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: 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.

       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 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.

VERSIONS

       These system calls were added in Linux 2.6.17.

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

       futex(2)

       Documentation/robust-futexes.txt  and  Documentation/robust-futex-ABI.txt  in  the   Linux
       kernel source tree

COLOPHON

       This  page  is  part of release 4.04 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 http://www.kernel.org/doc/man-pages/.