.\" Copyright (c) 2002 Michael Kerrisk .\" .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. .\" .\" Formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" .\" added note on self-signalling, aeb, 2002-06-07 .\" .TH RT_SIGQUEUEINFO 2 2003-04-07 "Linux 2.4.19" "Linux Programmer's Manual" .SH NAME rt_sigqueueinfo \- queue a signal and data to a process .SH SYNOPSIS .BI "long sys_rt_sigqueueinfo(int " pid ", int " sig ", siginfo_t * " uinfo "); .SH DESCRIPTION .BR sys_rt_sigqueueinfo () sends the signal specified in .I sig to the process whose PID is given in .IR pid . The null signal (0) can be used to check if a process with a given PID exists. .PP The .I uinfo argument is used to specify an accompanying item of data (either an integer or a pointer value) in the sigval part of the siginfo_t structure to be sent with the signal. If the receiving process has installed a handler for this signal using the .B SA_SIGINFO flag to .BR sigaction (2), then it can obtain this data via the .I si_value field of the .I siginfo_t structure passed as the second argument to the handler. Furthermore, the .I si_code field of that structure will be set to .BR SI_QUEUE . .SH "RETURN VALUE" On success, .BR sys_rt_sigqueueinfo () returns 0, indicating that the signal was successfully queued to the receiving proces. Otherwise, one of the following errors is returned. .SH ERRORS .TP .B -EAGAIN The limit of signals which may be queued has been reached. .TP .B -EINVAL .I sig was invalid. .TP .B -ESRCH No process has a PID matching .IR pid . .TP .B -EPERM The process does not have permission to send the signal to the receiving process. .TP .B -EFAULT memory error. .SH NOTES If this function results in the sending of a signal to the process that invoked it, and that signal was not blocked by the calling thread, and no other threads were willing to handle this signal (either by having it unblocked, or by waiting for it using .BR sigwait (3)), then at least some signal must be delivered to this thread before this function returns. .SH "CONFORMING TO" POSIX 1003.1-2001 .SH "SEE ALSO" .BR kill (2), .BR sigaction (2), .BR signal (2), .BR sigwait (3), .BR signal (7), .BR sigqueue (2) .\" Copyright (c) 2002, 2011 Michael Kerrisk .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" .TH rt_sigqueueinfo 2 2023-03-30 "Linux man-pages 6.04" .SH NAME rt_sigqueueinfo, rt_tgsigqueueinfo \- queue a signal and data .SH LIBRARY Standard C library .RI ( libc ", " \-lc ) .SH SYNOPSIS .nf .BR "#include " " /* Definition of " SI_* " constants */" .BR "#include " " /* Definition of " SYS_* " constants */" .B #include .PP .BI "int syscall(SYS_rt_sigqueueinfo, pid_t " tgid , .BI " int " sig ", siginfo_t *" info ); .BI "int syscall(SYS_rt_tgsigqueueinfo, pid_t " tgid ", pid_t " tid , .BI " int " sig ", siginfo_t *" info ); .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 info 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 ). The caller should set the following fields in this structure: .TP .I si_code This should be one of the .B SI_* codes in the Linux kernel source file .IR include/asm\-generic/siginfo.h . If the signal is being sent to any process other than the caller itself, the following restrictions apply: .RS .IP \[bu] 3 The code can't be a value greater than or equal to zero. In particular, it can't be .BR SI_USER , which is used by the kernel to indicate a signal sent by .BR kill (2), and nor can it be .BR SI_KERNEL , which is used to indicate a signal generated by the kernel. .IP \[bu] The code can't (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). .RE .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 .I 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). .TP .B EPERM .I tgid specifies a process other than the caller and .I info\->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 STANDARDS Linux. .SH HISTORY .TP .BR rt_sigqueueinfo () Linux 2.2. .TP .BR rt_tgsigqueueinfo () Linux 2.6.31. .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 pidfd_send_signal (2), .BR sigaction (2), .BR sigprocmask (2), .BR tgkill (2), .BR pthread_sigqueue (3), .BR sigqueue (3), .BR signal (7)