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RE: Problem in pthread_cancel() ?
- To: 'Ollie Leahy' <ollie at mpt dot ie>, pthreads-win32 at sources dot redhat dot com
- Subject: RE: Problem in pthread_cancel() ?
- From: "Bossom, John" <John dot Bossom at Cognos dot COM>
- Date: Wed, 6 Sep 2000 11:21:26 -0400
I believe the original implementation would create an instance
of a pthread struct for you... (and it should) thus allowing
you to use pthread calls against your current "thread" of execution
such as the main process (note: the "process" is simply the
initial thread). This would eliminate the need to create
an explicit pthread in order to do these kind of pthread calls
The mechanism I would recommend is "pthread_self" should boot-strap
an instance of the pthread struct to the current thread of execution
if you are not within a thread explicitly created with pthread_create.
I don't know how the current implementation is getting "self" (I assume
it is from thread-specific memory) however, I recommend that "self"
be retrieved using pthread_self(). My original implementation DID
bind an instance of the pthread struct the calling thread if not
explicitly created with pthread
-----Original Message-----
From: Ollie Leahy [mailto:ollie@mpt.ie]
Sent: Wednesday, September 06, 2000 4:33 AM
To: pthreads-win32@sources.redhat.com
Subject: Problem in pthread_cancel() ?
I don't know whether I am mis-using pthreads or if
there is a problem in the pthreads-win32 implementation.
When my process is closing down I want all pthreads
to complete before I finally return from the process.
To do this I send a pthread_cancel() to those threads
that are blocking (on an accept() or a recv() call)
on Linux this works but with pthread-win32 if I call
pthread_cancel() from the main process the process
core dumps. If I create a thread and call cancel()
from the thread then everything works fine.
I had a quick look at the code for pthread_cancel() and
the problem seems to be that pthread_cancel() tests
whether it is being called to cancel the calling thread
and references the variable 'self'. But since I call the
function from the process and not from a thread self
is NULL, so as soon as self is dereferenced the process
crashes.
I have fixed my problem by creating a thread to call
cancel, and I've also hacked the pthread-win32 code
so that if self is NULL pthread_cancel() does not
try to defreference it. I would like to know whether
I'm trying to do something illegal as far as pthreads
are concerned or whether there is a bug in the win32
implementation.
Regards,
Ollie