set_tid_address: nastavit ukazatel na ID vlákna

Originální popis anglicky: set_tid_address - set pointer to thread ID

Návod, kniha: Linux Programmer's Manual

STRUČNĚ

#include <linux/unistd.h>
 
long set_tid_address(int *tidptr);

POPIS / INSTRUKCE

The kernel keeps for each process two values called set_child_tid and clear_child_tid that are NULL by default.

set_child_tid

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.

clear_child_tid

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.

NÁVRATOVÁ HODNOTA

set_tid_address returns the PID of the current process.

HISTORY

This call is present since Linux 2.5.48. Details as given here are valid since Linux 2.5.49.

SOUVISEJÍCÍ

clone(2), futex(2)