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Date: Sat, 31 Jan 2015 10:09:03 -0500
From: Sasha Levin <sasha.levin@oracle.com>
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To: Andy Lutomirski <luto@amacapital.net>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>
CC: Borislav Petkov <bp@alien8.de>, X86 ML <x86@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
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        Josh Triplett <josh@joshtriplett.org>,
        =?windows-1252?Q?Fr=E9d=E9ric_Weisbecker?= <fweisbec@gmail.com>
Subject: Re: [PATCH] x86, traps: Fix ist_enter from userspace
References: <54CC2FA8.7070006@oracle.com> <261ebee6aee55a4724746d0d7024697013c40a08.1422709102.git.luto@amacapital.net>
In-Reply-To: <261ebee6aee55a4724746d0d7024697013c40a08.1422709102.git.luto@amacapital.net>
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On 01/31/2015 08:01 AM, Andy Lutomirski wrote:
> context_tracking_user_exit() has no effect if in_interrupt() returns true,
> so ist_enter() didn't work.  Fix it by calling exception_enter(), and thus
> context_tracking_user_exit(), before incrementing the preempt count.
> 
> This also adds an assertion that will catch the problem reliably if
> CONFIG_PROVE_RCU=y to help prevent the bug from being reintroduced.
> 
> Fixes: 959274753857 x86, traps: Track entry into and exit from IST context
> Reported-by: Sasha Levin <sasha.levin@oracle.com>
> Signed-off-by: Andy Lutomirski <luto@amacapital.net>

I was running something like that overnight, looks like it fixes the problem.

	Tested-by: Sasha Levin <sasha.levin@oracle.com>


Thanks,
Sasha