NAME
pthread_kill —
send a signal to a thread
SYNOPSIS
int pthread_kill(pthread_t thread, int sig);
DESCRIPTION
The pthread_kill () function shall request
that a signal be delivered to the specified thread. It shall not be an error
if
thread
is a zombie thread.
RETURN VALUE
Upon successful completion, the function shall return a value of
zero. Otherwise, the function shall return an error number. If the
pthread_kill () function fails, no signal shall be
sent.
ERRORS
The pthread_kill () function may fail
if:
- [EINVAL]
- The value of the sig argument is zero.
The pthread_kill () function shall fail
if:
- [EINVAL]
- The value of the sig argument is non-zero and is an invalid or unsupported signal number.
The pthread_kill () function shall not
return an error code of [EINTR].
EXAMPLES
None.
APPLICATION USAGE
The pthread_kill () function provides a
mechanism for asynchronously directing a signal at a thread in the calling
process. This could be used, for example, by one thread to affect broadcast
delivery of a signal to a set of threads.
Note that pthread_kill () only causes the
signal to be handled in the context of the given thread; the signal action
(termination or stopping) affects the process as a whole.
RATIONALE
If an implementation detects use of a thread ID after the end of its lifetime, it is recommended that the function should fail and report an [ESRCH] error.
Historical implementations varied on the result of a
pthread_kill () with a thread ID indicating a zombie
thread. Some indicated success on such a call, while others gave an error of
[ESRCH]. Since the definition of thread lifetime in this volume of
POSIX.1-2024 covers zombie threads, the [ESRCH] error as described is
inappropriate in this case and implementations that give this error do not
conform. In particular, this means that an application cannot have one
thread check for termination of another by calling
pthread_kill () with a sig
argument of zero, and implementations may indicate that it is not possible
by returning [EINVAL] when sig is zero.
FUTURE DIRECTIONS
None.
SEE ALSO
kill(3), pthread_self(3), raise(3)
XBD <signal.h>
CHANGE HISTORY
First released in Issue 5. Included for alignment with the POSIX Threads Extension.
Issue 6
The pthread_kill () function is marked as
part of the Threads option.
The APPLICATION USAGE section is added.
Issue 7
The pthread_kill () function is moved from
the Threads option to the Base.
Austin Group Interpretation 1003.1-2001 #142 is applied, removing the [ESRCH] error condition.
POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0277 [765] is applied.
Issue 8
Austin Group Defect 792 is applied, adding a requirement that
passing the thread ID of a zombie thread to
pthread_kill () is not treated as an error.
Austin Group Defect 1214 is applied, allowing
pthread_kill () to fail with [EINVAL] when the
sig argument is zero.