linux-kernel - Re: [PATCH] x86, traps: Fix ist

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Date:	Sat, 31 Jan 2015 10:09:03 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Andy Lutomirski <luto@...capital.net>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>
CC:	Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Tony Luck <tony.luck@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Josh Triplett <josh@...htriplett.org>,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH] x86, traps: Fix ist_enter from userspace

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@...cle.com>
> Signed-off-by: Andy Lutomirski <luto@...capital.net>

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

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


Thanks,
Sasha
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