tkill(2) — Linux manual page


TKILL(2)                Linux Programmer's Manual               TKILL(2)

NAME         top

       tkill, tgkill - send a signal to a thread

SYNOPSIS         top

       #include <signal.h>           /* Definition of SIG* constants */
       #include <sys/syscall.h>      /* Definition of SYS_* constants */
       #include <unistd.h>

       int syscall(SYS_tkill, pid_t tid, int sig);

       #include <signal.h>

       int tgkill(pid_t tgid, pid_t tid, int sig);

       Note: glibc provides no wrapper for tkill(), necessitating the
       use of syscall(2).

DESCRIPTION         top

       tgkill() sends the signal sig to the thread with the thread ID
       tid in the thread group tgid.  (By contrast, kill(2) can be used
       to send a signal only to a process (i.e., thread group) as a
       whole, and the signal will be delivered to an arbitrary thread
       within that process.)

       tkill() is an obsolete predecessor to tgkill().  It allows only
       the target thread ID to be specified, which may result in the
       wrong thread being signaled if a thread terminates and its thread
       ID is recycled.  Avoid using this system call.

       These are the raw system call interfaces, meant for internal
       thread library use.

RETURN VALUE         top

       On success, zero is returned.  On error, -1 is returned, and
       errno is set to indicate the error.

ERRORS         top

       EAGAIN The RLIMIT_SIGPENDING resource limit was reached and sig
              is a real-time signal.

       EAGAIN Insufficient kernel memory was available and sig is a
              real-time signal.

       EINVAL An invalid thread ID, thread group ID, or signal was

       EPERM  Permission denied.  For the required permissions, see

       ESRCH  No process with the specified thread ID (and thread group
              ID) exists.

VERSIONS         top

       tkill() is supported since Linux 2.4.19 / 2.5.4.  tgkill() was
       added in Linux 2.5.75.

       Library support for tgkill() was added to glibc in version 2.30.

CONFORMING TO         top

       tkill() and tgkill() are Linux-specific and should not be used in
       programs that are intended to be portable.

NOTES         top

       See the description of CLONE_THREAD in clone(2) for an
       explanation of thread groups.

       Before glibc 2.30, there was also no wrapper function for

SEE ALSO         top

       clone(2), gettid(2), kill(2), rt_sigqueueinfo(2)

COLOPHON         top

       This page is part of release 5.13 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

Linux                          2021-03-22                       TKILL(2)

Pages that refer to this page: clone(2)gettid(2)kill(2)ptrace(2)rt_sigqueueinfo(2)sigaction(2)syscalls(2)raise(3)nptl(7)signal(7)