01-06-2011
Parent Thread Of Child Thread
Parent Thread Of Child Thread
Suppose a process creates some threads say threadC and threadD.
Later on each of these threads create new child threads say threadC1, threadC2, threadC3 etc. So a tree of threads will get created.
Is there any way to find out the parent thread of one such randomly created thread?
Actually when our application starts 70 threads gets created which is as per the requirement.
Later on as per the needs these 70 threads can create more threads.
So apart from these 70 threads a large number of other threads gets created(from these 70 threads) and destroyed randomly.
So imagine there is a tree of threads.
There is an issue coming up in one such randomly created thread.
On debugging the code we saw that the issue will be due to a value set by its
parent thread.
So we have to find the parent thread of this erroneus thread.
We are not able to get the parent thread id of this thread?
Will anybody let us know how to find the parent of such randomly created threads?
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LEARN ABOUT OSX
wx::thread
Wx::Thread(3) User Contributed Perl Documentation Wx::Thread(3)
NAME
Thread - using wxPerl with threads
SYNOPSIS
# the order of these use()s is important
use threads;
use threads::shared;
use Wx;
my $DONE_EVENT : shared = Wx::NewEventType;
my $worker = threads->create( &work );
# create frames, etc
my $frame = Wx::Frame->new( ... );
EVT_COMMAND( $frame, -1, $DONE_EVENT, &done );
$app->MainLoop;
sub done {
my( $frame, $event ) = @_;
print $event->GetData;
}
sub work {
# ... do stuff, create a shared $result value
my $threvent = new Wx::PlThreadEvent( -1, $DONE_EVENT, $result );
Wx::PostEvent( $frame, $threvent );
}
# event handler
sub OnCreateThread {
# @_ = () is necessary to avoid "Scalars leaked"
my( $self, $event ) = @_; @_ = ();
threads->create( ... );
}
DESCRIPTION
Threaded GUI application are somewhat different from non-GUI threaded applications in that the main thread (which runs the GUI) must never
block. Also, in wxWidgets, no thread other than the main thread can manipulate GUI objects. This leads to a hybrid model where worker
threads must send events to the main thread in order to change the GUI state or signal their termination.
Order of module loading
It's necessary for "use Wx" to happen after <use threads::shared>.
Sending events from worker threads
"Wx::PlThreadEvent" can be used to communicate between worker and GUI threads. The event can carry a shared value between threads.
my $DONE_EVENT : shared = Wx::NewEventType;
sub work {
# ... do some stuff
my $progress = new Wx::PlThreadEvent( -1, $DONE_EVENT, $progress );
Wx::PostEvent( $frame, $progress );
# ... do stuff, create a shared $result value
my $end = new Wx::PlThreadEvent( -1, $DONE_EVENT, $result );
Wx::PostEvent( $frame, $end );
}
The target of the event can be any "Wx::EvtHandler"
Receiving events from worker threads
"Wx::PlThreadEvent" is a command event and can be handled as such. The "->GetData" method can be used to retrieve the shared data
contained inside the event.
my $DONE_EVENT : shared = Wx::NewEventType;
EVT_COMMAND( $frame, -1, $DONE_EVENT, &done );
sub done {
my( $frame, $event ) = @_;
print $event->GetData;
}
Creating new threads
Creating new threads from event handlers works without problems except from a little snag. In order not to trigger a bug in the Perl
interpreter, all event handler that directly or indirectly cause a thread creation must clean @_ before starting the thread.
For example:
sub OnCreateThread {
my( $self, $event ) = @_; @_ = ();
threads->create( ... );
}
failure to do that will cause "scalars leaked" warnings from the Perl interpreter.
perl v5.10.0 2007-04-28 Wx::Thread(3)