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Re: [RESEND PATCH v5] locking/pvqspinlock: Relax cmpxchg's to improve performance on some archs

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [RESEND PATCH v5] locking/pvqspinlock: Relax cmpxchg's to improve performance on some archs
Date 2017-08-14 20:50 +0200
Message-ID <uesB5-7Hs-37@gated-at.bofh.it> (permalink)
References (4 earlier) <ucYlH-806-3@gated-at.bofh.it> <ucYvo-83r-25@gated-at.bofh.it> <ud0dQ-Jr-15@gated-at.bofh.it> <ude78-1CC-17@gated-at.bofh.it> <uemlX-3Zn-9@gated-at.bofh.it>
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On Mon, Aug 14, 2017 at 01:01:22PM +0100, Will Deacon wrote:
> Yeah, that's right, you can't use the STXR status flag to create control
> dependencies.

Just for my elucidation; you can't use it to create a control dependency
on the store, but you can use it to create a control dependency on the
corresponding load, right?

Now, IIRC, we've defined control dependencies as being LOAD->STORE
ordering, so in that respect nothing is lost. But maybe we should
explicitly mention that if the LOAD is part of an (otherwise) atomic RmW
the STORE is not constrained.

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Re: [RESEND PATCH v5] locking/pvqspinlock: Relax cmpxchg's to  improve performance on some archs Will Deacon <will.deacon@arm.com> - 2017-08-14 14:10 +0200
  Re: [RESEND PATCH v5] locking/pvqspinlock: Relax cmpxchg's to improve  performance on some archs Waiman Long <longman@redhat.com> - 2017-08-14 17:10 +0200
    Re: [RESEND PATCH v5] locking/pvqspinlock: Relax cmpxchg's to  improve performance on some archs Will Deacon <will.deacon@arm.com> - 2017-08-14 18:10 +0200
  Re: [RESEND PATCH v5] locking/pvqspinlock: Relax cmpxchg's to  improve performance on some archs Peter Zijlstra <peterz@infradead.org> - 2017-08-14 20:50 +0200
    Re: [RESEND PATCH v5] locking/pvqspinlock: Relax cmpxchg's to  improve performance on some archs Will Deacon <will.deacon@arm.com> - 2017-08-15 20:50 +0200
      Re: [RESEND PATCH v5] locking/pvqspinlock: Relax cmpxchg's to  improve performance on some archs Peter Zijlstra <peterz@infradead.org> - 2017-08-21 13:00 +0200
        Re: [RESEND PATCH v5] locking/pvqspinlock: Relax cmpxchg's to  improve performance on some archs Will Deacon <will.deacon@arm.com> - 2017-08-21 20:10 +0200
          Re: [RESEND PATCH v5] locking/pvqspinlock: Relax cmpxchg's to  improve performance on some archs Peter Zijlstra <peterz@infradead.org> - 2017-08-21 21:30 +0200
            Re: [RESEND PATCH v5] locking/pvqspinlock: Relax cmpxchg's to  improve performance on some archs Peter Zijlstra <peterz@infradead.org> - 2017-08-21 21:50 +0200
              Re: [RESEND PATCH v5] locking/pvqspinlock: Relax cmpxchg's to improve  performance on some archs Waiman Long <longman@redhat.com> - 2017-08-22 17:40 +0200
            Re: [RESEND PATCH v5] locking/pvqspinlock: Relax cmpxchg's to  improve performance on some archs Will Deacon <will.deacon@arm.com> - 2017-08-22 12:50 +0200

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