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Message-ID:	<5448E6F9.8040005@dronecode.org.uk>
Date:	Thu, 23 Oct 2014 12:31:05 +0100
From:	Jon TURNEY <jon DOT turney AT dronecode DOT org DOT uk>
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To:	Ken Brown <kbrown AT cornell DOT edu>, cygwin AT cygwin DOT com
Subject:	Re: Threads
References:	<54450835 DOT 3050602 AT cornell DOT edu>
In-Reply-To:	<54450835.3050602@cornell.edu>

On 20/10/2014 14:03, Ken Brown wrote:
> Or is there some other plausible explanation for "impossible" crashes?
> This can't just be a result of a gdb bug, because in at least one case
> the assertion can be shown to be valid by using printf instead of gdb.
>
> [*] By "impossible" I mean that examination of the relevant variables in
> gdb shows that the assertions are in fact true.  Two ongoing examples are
>
>     http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18438
>     http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18769

As a suggestion, you might want to also take a careful look at how 
signal delivery is implemented in cygwin on x86_64

I had a vague idea that there was, at some time in the past, a fix made 
for register corruption on x86_64 after a signal was handled, but I 
can't find it now, so maybe I imagined it.  But if for e.g. the flags 
register was getting corrupted when a signal interrupts the main thread, 
that could perhaps also explain what is being seen.

(More generally, it doesn't have to be another thread which is causing 
these problems, it could be some form of interrupt)


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