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SET_TID_ADDRESS(2) | Linux Programmer's Manual | SET_TID_ADDRESS(2) |
NAME¶
set_tid_address - set pointer to thread IDSYNOPSIS¶
#include <linux/unistd.h> long set_tid_address(int *tidptr);
DESCRIPTION¶
For each thread, the kernel maintains two attributes (addresses) called set_child_tid and clear_child_tid. These two attributes contain the value NULL by default.- set_child_tid
- If a thread is started using clone(2) with the CLONE_CHILD_SETTID flag, set_child_tid is set to the value passed in the ctid argument of that system call.
- When set_child_tid is set, the very first thing the new thread does is to write its thread ID at this address.
- clear_child_tid
- If a thread is started using clone(2) with the CLONE_CHILD_CLEARTID flag, clear_child_tid is set to the value passed in the ctid argument of that system call.
futex(clear_child_tid, FUTEX_WAKE, 1, NULL, NULL, 0); The effect of this operation is to wake a single thread that is performing a futex wait on the memory location. Errors from the futex wake operation are ignored.
RETURN VALUE¶
set_tid_address() always returns the caller's thread ID.ERRORS¶
set_tid_address() always succeeds.VERSIONS¶
This call is present since Linux 2.5.48. Details as given here are valid since Linux 2.5.49.CONFORMING TO¶
This system call is Linux-specific.SEE ALSO¶
clone(2), futex(2), gettid(2)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/.2014-07-08 | Linux |