tkill, tgkill - send a signal to a thread

#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).

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.

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

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