Subj : Re: pthread_cancel
To   : comp.programming.threads
From : Giancarlo Niccolai
Date : Mon May 09 2005 12:55 pm

doug wrote:

> "Greg Law" <law@privacy.net> wrote in message
> news:2l81pnF9h89tU1@uni-berlin.de...
>> Hi,
>>
>> I am calling pthread_cancel on a thread that has canceling enabled, of
>> deferred type.  The thread I am canceling never makes any calls to
>> testcancel, or waits on any condition variables.  So it surprises me that
>> the cancelation has any effect at all.  That is, in the following program
>> the thread I've created is terminated (to my surprise).  I guess I've not
>> understood correctly when threads may be canceled?
>>
>> Cheers,
>>
>> Greg
>>

> 
> If I remember correctly, I think POSIX states that certain system calls
> (read, write, etc.) are cancellation points.  So the printf() in your
> Start() routine would be a cancellation point.
> What version of OS & threading lib are you using?  I know that until
> recently, LinuxThreads hand't actually implemented this, though (e.g. see
> manpage for pthread_cancel on an older Fedora Core 3 system).  It may have
> been fixed recently, or may be correct in NPTL.

Correct; printf may or may not be a cancellation point depending on the fact
that it calls or calls not write() to perform an output to a stream. I
don't have news about printf being explicitly declared NOT a cancellation
point by posix, so, what happens inside printf is to be considered
"random".

Giancarlo.

.