Section (2) get_robust_list
get_robust_list, set_robust_list — get/set list of robust futexes
#include <linux/futex.h> #include <sys/types.h> #include <syscall.h>
|struct robust_list_head **head_ptr,|
||struct robust_list_head *head,|
|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_zsingle_quotesz_s robust futex list can be obtained using
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.
call returns the head of the robust futex list of the thread
whose thread ID is specified in
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
Permission to employ
get_robust_list() is governed by a ptrace
PTRACE_MODE_READ_REALCREDS check; see
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
argument should be
get_robust_list() system calls
return zero when the operation is successful, an error code
call can fail with the following error:
lendoes not equal sizeof(struct robust_list_head).
call can fail with the following errors:
The head of the robust futex list can_zsingle_quotesz_t be stored at the location
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
No thread with the thread ID
pidcould be found.
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).
Documentation/robust-futex-ABI.txt in the
Linux kernel source tree
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Written by Ivana Varekova <varekovaredhat.com>
and Copyright (c) 2017, Michael Kerrisk <mtk.manpagesgmail.com>
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FIXME Something could be added to this page (or exit(2))
about exit_robust_list processing