TKILL(2)                  (2019-08-02)                   TKILL(2)

     NAME
          tkill, tgkill - send a signal to a thread

     SYNOPSIS
          int tkill(int tid, int sig);

          int tgkill(int tgid, int tid, int sig

          Note: There is no glibc wrapper for tkill(); see NOTES.

     DESCRIPTION
          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
          On success, zero is returned.  On error, -1 is returned, and
          errno is set appropriately.

     ERRORS
          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
               specified.

          EPERM
               Permission denied.  For the required permissions, see
               kill(2).

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

     Page 1                        Linux             (printed 5/24/22)

     TKILL(2)                  (2019-08-02)                   TKILL(2)

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

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

          Glibc does not provide a wrapper for tkill(); call it using
          syscall(2).  Before glibc 2.30, there was also no wrapper
          function for tgkill().

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

     COLOPHON
          This page is part of release 5.10 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/.

     Page 2                        Linux             (printed 5/24/22)