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NAME

       get_robust_list, set_robust_list - get/set 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);

       Note: There are no glibc wrappers for these system calls; see NOTES.

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 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 match the size of structure struct robust_list_head
              expected by kernel.

       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.  No library  support  is
       provided; use syscall(2).

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 3.65 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



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