Re: [Xen-devel] [PATCH 2/3] xen/sched: remove cpu from pool0 before removing it

From: Dario Faggioli <dfaggioli@suse.com>
To: Juergen Gross <JGross@suse.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: "sstabellini@kernel.org" <sstabellini@kernel.org>,
	"wl@xen.org" <wl@xen.org>,
	"konrad.wilk@oracle.com" <konrad.wilk@oracle.com>,
	"George.Dunlap@eu.citrix.com" <George.Dunlap@eu.citrix.com>,
	"ian.jackson@eu.citrix.com" <ian.jackson@eu.citrix.com>,
	"tim@xen.org" <tim@xen.org>,
	"julien.grall@arm.com" <julien.grall@arm.com>,
	Jan Beulich <JBeulich@suse.com>,
	"andrew.cooper3@citrix.com" <andrew.cooper3@citrix.com>
Subject: Re: [Xen-devel] [PATCH 2/3] xen/sched: remove cpu from pool0 before removing it
Date: Tue, 13 Aug 2019 17:11:36 +0000	[thread overview]
Message-ID: <207a0624d8ea32e46694a31716e79b7f2ed4cce8.camel@suse.com> (raw)
In-Reply-To: <20190802130730.15942-3-jgross@suse.com>

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On Fri, 2019-08-02 at 15:07 +0200, Juergen Gross wrote:
> Today a cpu which is removed from the system is taken directly from
> Pool0 to the offline state. This will conflict with the new idle
> scheduler, so remove it from Pool0 first. Additionally accept
> removing
> a free cpu instead of requiring it to be in Pool0.
> 
> For the resume failed case we need to call the scheduler code for
> that
> situation after the cpupool handling, so move the scheduler code into
> a function and call it from cpupool_cpu_remove_forced() and remove
> the
> CPU_RESUME_FAILED case from cpu_schedule_callback().
> 
> Note that we are calling now schedule_cpu_switch() in stop_machine
> context so we need to switch from spinlock_irq to spinlock_irqsave.
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>
> ---
> 
> --- a/xen/common/cpupool.c
> +++ b/xen/common/cpupool.c
> @@ -282,22 +282,14 @@ static int cpupool_assign_cpu_locked(struct
> cpupool *c, unsigned int cpu)
>      return 0;
>  }
>  
> -static long cpupool_unassign_cpu_helper(void *info)
> +static int cpupool_unassign_cpu_epilogue(struct cpupool *c)
>
in schedule.c, for a similar situation, we have used '_start' and
'_finish' as suffixes. What do you think about using those here too?

It's certainly a minor thing, I know, but I (personally) like them
better (especially than 'epilogue') and I think it gives us some
consistency (yes, sure, different files.. but scheduling and cpupools
are quite tightly related).

Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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