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| .\" FIXME Something could be added to this page (or exit(2)) |
| .\" about exit_robust_list processing |
| .\" |
| .TH GET_ROBUST_LIST 2 2015-12-28 Linux "Linux System Calls" |
| .SH NAME |
| get_robust_list, set_robust_list \- get/set list of robust futexes |
| .SH SYNOPSIS |
| .nf |
| .B #include <linux/futex.h> |
| .B #include <sys/types.h> |
| .B #include <syscall.h> |
| .sp |
| .BI "long get_robust_list(int " pid ", struct robust_list_head **" head_ptr , |
| .BI " size_t *" len_ptr ); |
| .BI "long set_robust_list(struct robust_list_head *" head ", size_t " len ); |
| .fi |
| |
| .IR Note : |
| There are no glibc wrappers for these system calls; see NOTES. |
| .SH 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 |
| .BR get_robust_list () |
| system call returns the head of the robust futex list of the thread |
| whose thread ID is specified in |
| .IR pid . |
| If |
| .I 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 |
| .IR head_ptr . |
| The size of the object pointed to by |
| .I **head_ptr |
| is stored in |
| .IR len_ptr . |
| |
| The |
| .BR set_robust_list () |
| system call requests the kernel to record the head of the list of |
| robust futexes owned by the calling thread. |
| The |
| .I head |
| argument is the list head to record. |
| The |
| .I len |
| argument should be |
| .IR sizeof(*head) . |
| .SH RETURN VALUE |
| The |
| .BR set_robust_list () |
| and |
| .BR get_robust_list () |
| system calls return zero when the operation is successful, |
| an error code otherwise. |
| .SH ERRORS |
| The |
| .BR set_robust_list () |
| system call can fail with the following error: |
| .TP |
| .B EINVAL |
| .I len |
| does not equal |
| .IR "sizeof(struct\ robust_list_head)" . |
| .PP |
| The |
| .BR get_robust_list () |
| system call can fail with the following errors: |
| .TP |
| .B EPERM |
| The calling process does not have permission to see the robust futex list of |
| the thread with the thread ID |
| .IR pid , |
| and does not have the |
| .BR CAP_SYS_PTRACE |
| capability. |
| .TP |
| .B ESRCH |
| No thread with the thread ID |
| .I pid |
| could be found. |
| .TP |
| .B EFAULT |
| The head of the robust futex list can't be stored at the location |
| .IR head . |
| .SH VERSIONS |
| These system calls were added in Linux 2.6.17. |
| .SH 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 |
| .BR 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. |
| .SH SEE ALSO |
| .BR futex (2) |
| .\" .BR pthread_mutexattr_setrobust_np (3) |
| |
| .IR Documentation/robust-futexes.txt |
| and |
| .IR Documentation/robust-futex-ABI.txt |
| in the Linux kernel source tree |
| .\" http://lwn.net/Articles/172149/ |