On Mon, 3 Mar 2003, Jon Nelson wrote:
> On Fri, 28 Feb 2003, Christian Reis wrote:
>
> > On Fri, Feb 28, 2003 at 08:56:04AM -0600, Jon Nelson wrote:
> > > To make progress bars work, I use the following code:
> > >
> > > while gtk.events_pending():
> > > gtk.mainiteration(0)
> > >
> > > And here is where I get into trouble.
> > >
> > > Assume the FIFO is still readable (perhaps I haven't read all of the
> > > data, or perhaps new data has arrived).
> > >
> > > It appears that gtk.mainiteration will call read_from_fifo *again*,
> > > which calls handle_fifo, which may result in calling mainiteration,
> > > which may result in read_from_fifo being called, which ....
> >
> > Why not just use a global variable to lock this? Something like
> >
> > self.block_read = 1
> >
> > and then set this just before your mainiteration loop. Then check for it
> > inside read_from_fifo and only perform the actual read if you aren't
> > blocked.
>
> I tried that very approach, and it didn't work for me. I didn't spend a
> great deal of time trying to figure out why. I'll look into it.
Tried it. Doesn't work. Here's why.
Assume code similar to this:
def read_from_fifo(self, file, condition):
self.log("in read_from_fifo - %s" % (str((file,condition))))
if self.block_read:
return file
...
self.io_queue.put( (verb, args) )
self.block_read = 1
self.handle_fifo_here()
self.block_read = 0
return file
Every time mainiteration gets called, it appears that read_from_fifo
gets called again. It does nothing, and returns file (success).
It simply keeps getting called over and over and over again. Why?
I tossed a simple print statement inside the while gtk.events_pending()
loop, and yep. They are forever pending.
I'll try another approach: the above combined with returning none, to
disable the reading from the fifo, and then re-enable the I/O monitoring
after enabling the block:
def read_from_fifo(self, file, condition):
self.log("in read_from_fifo - %s" % (str((file,condition))))
if self.block_read:
return gtk.FALSE # disables the I/O monitoring
...
self.io_queue.put( (verb, args) )
self.block_read = 1
self.handle_fifo_here()
self.block_read = 0
self.enable_fifo_read() # <- or whatever it will be called.
return file
==== Experiment =====
Nope. That doesn't work either. While there are no longer events
pending, the process still hangs. An strace shows that it appears to be
locked:
gettimeofday({1046702234, 903693}, NULL) = 0
rt_sigprocmask(SIG_SETMASK, NULL, [RTMIN], 8) = 0
rt_sigsuspend([]
...
Still, I'm open to ideas!
--
"Never try to write to ROM - it wastes your time and annoys the ROM."
Jon Nelson <[EMAIL PROTECTED]>
C and Python Code Gardener
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