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select hangs forever...

From: Kenneth Haase <kh@beingmeta.com>
Date: Tue, 8 Jan 2002 08:58:45 -0500
Message-Id: <200201081715.g08HFMc22018@server1.beingmeta.com>
To: www-lib@w3.org
Cc: kh@beingmeta.com
Perhaps I'm using it wrong, but I have a problem where the select loop in 
HTEventList_loop hangs.  I am trying to use libwww, with its pseudo threads, 
from an external application which is actually threaded.  My approach is to 
run the libwww event loop in its own single thread; other threads create 
requests and then block until the libwww loop has finished processing it.  (I 
handle the locking with AFTER methods on the requests).

The problem is that when I start the loop, it enters a call to select with no 
file descriptors and no timeouts.  I then create a request which goes to the 
point where it need to get the actual connection; this can't happen right 
away, so the call just posts an event waiting for the socket to get its 
connection and continues.  However, because select is in its forever loop, it 
doesn't note that there is a new socket to be watched and the successful 
connection --- when it comes from the remote server --- is never recognized.

The fix I've come up with, appended below, is to replace the "never timeout" 
default case with a "look around every second" case.  Another approach, I 
suppose, would be to send a signal to the www thread, which will cause select 
to exit, but this seems messy and pretty non-portable.

Please let me know if this gets added to the official version, as I want to 
release the code which relies on it.  Alternatively, if there is a better way 
to get this same effect (adding a request after the main loop has been 
started from outside of the main loop), I would be delighted to hear about it.



Received on Tuesday, 8 January 2002 09:00:30 UTC

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