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       tkill, tgkill - send a signal to a thread


       int tkill(int tid, int sig);

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

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


       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

       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.


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


       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.


       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.


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


       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().


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


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