get_robust_list(2)
NAME
get_robust_list, set_robust_list - get/set the list of robust futexes
SYNOPSIS
#include <linux/futex.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);
DESCRIPTION
The robust futex implementation needs to maintain per-thread lists of
robust futexes which are unlocked when the thread exits. These lists
are managed in user space, the kernel is only notified about the location of the head of the list.
get_robust_list returns the head of the robust futex list of the thread with TID defined by the pid argument. If pid is 0, the returned head belongs to the current thread. head_ptr is the pointer to the head of the list of robust futexes. The get_robust_list function stores the address of the head of the list here. len_ptr is the pointer to the length variable. get_robust_list stores sizeof(**head_ptr) here.
set_robust_list sets the head of the list of robust futexes owned by the current thread to head. len is the size of *head.
RETURN VALUE
The set_robust_list and get_robust_list functions return zero when the
operation is successful, an error code otherwise.
ERRORS
The set_robust_list function fails with EINVAL if the len value does
not match the size of structure struct robust_list_head expected by
kernel.
The get_robust_list function fails with EPERM if the current process
does not have permission to see the robust futex list of the thread
with the TID pid, ESRCH if a thread with the TID pid does not exist, or
EFAULT if the head of the robust futex list can't be stored in the
space specified by the head argument.
APPLICATION USAGE
A thread can have only one robust futex list; therefore applications
that wish to use this functionality should use robust mutexes provided
by glibc.
The system call is only available for debugging purposes and is not
needed for normal operations.
Both system calls are not available to application programs as functions; they can be called using the syscall(3) function.