GET_ROBUST_LIST(2)	      Linux System Calls	    GET_ROBUST_LIST(2)



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.

       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).

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 loca-
	      tion 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 pro-
       vided 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 4.10 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				  2016-07-17		    GET_ROBUST_LIST(2)