | COLOPHON |
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GET_ROBUST_LIST(2) Linux System Calls GET_ROBUST_LIST(2)
get_robust_list, set_robust_list - get/set list of robust futexes
#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: There are no glibc wrappers for these system calls; see NOTES.
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 set_robust_list(). The
address of a thread's robust futex list can be obtained using
get_robust_list().
The purpose of the robust futex list is to ensure that if a thread
accidentally fails to unlock a futex before terminating or calling
execve(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 FUTEX_OWNER_DIED bit is set in the futex
word, and the kernel performs a futex(2) FUTEX_WAKE operation on one
of the threads waiting on the futex.
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).
The set_robust_list() and get_robust_list() system calls return zero
when the operation is successful, an error code otherwise.
The set_robust_list() system call can fail with the following error:
EINVAL len does 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 the CAP_SYS_PTRACE capability.
ESRCH No thread with the thread ID pid could be found.
EFAULT The head of the robust futex list can't be stored at the
location head.
These system calls were added in Linux 2.6.17.
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.
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 execve(2).
The thread IDs mentioned in the main text are kernel thread IDs of
the kind returned by clone(2) and gettid(2).
futex(2), pthread_mutexattr_setrobust(3)
Documentation/robust-futexes.txt and Documentation/robust-futex-
ABI.txt in the Linux kernel source tree
This page is part of release 4.15 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/.
Linux 2017-09-15 GET_ROBUST_LIST(2)
Pages that refer to this page: execve(2), futex(2), gettid(2), ptrace(2), syscalls(2), exit(3), pthread_mutexattr_setrobust(3), capabilities(7), futex(7)
Copyright and license for this manual page
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