Manpages - tkill.2

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>

  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.

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.

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

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

This page is part of release 5.13 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/.