linux-kernel - Re: [PATCH v2 for-4.17 0/3] Changes and clean-ups for spin_is

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Date:   Sun, 1 Apr 2018 18:33:02 +0200
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 for-4.17 0/3] Changes and clean-ups for
 spin_is_locked()

On Sat, Mar 31, 2018 at 04:29:40PM -0700, Paul E. McKenney wrote:
> On Sat, Mar 31, 2018 at 03:12:00PM +0200, Andrea Parri wrote:
> > On Fri, Mar 30, 2018 at 02:09:19PM +0200, Andrea Parri wrote:
> > > On Fri, Mar 30, 2018 at 01:36:45PM +0200, Ingo Molnar wrote:
> > > > 
> > > > (Paul and PeterZ Cc:-ed)
> > > > 
> > > > hi Andrea,
> > > > 
> > > > * Andrea Parri <andrea.parri@...rulasolutions.com> wrote:
> > > > 
> > > > > A resend of the "arch_spin_is_locked() patches" discussed in the last
> > > > > days,  together with a third patch/clean-up suggested by Will during
> > > > > the review procees.  The first two patches are unmodified, except for
> > > > > the inclusion of Acked-by:'s.
> > > > > 
> > > > > Cheers,
> > > > >   Andrea
> > > > > 
> > > > > Andrea Parri (3):
> > > > >   arm64: Remove smp_mb() from arch_spin_is_locked()
> > > > >   powerpc: Remove smp_mb() from arch_spin_is_locked()
> > > > >   locking: Clean-up comment and #ifndef for {,queued_}spin_is_locked()
> > > > > 
> > > > >  arch/arm64/include/asm/spinlock.h   | 5 -----
> > > > >  arch/powerpc/include/asm/spinlock.h | 1 -
> > > > >  include/asm-generic/qspinlock.h     | 2 --
> > > > >  include/linux/mutex.h               | 3 ---
> > > > >  4 files changed, 11 deletions(-)
> > > > 
> > > > Could you please also Cc: Paul to the next version of your series, who is usually 
> > > > collecting these patches? He might not have noticed these patches in the 
> > > > linux-kernel mailing list firehose which is way too high traffic.
> > > > 
> > > > Also, could you please use "git-send-email --no-chain-reply-to" or so, to make 
> > > > sure mails 1/2/3 properly email-chain off the mail 0 in a non-nested way? Right 
> > > > now the mails are 4 separate mails with nothing connecting them.
> > > 
> > > Absolutely. Thank you for the recommendations.
> > 
> > I'm planning to wait for some feedback on v2 before sending v3 (or pinging
> > on v2); please let me know if you'd prefer a RESEND of v2 instead.
> > 
> > Paul:
> > 
> > In the meantime, here are (for easy of reference) the message IDs of the 3
> > emails corresponding to the patches contained in this series/version:
> > 
> >   [1/3] arm64: Remove smp_mb() from arch_spin_is_locked()
> > 	<1522230419-12275-1-git-send-email-andrea.parri@...rulasolutions.com>
> > 
> >   [2/3] powerpc: Remove smp_mb() from arch_spin_is_locked()
> > 	<1522230457-12337-1-git-send-email-andrea.parri@...rulasolutions.com>
> > 
> >   [3/3] locking: Clean-up comment and #ifndef for {,queued_}spin_is_locked()
> > 	<1522230518-12398-1-git-send-email-andrea.parri@...rulasolutions.com>
> > 
> > The discussion on the previous/first version can be found here:
> > 
> > 	https://marc.info/?l=linux-kernel&m=152223054224291
> > 	https://marc.info/?l=linux-kernel&m=152223531625930&w=2
> > 
> > Please notice that these patches are all targetting 4.17. Also, 2/3 hasn't
> > been acked by the arch maintainers (so, we should hold off on this patch).
> 
> Agreed, plus a couple of the powerpc maintainers objected.  The smp_mb()
> isn't hurting anything given current use cases, so without their ack we
> should not push 2/3.
> 
> I suspec that we are a bit late for 4.17, but who knows?  If we are too
> late, 4.18 will be here before we know it.  Might need a bit of merging,
> but these patches should not be hard to merge, so this should not be a
> problem.
> 
> > Given these patches/discussion, you may want to also collect the (related):
> > 
> >   https://marc.info/?l=linux-kernel&m=151981440005264&w=2
> > 
> > (you were Cc-ed): this has been stalling since more than a couple of weeks
> > now, and I'm not aware of any objections to it.
> 
> Especially given that one of the objections from the powerpc maintainers
> was a lack of documentation.
> 
> In your v3, could you please send 1/3 and 3/3 along with the patch adding
> the docbook header to spin_is_locked() as a three-patch series using
> the method Ingo suggested?  I will pull it into my tree, and we can
> go from there.  If the powerpc maintainers change their minds on 2/3,
> we can pull that in as well.  (And I am back home, so should be a bit
> more responsive than I have been for the past four weeks!)

Nice! The new series is already on its way... Thanks,

  Andrea


> 
> 							Thanx, Paul
> 
> >   Andrea
> > 
> > 
> > > 
> > >   Andrea
> > > 
> > > 
> > > > 
> > > > Thanks,
> > > > 
> > > > 	Ingo
> > 
>