linux-kernel - Re: [PATCH 0/9] [v3] x86, pkeys: two protection keys bug fixes

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Date:   Sat, 28 Apr 2018 09:15:38 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linuxram@...ibm.com, tglx@...utronix.de, dave.hansen@...el.com,
        mpe@...erman.id.au, akpm@...ux-foundation.org, shuah@...nel.org,
        shakeelb@...gle.com
Subject: Re: [PATCH 0/9] [v3] x86, pkeys: two protection keys bug fixes

* Ingo Molnar <mingo@...nel.org> wrote:

> After I got the GDB backtraces I tried to clean up leftover tasks, but the main 
> thread would not go away:
> 
>  4006 pts/0    00:00:00 protection_keys <defunct>
> 
> neither SIGCONT nor SIGKILL appears to help:

Just seconds after I sent this I found out that this was user error: I forgot 
about a gdb session I still had running, which understandably blocked the task 
from being cleaned up. Once I exited GDB it all got cleaned up properly.

The hang problem is still there, if I run a script like this:

 while :; do date; echo -n "32-bit: "; ./protection_keys_32 >/dev/null; date; echo -n "64-bit: "; ./protection_keys_64 >/dev/null; done

then within a minute one of the testcases hangs reliably.

Out of 4 attempts so far one hang was in the 32-bit testcase, 3 hangs were in the 
64-bit testcase - so 64-bit appears to trigger it more frequently.

Thanks,

	Ingo