Those flags were added in Linux 6.9 (see [1]), and are documented in [2]. The text added is a modified version of [3], removing some repetition and adapting from markdown to mandoc. [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e1fb1dc08e73 [2]: https://github.com/brauner/man-pages-md/blob/main/pidfd_send_signal.md [3]: https://github.com/brauner/man-pages-md/pull/2 Signed-off-by: Kir Kolyshkin <kolyshkin@xxxxxxxxx> --- man/man2/pidfd_send_signal.2 | 53 ++++++++++++++++++++++++++++++++++-- 1 file changed, 50 insertions(+), 3 deletions(-) diff --git a/man/man2/pidfd_send_signal.2 b/man/man2/pidfd_send_signal.2 index c7aecbf96..11d81dbe2 100644 --- a/man/man2/pidfd_send_signal.2 +++ b/man/man2/pidfd_send_signal.2 @@ -77,8 +77,55 @@ .SH DESCRIPTION .P The .I flags -argument is reserved for future use; -currently, this argument must be specified as 0. +argument allows to modify the scope of the signal. By +default, the scope of the signal will be inferred from the +. I pidfd +argument. For example, if +.I pidfd +refers to a specific thread, i.e., the +.I pidfd +was created through +.BR pidfd_open (2) +passing the +.B PIDFD_THREAD +flag +or through +.BR clone3 (2) +using the +.B CLONE_PIDFD +flag together with the +.B CLONE_THREAD +flag, then passing +.I pidfd to +.BR pidfd_send_signal (2) +and leaving the +.I flags argument as +.B 0 +will cause the signal to be sent to the specific thread referenced by the +.I pidfd. +.TP +.BR PIDFD_SIGNAL_THREAD " (since Linux v6.9)" +.\" commit e1fb1dc08e73466830612bcf2f9f72180965c9ba +Ensure that the signal is sent to the specific thread referenced by +.I pidfd. +.TP +.BR PIDFD_SIGNAL_THREAD_GROUP " (since Linux v6.9)" +.\" commit e1fb1dc08e73466830612bcf2f9f72180965c9ba +If +.I pidfd +refers to a thread-group leader, ensure that the signal is +sent to the thread-group, even if +.I pidfd +was created to refer to a specific thread. +.TP +.BR PIDFD_SIGNAL_PROCESS_GROUP " (since Linux v6.9)" +.\" commit e1fb1dc08e73466830612bcf2f9f72180965c9ba +If +.I pidfd +refers to a process-group leader, ensure that the signal is +sent to the process-group, even if +.I pidfd +was created to refer to a specific thread or to a thread-group leader. .SH RETURN VALUE On success, .BR pidfd_send_signal () @@ -102,7 +149,7 @@ .SH ERRORS .TP .B EINVAL .I flags -is not 0. +is not valid. .TP .B EPERM The calling process does not have permission to send the signal -- 2.45.2
