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tkill, tgkill - send a signal to a single process
_syscall2(int, tkill, int, tid, int, sig)
int tkill(int tid, int sig);
_syscall3(int, tgkill, int, tgid, int, tid, int, sig)
int tgkill(int tgid, int tid, int sig);
The tkill() system call is analogous to kill(2), except when the
specified process is part of a thread group (created by specifying the
CLONE_THREAD flag in the call to clone). Since all the processes in a
thread group have the same PID, they cannot be individually signalled
with kill(). With tkill(), however, one can address each process by
its unique TID.
The tgkill() call improves on tkill() by allowing the caller to specify
the thread group ID of the thread to be signalled, protecting against
TID reuse. If the tgid is specified as -1, tgkill() degenerates into
These are the raw system call interfaces, meant for internal thread
On success, zero is returned. On error, -1 is returned, and errno is
EINVAL An invalid TID 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)
tkill() and tgkill() are Linux specific and should not be used in
programs that are intended to be portable. tkill() is supported since
Linux 2.4.19 / 2.5.4. tgkill() was added in Linux 2.5.75.