Re: Threads

[Jon TURNEY <jon dot turney at dronecode dot org dot uk>]

On 23/10/2014 16:37, Corinna Vinschen wrote:
> On Oct 23 08:04, Ken Brown wrote:
> > On 10/23/2014 7:31 AM, Jon TURNEY wrote:
> > > 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.
> >
> > Is this what you're thinking of?
> >
> >    https://cygwin.com/ml/cygwin-cvs/2014-q1/msg00020.html
> >
> > > 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.
> >
> > Yes, flags register corruption is exactly what Eli suggested in the other
> > bug report I cited.
>
> The aforementioned patch was supposed to fix this problem and it is
> definitely in the current 1.7.32 release...

I didn't mean to suggest otherwise, just that perhaps a similar problem 
exists now.

So I made the attached test case to explore that.  Maybe I've made an 
obvious mistake with it, but on the face of it, it seems to demonstrate 
something...

jon@tambora /
$ gcc signal-stress.c  -Wall -O0 -g

jon@tambora /
$ ./a
failed: 2144210386 isn't equal to 2144210386, apparently

Note there is some odd load dependency. For me, it works fine when it's 
the only thing running, but when I start up something CPU intensive, it 
often fails...

Attachment: signal-stress.c
Description: Text document

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