From: Andrea Parri <andrea.parri@amarulasolutions.com>
To: "Paul E. McKenney" <paulmck@linux.ibm.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 10:17:38 +0200 [thread overview]
Message-ID: <20190427081738.GA11149@andrea> (raw)
In-Reply-To: <20190423133010.GK3923@linux.ibm.com>
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
next prev parent reply other threads:[~2019-04-27 8:17 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 [this message]
2019-04-27 8:36 ` Paul E. McKenney
2019-04-29 9:24 ` Johan Hovold
2019-04-29 14:49 ` Paul E. McKenney
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190427081738.GA11149@andrea \
--to=andrea.parri@amarulasolutions.com \
--cc=akiyks@gmail.com \
--cc=boqun.feng@gmail.com \
--cc=dhowells@redhat.com \
--cc=dlustig@nvidia.com \
--cc=j.alglave@ucl.ac.uk \
--cc=linux-kernel@vger.kernel.org \
--cc=luc.maranget@inria.fr \
--cc=npiggin@gmail.com \
--cc=paulmck@linux.ibm.com \
--cc=peterz@infradead.org \
--cc=stern@rowland.harvard.edu \
--cc=will.deacon@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.