From: "Paul E. McKenney" <paulmck@linux.ibm.com>
To: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Nicholas Piggin <npiggin@gmail.com>,
LKMM Maintainers -- Akira Yokosawa <akiyks@gmail.com>,
Boqun Feng <boqun.feng@gmail.com>,
David Howells <dhowells@redhat.com>,
Daniel Lustig <dlustig@nvidia.com>,
Jade Alglave <j.alglave@ucl.ac.uk>,
Kernel development list <linux-kernel@vger.kernel.org>,
Luc Maranget <luc.maranget@inria.fr>,
Alan Stern <stern@rowland.harvard.edu>,
Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH] Documentation: atomic_t.txt: Explain ordering provided by smp_mb__{before,after}_atomic()
Date: Sat, 27 Apr 2019 01:36:29 -0700 [thread overview]
Message-ID: <20190427083629.GJ3923@linux.ibm.com> (raw)
In-Reply-To: <20190427081738.GA11149@andrea>
On Sat, Apr 27, 2019 at 10:17:38AM +0200, Andrea Parri wrote:
> On Tue, Apr 23, 2019 at 06:30:10AM -0700, Paul E. McKenney wrote:
> > On Tue, Apr 23, 2019 at 02:32:09PM +0200, Peter Zijlstra wrote:
> > > On Sat, Apr 20, 2019 at 01:54:40AM -0700, Paul E. McKenney wrote:
> > > > And atomic_set(): set_preempt_state(). This fails
> > > > on x86, s390, and TSO friends, does it not? Or is
> > > > this ARM-only? Still, why not just smp_mb() before and
> > > > after? Same issue in __kernfs_new_node(), bio_cnt_set(),
> > > > sbitmap_queue_update_wake_batch(),
> > > >
> > > > Ditto for atomic64_set() in __ceph_dir_set_complete().
> > > >
> > > > Ditto for atomic_read() in rvt_qp_is_avail(). This function
> > > > has a couple of other oddly placed smp_mb__before_atomic().
> > >
> > > That are just straight up bugs. The atomic_t.txt file clearly specifies
> > > the barriers only apply to RmW ops and both _set() and _read() are
> > > specified to not be a RmW.
> >
> > Agreed. The "Ditto" covers my atomic_set() consternation. ;-)
>
> I was working on some of these before the Easter break [1, 2]: the plan
> was to continue next week, but by addressing the remaining cases with a
> conservative s/that barrier/smp_mb at first; unless you've other plans?
>
> Andrea
>
> [1] http://lkml.kernel.org/r/1555417031-27356-1-git-send-email-andrea.parri@amarulasolutions.com
> [2] http://lkml.kernel.org/r/1555404968-39927-1-git-send-email-pbonzini@redhat.com
Sounds good to me! ;-)
Thanx, Paul
next prev parent reply other threads:[~2019-04-27 8:37 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-19 17:21 [PATCH] Documentation: atomic_t.txt: Explain ordering provided by smp_mb__{before,after}_atomic() Alan Stern
2019-04-19 17:54 ` Paul E. McKenney
2019-04-19 18:00 ` Peter Zijlstra
2019-04-19 18:26 ` Paul E. McKenney
2019-04-20 0:26 ` Nicholas Piggin
2019-04-20 8:54 ` Paul E. McKenney
2019-04-23 12:17 ` Peter Zijlstra
2019-04-23 13:21 ` Paul E. McKenney
2019-04-23 13:26 ` Peter Zijlstra
2019-04-23 20:16 ` Paul E. McKenney
2019-04-23 20:28 ` Peter Zijlstra
2019-04-24 8:29 ` Paul E. McKenney
2019-04-24 8:44 ` Peter Zijlstra
2019-04-23 12:32 ` Peter Zijlstra
2019-04-23 13:30 ` Paul E. McKenney
2019-04-23 13:40 ` Peter Zijlstra
2019-04-23 20:19 ` Paul E. McKenney
2019-04-27 8:17 ` Andrea Parri
2019-04-27 8:36 ` Paul E. McKenney [this message]
2019-04-29 9:24 ` Johan Hovold
2019-04-29 14:49 ` Paul E. McKenney
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