From: Andrea Parri <andrea.parri@amarulasolutions.com>
To: Will Deacon <will.deacon@arm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>,
LKMM Maintainers -- Akira Yokosawa <akiyks@gmail.com>,
Boqun Feng <boqun.feng@gmail.com>,
David Howells <dhowells@redhat.com>,
Jade Alglave <j.alglave@ucl.ac.uk>,
Luc Maranget <luc.maranget@inria.fr>,
Nicholas Piggin <npiggin@gmail.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] tools/memory-model: Add write ordering by release-acquire and by locks
Date: Mon, 25 Jun 2018 10:19:20 +0200 [thread overview]
Message-ID: <20180625081920.GA5619@andrea> (raw)
In-Reply-To: <20180622183007.GD1802@arm.com>
On Fri, Jun 22, 2018 at 07:30:08PM +0100, Will Deacon wrote:
> > > I think the second example would preclude us using LDAPR for load-acquire,
> I don't think it's a moot point. We want new architectures to implement
> acquire/release efficiently, and it's not unlikely that they will have
> acquire loads that are similar in semantics to LDAPR. This patch prevents
> them from doing so,
By this same argument, you should not be a "big fan" of rfi-rel-acq in ppo ;)
consider, e.g., the two litmus tests below: what am I missing?
Andrea
C MP+fencewmbonceonce+pooncerelease-rfireleaseacquire-poacquireonce
{}
P0(int *x, int *y)
{
WRITE_ONCE(*x, 1);
smp_wmb();
WRITE_ONCE(*y, 1);
}
P1(int *x, int *y, int *z)
{
r0 = READ_ONCE(*y);
smp_store_release(z, 1);
r1 = smp_load_acquire(z);
r2 = READ_ONCE(*x);
}
exists (1:r0=1 /\ 1:r1=1 /\ 1:r2=0)
AArch64 MP+dmb.st+popl-rfilq-poqp
"DMB.STdWW Rfe PodRWPL RfiLQ PodRRQP Fre"
Generator=diyone7 (version 7.49+02(dev))
Prefetch=0:x=F,0:y=W,1:y=F,1:x=T
Com=Rf Fr
Orig=DMB.STdWW Rfe PodRWPL RfiLQ PodRRQP Fre
{
0:X1=x; 0:X3=y;
1:X1=y; 1:X3=z; 1:X6=x;
}
P0 | P1 ;
MOV W0,#1 | LDR W0,[X1] ;
STR W0,[X1] | MOV W2,#1 ;
DMB ST | STLR W2,[X3] ;
MOV W2,#1 | LDAPR W4,[X3] ;
STR W2,[X3] | LDR W5,[X6] ;
exists
(1:X0=1 /\ 1:X4=1 /\ 1:X5=0)
next prev parent reply other threads:[~2018-06-25 8:19 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-21 17:27 [PATCH 2/2] tools/memory-model: Add write ordering by release-acquire and by locks Alan Stern
2018-06-21 18:04 ` Peter Zijlstra
2018-06-22 3:34 ` Paul E. McKenney
2018-06-22 8:08 ` Peter Zijlstra
2018-06-22 8:09 ` Will Deacon
2018-06-22 9:55 ` Will Deacon
2018-06-22 10:31 ` Peter Zijlstra
2018-06-22 10:38 ` Will Deacon
2018-06-22 11:25 ` Andrea Parri
2018-06-22 16:40 ` Paul E. McKenney
2018-06-22 18:09 ` Alan Stern
2018-06-22 18:30 ` Will Deacon
2018-06-22 19:11 ` Alan Stern
2018-06-22 20:53 ` Paul E. McKenney
2018-07-04 11:53 ` Will Deacon
2018-06-25 8:19 ` Andrea Parri [this message]
2018-07-03 17:28 ` Alan Stern
2018-07-04 11:28 ` Paul E. McKenney
2018-07-04 12:13 ` Will Deacon
2018-07-05 14:23 ` Alan Stern
2018-07-05 15:31 ` Paul E. McKenney
2018-07-04 12:11 ` Will Deacon
2018-07-05 14:00 ` Andrea Parri
2018-07-05 14:44 ` Will Deacon
2018-07-05 15:16 ` Daniel Lustig
2018-07-05 15:35 ` Daniel Lustig
2018-07-05 14:21 ` Alan Stern
2018-07-05 14:46 ` Will Deacon
2018-07-05 14:57 ` Alan Stern
2018-07-05 15:15 ` Will Deacon
2018-07-05 15:09 ` Andrea Parri
2018-07-06 20:37 ` Alan Stern
2018-07-06 21:10 ` Paul E. McKenney
2018-07-09 16:52 ` Will Deacon
2018-07-09 17:29 ` Daniel Lustig
2018-07-09 19:18 ` Alan Stern
2018-07-05 15:31 ` Paul E. McKenney
2018-07-05 15:39 ` Andrea Parri
2018-07-05 16:58 ` Paul E. McKenney
2018-07-05 17:06 ` Andrea Parri
2018-07-05 15:44 ` Daniel Lustig
2018-07-05 16:22 ` Will Deacon
2018-07-05 16:56 ` Paul E. McKenney
2018-07-05 18:12 ` Daniel Lustig
2018-07-05 18:38 ` Andrea Parri
2018-07-05 18:44 ` Andrea Parri
2018-07-05 23:32 ` Paul E. McKenney
2018-07-05 23:31 ` Paul E. McKenney
2018-07-06 9:25 ` Will Deacon
2018-07-06 14:14 ` Paul E. McKenney
2018-06-25 7:32 ` Peter Zijlstra
2018-06-25 8:29 ` Andrea Parri
2018-06-25 9:06 ` Peter Zijlstra
2018-06-22 9:06 ` Andrea Parri
2018-06-22 19:23 ` Alan Stern
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