Originální popis anglicky:
set_tid_address - set pointer to thread ID
Návod, kniha: Linux Programmer's Manual
#include <linux/unistd.h>
long set_tid_address(int *tidptr);
The kernel keeps for each process two values called
set_child_tid and
clear_child_tid that are NULL by default.
If a process is started using
clone(2) with the
CLONE_CHILD_SETTID
flag,
set_child_tid is set to
child_tidptr, the fifth parameter
of that system call.
When
set_child_tid is set, the very first thing the new process does is
writing its PID at this address.
If a process is started using
clone(2) with the
CLONE_CHILD_CLEARTID flag,
clear_child_tid is set to
child_tidptr, the fifth parameter of that system call.
The system call
set_tid_address sets the
clear_child_tid value for
the calling process to
tidptr.
When
clear_child_tid is set, and the process exits, and the process was
sharing memory with other processes or threads, then 0 is written at this
address, and a
futex(child_tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); call
is done. (That is, wake a single process waiting on this futex.) Errors are
ignored.
set_tid_address returns the PID of the current process.
This call is present since Linux 2.5.48. Details as given here are valid since
Linux 2.5.49.
clone(2),
futex(2)
