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Re: [PATCH] kvm: fix waitqueue_active without memory barrier in virt/kvm/async_pf.c

From Paolo Bonzini <pbonzini@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH] kvm: fix waitqueue_active without memory barrier in virt/kvm/async_pf.c
Date 2015-10-09 12:30 +0200
Message-ID <qhD61-7Lm-9@gated-at.bofh.it> (permalink)
References <qhBxg-5rH-23@gated-at.bofh.it> <qhBQC-63L-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On 09/10/2015 11:04, Kosuke Tatsukawa wrote:
> smp_store_mb() called from set_current_state(), which is called from
> prepare_to_wait() should prevent reordering such as below from
> happening.  wait_event*() also calls set_current_state() inside.

Ah, I missed that set_current_state has a memory barrier in it.  The
patch is okay, but please expand the comment to say that this memory
barrier pairs with prepare_to_wait's set_current_state().

Paolo
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Thread

[PATCH] kvm: fix waitqueue_active without memory barrier in  virt/kvm/async_pf.c Kosuke Tatsukawa <tatsu@ab.jp.nec.com> - 2015-10-09 02:40 +0200
  Re: [PATCH] kvm: fix waitqueue_active without memory barrier in  virt/kvm/async_pf.c Paolo Bonzini <pbonzini@redhat.com> - 2015-10-09 10:50 +0200
    Re: [PATCH] kvm: fix waitqueue_active without memory barrier in  virt/kvm/async_pf.c Peter Zijlstra <peterz@infradead.org> - 2015-10-09 11:00 +0200
      Re: [PATCH] kvm: fix waitqueue_active without memory barrier in  virt/kvm/async_pf.c Paolo Bonzini <pbonzini@redhat.com> - 2015-10-09 12:30 +0200
    Re: [PATCH] kvm: fix waitqueue_active without memory barrier in  virt/kvm/async_pf.c  Kosuke Tatsukawa <tatsu@ab.jp.nec.com> - 2015-10-09 11:10 +0200
      Re: [PATCH] kvm: fix waitqueue_active without memory barrier in  virt/kvm/async_pf.c Paolo Bonzini <pbonzini@redhat.com> - 2015-10-09 12:30 +0200
        Re: [PATCH] kvm: fix waitqueue_active without memory barrier in  virt/kvm/async_pf.c  Kosuke Tatsukawa <tatsu@ab.jp.nec.com> - 2015-10-09 14:30 +0200

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