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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Peter Zijlstra <peterz@infradead.org>, Will Deacon <will.deacon@arm.com>
Cc: torvalds@linux-foundation.org, oleg@redhat.com,
	paulmck@linux.vnet.ibm.com, mpe@ellerman.id.au,
	npiggin@gmail.com, linux-kernel@vger.kernel.org,
	mingo@kernel.org, stern@rowland.harvard.edu,
	Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>
Subject: Re: [RFC][PATCH 1/5] mm: Rework {set,clear,mm}_tlb_flush_pending()
Date: Wed, 02 Aug 2017 10:17:41 +1000	[thread overview]
Message-ID: <1501633061.2792.137.camel@kernel.crashing.org> (raw)
In-Reply-To: <20170801164820.s46g2325kjjrymom@hirez.programming.kicks-ass.net>

On Tue, 2017-08-01 at 18:48 +0200, Peter Zijlstra wrote:
> On Tue, Aug 01, 2017 at 05:44:14PM +0100, Will Deacon wrote:
> > On Tue, Aug 01, 2017 at 06:39:03PM +0200, Peter Zijlstra wrote:
> > > Still this is all rather unsatisfactory. Either we should define
> > > flush_tlb*() to imply a barrier when its not a no-op (sparc64/ppc-hash)
> > > or simply make clear_tlb_flush_pending() an smp_store_release().
> > > 
> > > I prefer the latter option.
> > > 
> > > Opinions?
> > 
> > I prefer the latter option too, since I'd like to relax the arm64 TLB
> > flushing to have weaker barriers for the local case. Granted, that doesn't
> > break the NUMA migration code, but it would make the barrier semantics of
> > the TLB invalidation routines even more subtle if we were to define them
> > generally.
> 
> Another 'fun' question, is smp_mb() strong enough to order against the
> TLB invalidate? Because we really want to clear this flag _after_.
> 
> PowerPC for example uses PTESYNC before the TBLIE, so does a SYNC after
> work? Ben?

I have no idea. But then our tlbie has a ptesync after too no ? And
afaik a ptesync is a superset of sync.

Cheers,
Ben.

  parent reply	other threads:[~2017-08-02  1:01 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-07 16:15 [RFC][PATCH 0/5] Getting rid of smp_mb__before_spinlock Peter Zijlstra
2017-06-07 16:15 ` [RFC][PATCH 1/5] mm: Rework {set,clear,mm}_tlb_flush_pending() Peter Zijlstra
2017-06-09 14:45   ` Will Deacon
2017-06-09 18:42     ` Peter Zijlstra
2017-07-28 17:45     ` Peter Zijlstra
2017-08-01 10:31       ` Will Deacon
2017-08-01 12:02         ` Benjamin Herrenschmidt
2017-08-01 12:14           ` Peter Zijlstra
2017-08-01 16:39             ` Peter Zijlstra
2017-08-01 16:44               ` Will Deacon
2017-08-01 16:48                 ` Peter Zijlstra
2017-08-01 22:59                   ` Peter Zijlstra
2017-08-02  1:23                     ` Benjamin Herrenschmidt
2017-08-02  8:11                       ` Peter Zijlstra
2017-08-02  8:15                         ` Will Deacon
2017-08-02  8:43                           ` Will Deacon
2017-08-02  8:51                             ` Peter Zijlstra
2017-08-02  9:02                               ` Will Deacon
2017-08-02 22:54                                 ` Benjamin Herrenschmidt
2017-08-02  8:45                           ` Peter Zijlstra
2017-08-02  9:02                             ` Will Deacon
2017-08-02  9:18                               ` Peter Zijlstra
2017-08-02 13:57                         ` Benjamin Herrenschmidt
2017-08-02 15:46                           ` Peter Zijlstra
2017-08-02  0:17                   ` Benjamin Herrenschmidt [this message]
2017-08-01 22:42             ` Benjamin Herrenschmidt
2017-06-07 16:15 ` [RFC][PATCH 2/5] locking: Introduce smp_mb__after_spinlock() Peter Zijlstra
2017-06-07 16:15 ` [RFC][PATCH 3/5] overlayfs: Remove smp_mb__before_spinlock() usage Peter Zijlstra
2017-06-07 16:15 ` [RFC][PATCH 4/5] locking: Remove smp_mb__before_spinlock() Peter Zijlstra
2017-06-07 16:15 ` [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Peter Zijlstra
2017-06-08  0:32   ` Nicholas Piggin
2017-06-08  6:54     ` Peter Zijlstra
2017-06-08  7:29       ` Nicholas Piggin
2017-06-08  7:57         ` Peter Zijlstra
2017-06-08  8:21           ` Nicholas Piggin
2017-06-08  9:54           ` Michael Ellerman
2017-06-08 10:00             ` Nicholas Piggin
2017-06-08 12:45               ` Peter Zijlstra
2017-06-08 13:18                 ` Nicholas Piggin
2017-06-08 13:47                   ` Peter Zijlstra
2017-06-09 14:49 ` [RFC][PATCH 0/5] Getting rid of smp_mb__before_spinlock Will Deacon

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