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.TH RT_SIGQUEUEINFO 2 2017-09-15 "Linux" "Linux Programmer's Manual"
.SH NAME
rt_sigqueueinfo, rt_tgsigqueueinfo \- queue a signal and data
.SH SYNOPSIS
.nf
.BI "int rt_sigqueueinfo(pid_t " tgid ", int " sig ", siginfo_t *" uinfo );
.PP
.BI "int rt_tgsigqueueinfo(pid_t " tgid ", pid_t " tid ", int " sig ,
.BI "                      siginfo_t *" uinfo );
.fi
.PP
.IR Note :
There are no glibc wrappers for these system calls; see NOTES.
.SH DESCRIPTION
The
.BR rt_sigqueueinfo ()
and
.BR rt_tgsigqueueinfo ()
system calls are the low-level interfaces used to send a signal plus data
to a process or thread.
The receiver of the signal can obtain the accompanying data
by establishing a signal handler with the
.BR sigaction (2)
.B SA_SIGINFO
flag.
.PP
These system calls are not intended for direct application use;
they are provided to allow the implementation of
.BR sigqueue (3)
and
.BR pthread_sigqueue (3).
.PP
The
.BR rt_sigqueueinfo ()
system call sends the signal
.I sig
to the thread group with the ID
.IR tgid .
(The term "thread group" is synonymous with "process", and
.I tid
corresponds to the traditional UNIX process ID.)
The signal will be delivered to an arbitrary member of the thread group
(i.e., one of the threads that is not currently blocking the signal).
.PP
The
.I uinfo
argument specifies the data to accompany the signal.
This argument is a pointer to a structure of type
.IR siginfo_t ,
described in
.BR sigaction (2)
(and defined by including
.IR <sigaction.h> ).
The caller should set the following fields in this structure:
.TP
.I si_code
This must be one of the
.B SI_*
codes in the Linux kernel source file
.IR include/asm-generic/siginfo.h ,
with the restriction that the code must be negative
(i.e., cannot be
.BR SI_USER ,
which is used by the kernel to indicate a signal sent by
.BR kill (2))
and cannot (since Linux 2.6.39) be
.BR SI_TKILL
(which is used by the kernel to indicate a signal sent using
.\" tkill(2) or
.BR tgkill (2)).
.TP
.I si_pid
This should be set to a process ID,
typically the process ID of the sender.
.TP
.I si_uid
This should be set to a user ID,
typically the real user ID of the sender.
.TP
.I si_value
This field contains the user data to accompany the signal.
For more information, see the description of the last
.RI ( "union sigval" )
argument of
.BR sigqueue (3).
.PP
Internally, the kernel sets the
.I si_signo
field to the value specified in
.IR sig ,
so that the receiver of the signal can also obtain
the signal number via that field.
.PP
The
.BR rt_tgsigqueueinfo ()
system call is like
.BR rt_sigqueueinfo (),
but sends the signal and data to the single thread
specified by the combination of
.IR tgid ,
a thread group ID,
and
.IR tid ,
a thread in that thread group.
.SH RETURN VALUE
On success, these system calls return 0.
On error, they return \-1 and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EAGAIN
The limit of signals which may be queued has been reached.
(See
.BR signal (7)
for further information.)
.TP
.B EINVAL
.IR sig ,
.IR tgid ,
or
.IR tid
was invalid.
.TP
.B EPERM
The caller does not have permission to send the signal to the target.
For the required permissions, see
.BR kill (2).
Or:
.I uinfo->si_code
is invalid.
.TP
.B ESRCH
.BR rt_sigqueueinfo ():
No thread group matching
.I tgid
was found.
.PP
.BR rt_tgsigqueinfo ():
No thread matching
.I tgid
and
.I tid
was found.
.SH VERSIONS
The
.BR rt_sigqueueinfo ()
system call was added to Linux in version 2.2.
The
.BR rt_tgsigqueueinfo ()
system call was added to Linux in version 2.6.31.
.SH CONFORMING TO
These system calls are Linux-specific.
.SH NOTES
Since these system calls are not intended for application use,
there are no glibc wrapper functions; use
.BR syscall (2)
in the unlikely case that you want to call them directly.
.PP
As with
.BR kill (2),
the null signal (0) can be used to check if the specified process
or thread exists.
.SH SEE ALSO
.BR kill (2),
.BR sigaction (2),
.BR sigprocmask (2),
.BR tgkill (2),
.BR pthread_sigqueue (3),
.BR sigqueue (3),
.BR signal (7)
.SH COLOPHON
This page is part of release 4.15 of the Linux
.I 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/.
