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Subject: Re: [GIT PULL] Please pull proc and exec work for 5.7-rc1
To:     Linus Torvalds <torvalds@linux-foundation.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     Waiman Long <longman@redhat.com>, Ingo Molnar <mingo@kernel.org>,
        Will Deacon <will@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Alexey Gladkov <gladkov.alexey@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>
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From:   Bernd Edlinger <bernd.edlinger@hotmail.de>
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On 4/9/20 11:17 PM, Linus Torvalds wrote:
> On Thu, Apr 9, 2020 at 2:03 PM Eric W. Biederman <ebiederm@xmission.com> wrote:
>>
>> But no.  While you are goind a good job at spotting odd corner
>> cases that need to be fixed.  This also is not the cause of the
>> deadlock.  It is nothing that subtle.
> 
> So Eric, I'm now going to stop wasting my time on arguing with you.
> 
> Since both you and Bernd claimed to be too busy to even bother testing
> that thing, I just built it and booted it.
> 
> And guess what? That thing makes your non-deadlock thing go away.
> 
> So it's _literally_ that simple.
> 

You known I was right from the beginning :-) :-) (-: (-:,
I said you would have to adjust the test.  I only thought of the
second part, so that is were I was wrong.

Yeah Thanks.  My real problem is called OpenSSL 3.0 + FIPS and it feels
like a very big pain in the ass......

But please tell nobody.  That is a secret :-)


Thanks
Bernd.

> Now, does it make the tests "pass"? No.
> 
> Because the "vmaccess" test fails because the open() now fails -
> because we simply don't wait for that dead thread any more, so the
> /proc/<pid>/mem thing doesn't exist.
> 
> And for the same reason that "attach" test now no longer returns
> EAGAIN, it just attaches to the remaining execlp thing instead.
> 
> So I'm not just good at "spotting odd corner cases". I told you why
> that bogus deadlock of yours failed - the execve was pointlessly
> waiting for a dead thread that had marked itself ptraced, and nobody
> was reaping it.
> 
> And it appears you were too lazy to even try it out.
> 
> Yes, that whole "notify_dead" count vs "tsk->exit_state" test is
> fundamentally racy. But that race happens to be irrelevant for the
> test case in question.
> 
> So until you can actually add something to the discussion, I'm done
> with this thread.
> 
>            Linus
>