rt_sigqueueinfo, rt_tgsigqueueinfo - queue a signal and data
Standard C library (
libc,
-lc)
#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 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:
- si_code
- 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.
- 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.
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 in Linux 2.2. The
rt_tgsigqueueinfo() system call was added in Linux 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)