UTRACE_SET_EVENTS(9) utrace core API UTRACE_SET_EVENTS(9)NAME
utrace_set_events - choose which event reports a tracing engine gets
SYNOPSIS
int utrace_set_events(struct task_struct * target, struct utrace_engine * engine, unsigned long events);
ARGUMENTS
target
thread to affect
engine
attached engine to affect
events
new event mask
DESCRIPTION
This changes the set of events for which engine wants callbacks made.
This fails with -EALREADY and does nothing if you try to clear UTRACE_EVENT(DEATH) when the report_death callback may already have begun,
if you try to clear UTRACE_EVENT(REAP) when the report_reap callback may already have begun, or if you try to newly set UTRACE_EVENT(DEATH)
or UTRACE_EVENT(QUIESCE) when target is already dead or dying.
This can fail with -ESRCH when target has already been detached, including forcible detach on reaping.
If target was stopped before the call, then after a successful call, no event callbacks not requested in events will be made; if
UTRACE_EVENT(QUIESCE) is included in events, then a report_quiesce callback will be made when target resumes.
If target was not stopped and events excludes some bits that were set before, this can return -EINPROGRESS to indicate that target may have
been making some callback to engine. When this returns zero, you can be sure that no event callbacks you've disabled in events can be made.
If events only sets new bits that were not set before on engine, then -EINPROGRESS will never be returned.
To synchronize after an -EINPROGRESS return, see utrace_barrier.
When target is current, -EINPROGRESS is not returned. But note that a newly-created engine will not receive any callbacks related to an
event notification already in progress. This call enables events callbacks to be made as soon as engine becomes eligible for any callbacks,
see utrace_attach_task.
These rules provide for coherent synchronization based on UTRACE_STOP, even when SIGKILL is breaking its normal simple rules.
Kernel Hackers Manual 2.6. July 2010 UTRACE_SET_EVENTS(9)
Check Out this Related Man Page
Tcl_DoOneEvent(3) Tcl Library Procedures Tcl_DoOneEvent(3)__________________________________________________________________________________________________________________________________________________NAME
Tcl_DoOneEvent - wait for events and invoke event handlers
SYNOPSIS
#include <tcl.h>
int
Tcl_DoOneEvent(flags)
ARGUMENTS
int flags (in) This parameter is normally zero. It may be an OR-ed combination of any of the following flag bits: TCL_WIN-
DOW_EVENTS, TCL_FILE_EVENTS, TCL_TIMER_EVENTS, TCL_IDLE_EVENTS, TCL_ALL_EVENTS, or TCL_DONT_WAIT.
_________________________________________________________________DESCRIPTION
This procedure is the entry point to Tcl's event loop; it is responsible for waiting for events and dispatching event handlers created with
procedures such as Tk_CreateEventHandler, Tcl_CreateFileHandler, Tcl_CreateTimerHandler, and Tcl_DoWhenIdle. Tcl_DoOneEvent checks to see
if events are already present on the Tcl event queue; if so, it calls the handler(s) for the first (oldest) event, removes it from the
queue, and returns. If there are no events ready to be handled, then Tcl_DoOneEvent checks for new events from all possible sources. If
any are found, it puts all of them on Tcl's event queue, calls handlers for the first event on the queue, and returns. If no events are
found, Tcl_DoOneEvent checks for Tcl_DoWhenIdle callbacks; if any are found, it invokes all of them and returns. Finally, if no events or
idle callbacks have been found, then Tcl_DoOneEvent sleeps until an event occurs; then it adds any new events to the Tcl event queue, calls
handlers for the first event, and returns. The normal return value is 1 to signify that some event was processed (see below for other
alternatives).
If the flags argument to Tcl_DoOneEvent is non-zero, it restricts the kinds of events that will be processed by Tcl_DoOneEvent. Flags may
be an OR-ed combination of any of the following bits:
TCL_WINDOW_EVENTS - Process window system events.
TCL_FILE_EVENTS - Process file events.
TCL_TIMER_EVENTS - Process timer events.
TCL_IDLE_EVENTS - Process idle callbacks.
TCL_ALL_EVENTS - Process all kinds of events: equivalent to OR-ing together all of the above flags or specifying none of them.
TCL_DONT_WAIT - Do not sleep: process only events that are ready at the time of the call.
If any of the flags TCL_WINDOW_EVENTS, TCL_FILE_EVENTS, TCL_TIMER_EVENTS, or TCL_IDLE_EVENTS is set, then the only events that will be con-
sidered are those for which flags are set. Setting none of these flags is equivalent to the value TCL_ALL_EVENTS, which causes all event
types to be processed. If an application has defined additional event sources with Tcl_CreateEventSource, then additional flag values may
also be valid, depending on those event sources.
The TCL_DONT_WAIT flag causes Tcl_DoOneEvent not to put the process to sleep: it will check for events but if none are found then it
returns immediately with a return value of 0 to indicate that no work was done. Tcl_DoOneEvent will also return 0 without doing anything
if the only alternative is to block forever (this can happen, for example, if flags is TCL_IDLE_EVENTS and there are no Tcl_DoWhenIdle
callbacks pending, or if no event handlers or timer handlers exist).
Tcl_DoOneEvent may be invoked recursively. For example, it is possible to invoke Tcl_DoOneEvent recursively from a handler called by
Tcl_DoOneEvent. This sort of operation is useful in some modal situations, such as when a notification dialog has been popped up and an
application wishes to wait for the user to click a button in the dialog before doing anything else.
KEYWORDS
callback, event, handler, idle, timer
Tcl 7.5 Tcl_DoOneEvent(3)