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

From: Ingo Molnar
Date: Sat Apr 28 2018 - 03:15:50 EST

* Ingo Molnar <mingo@xxxxxxxxxx> 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.