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       rt_sigqueueinfo, rt_tgsigqueueinfo - queue a signal and data


       int rt_sigqueueinfo(pid_t tgid, int sig, siginfo_t *info);

       int rt_tgsigqueueinfo(pid_t tgid, pid_t tid, int sig,
                             siginfo_t *info);

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


       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 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 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.

              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.


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


       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 found.

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


       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.


       These system calls are Linux-specific.


       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.


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


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