NAME

       tkill, tgkill - send a signal to a thread

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

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

       [[deprecated]] 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

       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 to indicate  the
       error.

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.

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 in glibc 2.30.

STANDARDS

       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.

       Before glibc 2.30, there was also no wrapper function for tgkill().

SEE ALSO

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