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