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NAME

       stapprobes.signal - systemtap signal probe points

DESCRIPTION

       This  family  of  probe  points is used to probe signal activities.  It
       contains the following probe points:

       signal.send

              Fires when a signal is sent to a process

              Arguments:

              sig
                signal number

              sig_name
                a string representation of the signal

              sig_pid
                pid of the signal recipient process

              pid_name
                name of the signal recipient process

              si_code
                indicates the signal type

              task
                a task handle to the signal recipient

              sinfo
                the address of siginfo struct

              shared
                indicates whether this signal is shared by the thread group

              send2queue
                indicates whether this signal is sent to an existing sigqueue

              name
                name of the function used to send out this signal

       signal.send.return

              Fires when return from sending a signal

              Arguments:

              retstr
                the return value

                Return     values     for     "__group_send_sig_info"      and
              "specific_send_sig_info"

                     -  return  0  if  the  signal  is  sucessfully  sent to a
                     process, which means the following:

                     <1> the signal is ignored by receiving process

                     <2> this is a non-RT  signal  and  we  already  have  one
                     queued

                     <3> the signal is successfully added into the sigqueue of
                     receiving process

                     - return -EAGAIN if the sigqueue is overflow  the  signal
                     was RT and sent by user using something other than kill()

                Return values for "send_group_sigqueue"

                     - return 0 if the signal is either sucessfully added into
                     the  sigqueue of receiving process or a SI_TIMER entry is
                     already queued so just increment the overrun count

                     - return 1 if this signal is ignored by receiving process

                Return values for "send_sigqueue"

                     - return 0 if the signal is either sucessfully added into
                     the sigqueue of receiving process or a SI_TIMER entry  is
                     already queued so just increment the overrun count

                     - return 1 if this signal is ignored by receiving process

                     -  return  -1  if  the  task  is   marked   exiting,   so
                     posix_timer_event can redirect it to the group leader

              shared
                indicates whether this signal is shared by the thread group

              send2queue
                indicates whether this signal is sent to an existing sigqueue

              name
                name of the function used to send out this signal

       signal.checkperm

              Fires when check permissions for sending the signal

              Arguments:

              sig
                the number of the signal

              sig_name
                a string representation of the signal

              sig_pid
                pid of the signal recipient process

              pid_name
                name of the signal recipient process

              si_code
                indicates the signal type

              task
                a task handle to the signal recipient

              sinfo
                the address of siginfo struct

              name
                name of the probe point, is set to "signal.checkperm"

       signal.checkperm.return

              Fires when return from permissions check for sending a signal

              Arguments:

              retstr
                the return value

              name
                name of the probe point, is set to "signal.checkperm"

       signal.wakeup

              Fires when wake up the process for new active signals

              Arguments:

              sig_pid
                pid of the process to be woke up

              pid_name
                name of the process to be woke up

              resume
                indicate whether to wake up a task in STOPPED or TRACED state

              state_mask
                a  string representation indicate the mask of task states that
              can       be       woken.       Possible       values        are
              (TASK_INTERRUPTIBLE|TASK_STOPPED|TASK_TRACED)                and
              TASK_INTERRUPTIBLE.

       signal.check_ignored

              Fires when check whether the signal is ignored or not

              Arguments:

              sig_pid
                pid of the signal recipient process

              pid_name
                name of the signal recipient process

              sig
                the signal to be checked

              sig_name
                name of the signal

       signal.check_ignored.return

              Fires when return from signal.check_ignored

              Arguments:

              retstr
                return value. 0 indicate the current signal isn’t ignored.

       signal.force_segv

              Forces SIGSEGV when there are some issues while handling signals
              for the process

              Arguments:

              sig_pid
                pid of the signal recipient process

              pid_name
                name of the signal recipient process

              sig
                the signal being handled

              sig_name
                name of this signal

       signal.force_segv.return

              Fires when return from signal.force_segv

              Arguments:

              retstr
                return value. Always return 0

       signal.syskill

              Fires when sys_kill is called to send a signal to a process.

              Arguments:

              pid
                pid of the recipient process

              sig
                the signal to be sent

       signal.syskill.return

              Fires when returning from sys_kill

       signal.tgkill

              Fires when sys_tgkill is called to send a signal to one specific
              thread

              Arguments:

              pid
                pid of the recipient thread

              tgid
                thread group id which the target thread should have

              sig
                the signal to be sent

       signal.tgkill.return

              Fires when returning from sys_tgkill

       signal.tkill

              Fires when sys_tkill is called to send  a  signal  to  a  single
              process.

              Arguments:

              pid
                pid of the recipient process

              sig
                the signal to be sent

       signal.tkill.return

              Fires when returning from sys_tkill

       signal.send_sig_queue

              Fires when queue a signal to a process

              Arguments:

              sig
                the signal to be queued

              sig_name
                name of this signal

              sig_pid
                pid of the process to which the signal is queued

              pid_name
                name of the process  to which the signal is queued

              sigqueue_addr
                address of the signal queue

       signal.send_sig_queue.return

              Fires when return from signal.send_sig_queue

              Arguments:

              retstr
                return value

       signal.pending

              Fires  when  examine  the  set  of  signals that are pending for
              delivery to the calling thread

              Arguments:

              sigset_add
                address of user space sigset_t

              sigset_size
                sigset size

       signal.pending.return

              Fires when return from signal.pending

              Arguments:

              retstr
                return value

       signal.handle

              Fires when invoking the signal handler

              Arguments:

              sig
                signal number

              sig_name
                signal name

              sinfo
                address of siginfo struct

              sig_code
                the si_code of siginfo

              ka_addr
                Address of the k_sigaction struct associated with the signal

              oldset_addr
                Address of a bit mask array of blocked signals

              sig_mode
                indicates whether the signal is a User  Mode  or  Kernel  mode
              Signal

       signal.handle.return

              Fires when return from signal.handle

              Arguments:

              retstr
                return value of handle_signal()

       signal.do_action

              Fires by calling thread to examine and change a signal action

              Arguments:

              sig
                signal number

              sigact_addr
                address of the new sigaction struct associated with the signal

              oldsigact_addr
                address of a previous sigaction  struct  associated  with  the
              signal

              sa_handler
                the new handler of the signal

              sa_mask
                the new mask of the signal

       signal.do_action.return

              Fires when return from signal.do_action

              Arguments:

              retstr
                return value of do_sigaction()

       signal.procmask

              Fires by calling thread to examine and change blocked signals

              Arguments:

              how
                indicates how to change the blocked signals.
                Possible values are:
                  SIG_BLOCK=0 for blocking signals
                  SIG_UNBLOCK=1 for unblocking signals
                  SIG_SETMASK=2 for setting the signal mask

              sigset_addr
                address of sigset_t to be set

              oldsigset_addr
                address of the old sigset_t

              sigset
                the actual sigset to be set

       signal.procmask.return

              Fires when return from signal.procmask

              Arguments:

              retstr
                return value of sigprocmask()

       signal.flush

              Fires when flush all pending signals for a task

              Arguments:

              task
                the task handler of the process

              sig_pid
                pid of the task

              pid_name
                name of the task

SEE ALSO

       stap(1), stapprobes(5),