rt_sigqueueinfo(2) — Linux manual page


rt_sigqueueinfo(2)         System Calls Manual        rt_sigqueueinfo(2)

NAME         top

       rt_sigqueueinfo, rt_tgsigqueueinfo - queue a signal and data

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <linux/signal.h>     /* Definition of SI_* constants */
       #include <sys/syscall.h>      /* Definition of SYS_* constants */
       #include <unistd.h>

       int syscall(SYS_rt_sigqueueinfo, pid_t tgid,
                   int sig, siginfo_t *info);
       int syscall(SYS_rt_tgsigqueueinfo, pid_t tgid, pid_t tid,
                   int sig, siginfo_t *info);

       Note: There are no glibc wrappers for these system calls; see

DESCRIPTION         top

       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

       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 info 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:

              This should be one of the SI_* codes in the Linux kernel
              source file include/asm-generic/siginfo.h.  If the signal
              is being sent to any process other than the caller itself,
              the following restrictions apply:

              •  The code can't be a value greater than or equal to
                 zero.  In particular, it can't be SI_USER, which is
                 used by the kernel to indicate a signal sent by
                 kill(2), and nor can it be SI_KERNEL, which is used to
                 indicate a signal generated by the kernel.

              •  The code can't (since Linux 2.6.39) be SI_TKILL, which
                 is used by the kernel to indicate a signal sent using

       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.

              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         top

       On success, these system calls return 0.  On error, they return
       -1 and errno is set to indicate the error.

ERRORS         top

       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).

       EPERM  tgid specifies a process other than the caller and
              info->si_code is invalid.

       ESRCH  rt_sigqueueinfo(): No thread group matching tgid was

       rt_tgsigqueinfo(): No thread matching tgid and tid was found.

STANDARDS         top


HISTORY         top

              Linux 2.2.

              Linux 2.6.31.

NOTES         top

       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         top

       kill(2), pidfd_send_signal(2), sigaction(2), sigprocmask(2),
       tgkill(2), pthread_sigqueue(3), sigqueue(3), signal(7)

Linux man-pages (unreleased)     (date)               rt_sigqueueinfo(2)

Pages that refer to this page: pidfd_send_signal(2)syscalls(2)tkill(2)pthread_sigqueue(3)sd_event_add_child(3)sigqueue(3)signal(7)system_data_types(7)