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Re: [PATCH] locking/osq: Drop the overload of osq lock

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [PATCH] locking/osq: Drop the overload of osq lock
Date 2016-06-25 21:30 +0200
Message-ID <rO1rc-YJ-9@gated-at.bofh.it> (permalink)
References (1 earlier) <rNWKR-6yX-1@gated-at.bofh.it> <rNXxf-751-3@gated-at.bofh.it> <rNYtj-7Eq-13@gated-at.bofh.it> <rNYWl-7Oc-11@gated-at.bofh.it> <rNZz4-8h4-3@gated-at.bofh.it>
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On Sun, Jun 26, 2016 at 01:27:56AM +0800, panxinhui wrote:
> >> Would that not have issues where the owner cpu is kept running but the
> >> spinner (ie. _this_ vcpu) gets preempted? I would think that in that
> >> case we too want to stop spinning.
> >> 
> > 
> do  you mean that the spinner detect itself had yield out during the
> big spin loop?
> 
> It is very possible to happen.  BUT if spinner(on this vcpu) yield
> out, the next spinner would break the spin loop.  AND if spinner
> detect itself yield out once, it’s very possible to get the osq lock
> soon as long as the ower vcpu is running.
> 
> SO I think we need just check the owner vcpu’s yield_count.

I had a quick look at KVM and it looks like it only has
kvm_cpu::preempted, which would suggest the interface boqun proposed.

We'll have to look at many of the other virt platforms as well to see
what they can do.

We could also provide _both_ interfaces and a platform can implement
whichever variant (or both) it can.

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Thread

[PATCH] locking/osq: Drop the overload of osq lock Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-25 15:50 +0200
  Re: [PATCH] locking/osq: Drop the overload of osq lock Peter Zijlstra <peterz@infradead.org> - 2016-06-25 16:30 +0200
    Re: [PATCH] locking/osq: Drop the overload of osq lock Boqun Feng <boqun.feng@gmail.com> - 2016-06-25 17:20 +0200
      Re: [PATCH] locking/osq: Drop the overload of osq lock Peter Zijlstra <peterz@infradead.org> - 2016-06-25 18:10 +0200
        Re: [PATCH] locking/osq: Drop the overload of osq lock Peter Zijlstra <peterz@infradead.org> - 2016-06-25 18:20 +0200
          Re: [PATCH] locking/osq: Drop the overload of osq lock panxinhui <xinhui@linux.vnet.ibm.com> - 2016-06-25 19:30 +0200
            Re: [PATCH] locking/osq: Drop the overload of osq lock Peter Zijlstra <peterz@infradead.org> - 2016-06-25 21:20 +0200
              Re: [PATCH] locking/osq: Drop the overload of osq lock panxinhui <xinhui@linux.vnet.ibm.com> - 2016-06-26 07:00 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock Peter Zijlstra <peterz@infradead.org> - 2016-06-27 10:00 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-27 12:30 +0200
        Re: [PATCH] locking/osq: Drop the overload of osq lock Boqun Feng <boqun.feng@gmail.com> - 2016-06-25 18:30 +0200
          Re: [PATCH] locking/osq: Drop the overload of osq lock Peter Zijlstra <peterz@infradead.org> - 2016-06-25 20:30 +0200
      Re: [PATCH] locking/osq: Drop the overload of osq lock Peter Zijlstra <peterz@infradead.org> - 2016-06-25 18:20 +0200
        Re: [PATCH] locking/osq: Drop the overload of osq lock Boqun Feng <boqun.feng@gmail.com> - 2016-06-25 18:50 +0200
          Re: [PATCH] locking/osq: Drop the overload of osq lock panxinhui <xinhui@linux.vnet.ibm.com> - 2016-06-25 19:30 +0200
            Re: [PATCH] locking/osq: Drop the overload of osq lock Peter Zijlstra <peterz@infradead.org> - 2016-06-25 21:30 +0200
              Re: [PATCH] locking/osq: Drop the overload of osq lock Peter Zijlstra <peterz@infradead.org> - 2016-06-25 21:40 +0200
              Re: [PATCH] locking/osq: Drop the overload of osq lock Boqun Feng <boqun.feng@gmail.com> - 2016-06-26 04:30 +0200
              Re: [PATCH] locking/osq: Drop the overload of osq lock panxinhui <xinhui@linux.vnet.ibm.com> - 2016-06-26 07:30 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock Boqun Feng <boqun.feng@gmail.com> - 2016-06-26 08:10 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock panxinhui <xinhui@linux.vnet.ibm.com> - 2016-06-26 09:00 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock Boqun Feng <boqun.feng@gmail.com> - 2016-06-26 16:10 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock panxinhui <xinhui@linux.vnet.ibm.com> - 2016-06-26 18:00 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock Boqun Feng <boqun.feng@gmail.com> - 2016-06-26 09:00 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock panxinhui <xinhui@linux.vnet.ibm.com> - 2016-06-26 09:10 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock Boqun Feng <boqun.feng@gmail.com> - 2016-06-26 16:30 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock panxinhui <xinhui@linux.vnet.ibm.com> - 2016-06-26 17:20 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock Boqun Feng <boqun.feng@gmail.com> - 2016-06-27 08:50 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-27 09:40 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock Peter Zijlstra <peterz@infradead.org> - 2016-06-27 10:20 +0200
                Re: [PATCH] locking/osq: Drop the overload of osq lock Boqun Feng <boqun.feng@gmail.com> - 2016-06-27 12:30 +0200

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