Re: [libmicrohttpd] MHD_handle_connection race leads to deadlock in MHD_stop_daemon

[Christian Grothoff]

On Wednesday 14 October 2009 15:13:02 Mike Crowe wrote:
> I temporarily hacked around the problem by employing a similar
> fix. It's not ideal, as you say, but it does work. I'm in favour of
> it, at least in the short term.
> 
> I did wonder whether it would be possible to use pthread_cancel and
> disable cancellation around calls to the callbacks but it would
> require a bit of work to ensure that the necessary cleanup occurred.

pthread_cancel is horrible and even without its inherent problems, given that 
we have callbacks into arbitrary code (MHD-response!) we can not use it.
 
> It would appear that pselect is designed to solve this problem. I
> might try using it if it is available and fall back to your fix if
> not. Some care might be required if the code is relying on SIGALRM waking
> up reads and writes as well as the select.

pselect was designed to solve the problem, but pselect is not as portable 
*and* on some systems (glibc!) the specific implementation of pselect still has 
the same problem (see select man page).  So I don't think pselect is a 
worthwile direction to go into.

Best,

Christian
-- 
http://grothoff.org/christian/