From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: Andrea Parri <andrea.parri@amarulasolutions.com>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
Alan Stern <stern@rowland.harvard.edu>,
Will Deacon <will.deacon@arm.com>,
Boqun Feng <boqun.feng@gmail.com>,
Nicholas Piggin <npiggin@gmail.com>,
David Howells <dhowells@redhat.com>,
Jade Alglave <j.alglave@ucl.ac.uk>,
Luc Maranget <luc.maranget@inria.fr>,
Akira Yokosawa <akiyks@gmail.com>,
Daniel Lustig <dlustig@nvidia.com>
Subject: Re: [RFC PATCH] tools/memory-model: Remove (dep ; rfi) from ppo
Date: Tue, 26 Feb 2019 11:45:51 +0100 [thread overview]
Message-ID: <20190226104551.GF32534@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190226093009.GS32477@hirez.programming.kicks-ass.net>
On Tue, Feb 26, 2019 at 10:30:09AM +0100, Peter Zijlstra wrote:
> On Mon, Feb 25, 2019 at 09:55:17AM -0800, Paul E. McKenney wrote:
> > But if you know of any code in the Linux kernel that needs to compare
> > pointers, one of which might be in the process of being freed, please
> > do point me at it.
>
> I'm having the utmost difficulty of understanding why that would be a
> problem. It's just a value. Freeing memory does not affect the actual
> memory or any pointers to it.
>
> *confusion*
>
> None of this makes any kind of sense.
I found and started to read:
www.open-std.org/jtc1/sc22/wg14/www/docs/n2311.pdf
and that's all massive bong-hits. That's utterly insane.
Even the proposed semantics are crazy; they include UB and are therefore
broken on principle. But also; the provenance ID has words like:
"allocated storage duration", how is that well defined in the context of
concurrent execution?
Also, isn't the kernel filled with inter-object pointer arithmetic?
PNVI also looks like something that simply cannot work; how are we at
compile time supposed to know the active (concurrent modified) heap
layout. What is a 'live' object?
next prev parent reply other threads:[~2019-02-26 10:45 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-19 22:57 [RFC PATCH] tools/memory-model: Remove (dep ; rfi) from ppo Andrea Parri
2019-02-19 22:57 ` Andrea Parri
2019-02-20 2:01 ` Paul E. McKenney
2019-02-20 2:01 ` Paul E. McKenney
2019-02-20 9:26 ` Peter Zijlstra
2019-02-20 9:26 ` Peter Zijlstra
2019-02-20 9:57 ` Will Deacon
2019-02-20 9:57 ` Will Deacon
2019-02-20 13:17 ` Andrea Parri
2019-02-20 13:17 ` Andrea Parri
2019-02-20 13:14 ` Andrea Parri
2019-02-20 13:14 ` Andrea Parri
2019-02-20 13:27 ` Peter Zijlstra
2019-02-20 13:27 ` Peter Zijlstra
2019-02-22 11:21 ` Andrea Parri
2019-02-22 11:21 ` Andrea Parri
2019-02-22 13:00 ` Peter Zijlstra
2019-02-22 13:00 ` Peter Zijlstra
2019-02-25 17:55 ` Paul E. McKenney
2019-02-25 17:55 ` Paul E. McKenney
2019-02-26 9:21 ` Peter Zijlstra
2019-02-26 9:21 ` Peter Zijlstra
2019-02-26 9:30 ` Peter Zijlstra
2019-02-26 9:30 ` Peter Zijlstra
2019-02-26 10:45 ` Peter Zijlstra [this message]
2019-02-26 10:45 ` Peter Zijlstra
2019-02-26 11:21 ` Peter Zijlstra
2019-02-26 11:21 ` Peter Zijlstra
2019-02-26 11:25 ` Peter Zijlstra
2019-02-26 11:25 ` Peter Zijlstra
2019-02-26 11:30 ` Peter Zijlstra
2019-02-26 11:30 ` Peter Zijlstra
2019-02-26 11:38 ` Borislav Petkov
2019-02-26 11:38 ` Borislav Petkov
2019-02-26 13:49 ` Peter Zijlstra
2019-02-26 13:49 ` Peter Zijlstra
2019-02-26 14:28 ` Paul E. McKenney
2019-02-26 14:28 ` Paul E. McKenney
2019-02-26 14:47 ` Peter Zijlstra
2019-02-26 14:47 ` Peter Zijlstra
2019-02-26 15:39 ` Paul E. McKenney
2019-02-26 15:39 ` Paul E. McKenney
2019-02-26 14:56 ` Akira Yokosawa
2019-02-26 14:56 ` Akira Yokosawa
2019-02-26 15:04 ` Paul E. McKenney
2019-02-26 15:04 ` Paul E. McKenney
2019-02-26 15:09 ` Akira Yokosawa
2019-02-26 15:09 ` Akira Yokosawa
2019-02-26 15:04 ` Peter Zijlstra
2019-02-26 15:04 ` Peter Zijlstra
2019-03-06 15:46 ` Akira Yokosawa
2019-03-06 15:46 ` Akira Yokosawa
2019-03-06 16:58 ` Peter Zijlstra
2019-03-06 16:58 ` Peter Zijlstra
2019-03-06 17:26 ` Paul E. McKenney
2019-03-06 17:26 ` Paul E. McKenney
2019-03-06 17:24 ` Paul E. McKenney
2019-03-06 17:24 ` Paul E. McKenney
2019-03-02 15:27 ` Akira Yokosawa
2019-03-02 15:27 ` Akira Yokosawa
2019-03-04 16:09 ` Paul E. McKenney
2019-03-04 16:09 ` Paul E. McKenney
2019-02-20 13:41 ` Will Deacon
2019-02-20 13:41 ` Will Deacon
2019-02-20 15:30 ` Alan Stern
2019-02-20 15:30 ` Alan Stern
2019-02-20 15:22 ` Alan Stern
2019-02-20 15:22 ` Alan Stern
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