06-18-2008
shared memory read/write using threads
I am looking for C program source code. Could you please help me in finding the source code required mentioned below.
program to create multiple threads (one master thread and rest worker threads) and using the threads write into and read from shared memory
Restrictions:
Only one thread should be able to read at any instant of time into shared memory region.
Only one thread should be able to write at any instant of time into shared memory region.
Worker threads should inform the master thread after every read and write operation.
Master thread inform the worker thread (which is waiting to acquire shared memory region) that read or write operation is successful and it can acquire the memory for either reading and writing operations.
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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)