Section: Linux System Calls (2)
get_robust_list, set_robust_list - get/set list of robust futexes
long get_robust_list(int pid, struct robust_list_head **head_ptr,
long set_robust_list(struct robust_list_head *head, size_t len);
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
The address of a thread'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
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
bit is set in the futex word, and the kernel performs a
operation on one of the threads waiting on the futex.
system call returns the head of the robust futex list of the thread
whose thread ID is specified in
the head of the list for the calling thread is returned.
The list head is stored in the location pointed to by
The size of the object pointed to by
is stored in
Permission to employ
is governed by a ptrace access mode
system call requests the kernel to record the head of the list of
robust futexes owned by the calling thread.
argument is the list head to record.
argument should be
system calls return zero when the operation is successful,
an error code otherwise.
system call can fail with the following error:
does not equal
system call can fail with the following errors:
The calling process does not have permission to see the robust futex list of
the thread with the thread ID
and does not have the
No thread with the thread ID
could be found.
The head of the robust futex list can't be stored at the location
These system calls were added in Linux 2.6.17.
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
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
The thread IDs mentioned in the main text are
thread IDs of the kind returned by
in the Linux kernel source tree
This page is part of release 5.02 of the Linux
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