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Re: Threads

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

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?

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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