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Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , "mingo@redhat.com" , Will Deacon Subject: Re: [PATCH v1 2/2] x86/hyperv: make HvNotifyLongSpinWait hypercall Message-ID: <20181022171516.GH3117@worktop.programming.kicks-ass.net> References: <1539954835-34035-1-git-send-email-yi.y.sun@linux.intel.com> <1539954835-34035-3-git-send-email-yi.y.sun@linux.intel.com> <20181022015342.GK11769@yi.y.sun> <2e0d62cb-b706-a5b4-65f7-982a913fb32b@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Firstly, who come a patch that is grubbing around in kernel/locking/ has an x86/hyperv subject and isn't Cc'ed to the locking maintainers? On Mon, Oct 22, 2018 at 12:31:45PM -0400, Waiman Long wrote: > On 10/22/2018 03:32 AM, Juergen Gross wrote: > > On 22/10/2018 03:53, Yi Sun wrote: > >> On 18-10-19 16:20:52, Juergen Gross wrote: > >>> On 19/10/2018 15:13, Yi Sun wrote: > >> [...] > >> > >>>> diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h > >>>> index 0130e48..9e88c7e 100644 > >>>> --- a/kernel/locking/qspinlock_paravirt.h > >>>> +++ b/kernel/locking/qspinlock_paravirt.h > >>>> @@ -7,6 +7,8 @@ > >>>> #include > >>>> #include > >>>> > >>>> +#include > >>>> + > >>>> /* > >>>> * Implement paravirt qspinlocks; the general idea is to halt the vcpus instead > >>>> * of spinning them. > >>>> @@ -305,6 +307,10 @@ static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev) > >>>> wait_early = true; > >>>> break; > >>>> } > >>>> +#if defined(CONFIG_X86_64) && defined(CONFIG_PARAVIRT_SPINLOCKS) && IS_ENABLED(CONFIG_HYPERV) > >>>> + if (!hv_notify_long_spin_wait(SPIN_THRESHOLD - loop)) > >>>> + break; > >>>> +#endif Secondly; how come you thought that was acceptable in any way shape or form? > > vcpu_is_preempted() is already part of this loop. And this is a paravirt > > hook. Can't you make use of that? This might require adding another > > parameter to this hook, but I'd prefer that over another pv-spinlock > > hook. > I agree with Juergen on that. I would suggest rename the > vcpu_is_preempted hook into a more generic vcpu_stop_spinning, perhaps, > so different hypervisors can act on the information accordingly. Adding > an extra parameter is fine. No; no extra parameters. vcpu_is_preempted() is a simple and intuitive interface. Why would we want to make it complicated?