From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: "Borislav Petkov" <bp@alien8.de>, "X86 ML" <x86@kernel.org>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Peter Zijlstra" <peterz@infradead.org>,
"Oleg Nesterov" <oleg@redhat.com>,
"Tony Luck" <tony.luck@intel.com>,
"Andi Kleen" <andi@firstfloor.org>,
"Josh Triplett" <josh@joshtriplett.org>,
"Frédéric Weisbecker" <fweisbec@gmail.com>
Subject: Re: [PATCH v4 2/5] x86, traps: Track entry into and exit from IST context
Date: Mon, 24 Nov 2014 14:57:54 -0800 [thread overview]
Message-ID: <20141124225754.GY5050@linux.vnet.ibm.com> (raw)
In-Reply-To: <CALCETrUA+z5z6bnOw63-EUiFD4WQtBXm1TE2DSRj3uG+d_k-bQ@mail.gmail.com>
On Mon, Nov 24, 2014 at 02:36:18PM -0800, Andy Lutomirski wrote:
> On Mon, Nov 24, 2014 at 2:34 PM, Paul E. McKenney
> <paulmck@linux.vnet.ibm.com> wrote:
> > On Mon, Nov 24, 2014 at 01:35:01PM -0800, Paul E. McKenney wrote:
[ . . . ]
> > And the following Promela model claims that your approach works.
> > Should I trust it? ;-)
> >
>
> I think so.
>
> Want to write a patch? If so, whose tree should it go in? I can add
> it to my IST series, but that seems a bit odd.
Working on it. ;-)
Thanx, Paul
> --Andy
>
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > /*
> > * Promela model for Andy Lutomirski's suggested change to rcu_nmi_enter()
> > * that allows nesting.
> > *
> > * This program is free software; you can redistribute it and/or modify
> > * it under the terms of the GNU General Public License as published by
> > * the Free Software Foundation; either version 2 of the License, or
> > * (at your option) any later version.
> > *
> > * This program is distributed in the hope that it will be useful,
> > * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > * GNU General Public License for more details.
> > *
> > * You should have received a copy of the GNU General Public License
> > * along with this program; if not, you can access it online at
> > * http://www.gnu.org/licenses/gpl-2.0.html.
> > *
> > * Copyright IBM Corporation, 2014
> > *
> > * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > */
> >
> > byte dynticks_nesting;
> > byte dynticks_nmi_nesting;
> > byte dynticks;
> > byte busy;
> >
> > /*
> > * Promela verision of rcu_nmi_enter().
> > */
> > inline rcu_nmi_enter()
> > {
> > assert(dynticks_nmi_nesting >= 0);
> > if
> > :: (dynticks & 1) == 0 ->
> > atomic {
> > dynticks = dynticks + 1;
> > }
> > assert((dynticks & 1) == 1);
> > dynticks_nmi_nesting = dynticks_nmi_nesting + 1;
> > assert(dynticks_nmi_nesting >= 1);
> > :: else ->
> > dynticks_nmi_nesting = dynticks_nmi_nesting + 2;
> > fi;
> > }
> >
> > /*
> > * Promela verision of rcu_nmi_exit().
> > */
> > inline rcu_nmi_exit()
> > {
> > assert(dynticks_nmi_nesting > 0);
> > assert((dynticks & 1) != 0);
> > if
> > :: dynticks_nmi_nesting != 1 ->
> > dynticks_nmi_nesting = dynticks_nmi_nesting - 2;
> > :: else ->
> > dynticks_nmi_nesting = 0;
> > atomic {
> > dynticks = dynticks + 1;
> > }
> > assert((dynticks & 1) == 0);
> > fi;
> > }
> >
> > /*
> > * Base-level NMI runs non-atomically. Crudely emulates process-level
> > * dynticks-idle entry/exit.
> > */
> > proctype base_NMI()
> > {
> > do
> > :: if
> > :: 1 -> atomic {
> > dynticks = dynticks + 1;
> > }
> > busy = 0;
> > :: 1 -> skip;
> > fi;
> > rcu_nmi_enter();
> > assert((dynticks & 1) == 1);
> > rcu_nmi_exit();
> > if
> > :: busy -> skip;
> > :: !busy ->
> > atomic {
> > dynticks = dynticks + 1;
> > }
> > busy = 1;
> > fi;
> > od;
> > }
> >
> > /*
> > * Nested NMI runs atomically to emulate interrupting base_level().
> > */
> > proctype nested_NMI()
> > {
> > do
> > :: atomic {
> > rcu_nmi_enter();
> > assert((dynticks & 1) == 1);
> > rcu_nmi_exit();
> > }
> > od;
> > }
> >
> > init {
> > dynticks_nesting = 0;
> > dynticks_nmi_nesting = 0;
> > dynticks = 0;
> > busy = 0;
> > run base_NMI();
> > run nested_NMI();
> > }
> >
>
>
>
> --
> Andy Lutomirski
> AMA Capital Management, LLC
>
next prev parent reply other threads:[~2014-11-24 22:58 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-21 21:26 [PATCH v4 0/5] x86: Rework IST interrupts Andy Lutomirski
2014-11-21 21:26 ` [PATCH v4 1/5] uprobes, x86: Fix _TIF_UPROBE vs _TIF_NOTIFY_RESUME Andy Lutomirski
2014-11-22 16:55 ` Borislav Petkov
2014-11-24 17:58 ` Andy Lutomirski
2014-11-21 21:26 ` [PATCH v4 2/5] x86, traps: Track entry into and exit from IST context Andy Lutomirski
2014-11-21 21:32 ` Andy Lutomirski
2014-11-21 22:07 ` Paul E. McKenney
2014-11-21 22:19 ` Andy Lutomirski
2014-11-21 22:55 ` Paul E. McKenney
2014-11-21 23:06 ` Andy Lutomirski
2014-11-21 23:38 ` Paul E. McKenney
2014-11-22 2:00 ` Andy Lutomirski
2014-11-22 4:20 ` Paul E. McKenney
2014-11-22 5:53 ` Andy Lutomirski
2014-11-22 23:41 ` Paul E. McKenney
2014-11-24 20:22 ` Andy Lutomirski
2014-11-24 20:54 ` Paul E. McKenney
2014-11-24 21:02 ` Andy Lutomirski
2014-11-24 21:35 ` Paul E. McKenney
2014-11-24 22:34 ` Paul E. McKenney
2014-11-24 22:36 ` Andy Lutomirski
2014-11-24 22:57 ` Paul E. McKenney [this message]
2014-11-24 23:31 ` Paul E. McKenney
2014-11-24 23:35 ` Andy Lutomirski
2014-11-24 23:50 ` Paul E. McKenney
2014-11-24 23:52 ` Andy Lutomirski
2014-11-25 18:58 ` Borislav Petkov
2014-11-25 19:16 ` Paul E. McKenney
2014-12-11 0:22 ` Tony Luck
2014-12-11 0:24 ` Andy Lutomirski
2015-01-05 21:46 ` Tony Luck
2015-01-05 21:54 ` Andy Lutomirski
2015-01-06 0:44 ` [PATCH] x86, mce: Get rid of TIF_MCE_NOTIFY and associated mce tricks Luck, Tony
2015-01-06 1:01 ` Andy Lutomirski
2015-01-06 18:00 ` Luck, Tony
2015-01-07 12:13 ` Borislav Petkov
2015-01-07 15:51 ` Andy Lutomirski
2015-01-07 15:58 ` Borislav Petkov
2015-01-07 16:12 ` Paul E. McKenney
2014-11-25 17:13 ` [PATCH v4 2/5] x86, traps: Track entry into and exit from IST context Paul E. McKenney
2014-11-27 7:03 ` Lai Jiangshan
2014-11-27 16:46 ` Paul E. McKenney
2014-11-24 21:27 ` Paul E. McKenney
2014-11-21 22:20 ` Frederic Weisbecker
2014-11-21 22:00 ` Paul E. McKenney
2014-11-22 17:20 ` Borislav Petkov
2014-11-24 19:48 ` Andy Lutomirski
2015-01-22 21:52 ` Sasha Levin
2015-01-23 17:58 ` Andy Lutomirski
2015-01-23 18:04 ` Borislav Petkov
2015-01-23 18:34 ` Andy Lutomirski
2015-01-23 20:48 ` Sasha Levin
2015-01-24 1:25 ` Andy Lutomirski
2015-01-28 16:33 ` Andy Lutomirski
2015-01-28 17:48 ` Paul E. McKenney
2015-01-28 21:02 ` Andy Lutomirski
2015-01-30 19:57 ` Sasha Levin
2015-01-31 1:28 ` Sasha Levin
2015-01-31 3:12 ` Andy Lutomirski
2015-01-31 12:50 ` Andy Lutomirski
2015-01-31 13:01 ` [PATCH] x86, traps: Fix ist_enter from userspace Andy Lutomirski
2015-01-31 15:09 ` Sasha Levin
2015-01-31 16:18 ` Paul E. McKenney
2015-02-01 2:17 ` Andy Lutomirski
2015-02-04 6:01 ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2014-11-21 21:26 ` [PATCH v4 3/5] x86, entry: Switch stacks on a paranoid entry " Andy Lutomirski
2014-11-24 15:55 ` Borislav Petkov
2014-11-21 21:26 ` [PATCH v4 4/5] x86: Clean up current_stack_pointer Andy Lutomirski
2014-11-24 11:39 ` Borislav Petkov
2014-11-21 21:26 ` [PATCH v4 5/5] x86, traps: Add ist_begin_non_atomic and ist_end_non_atomic Andy Lutomirski
2014-11-24 15:54 ` Borislav Petkov
2014-11-24 19:52 ` Andy Lutomirski
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