linux-kernel - Re: [PATCH 10/27] mips, smpboot: Use generic SMP booting infrastructure

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Date:	Sun, 03 Jun 2012 17:18:16 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Yong Zhang <yong.zhang0@...il.com>
CC:	tglx@...utronix.de, peterz@...radead.org,
	paulmck@...ux.vnet.ibm.com, rusty@...tcorp.com.au,
	mingo@...nel.org, akpm@...ux-foundation.org,
	vatsa@...ux.vnet.ibm.com, rjw@...k.pl, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org, nikunj@...ux.vnet.ibm.com,
	Ralf Baechle <ralf@...ux-mips.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Mike Frysinger <vapier@...too.org>,
	David Howells <dhowells@...hat.com>,
	Arun Sharma <asharma@...com>, linux-mips@...ux-mips.org
Subject: Re: [PATCH 10/27] mips, smpboot: Use generic SMP booting infrastructure

On 06/03/2012 01:55 PM, Yong Zhang wrote:

> On Fri, Jun 01, 2012 at 02:42:32PM +0530, Srivatsa S. Bhat wrote:
>> Convert mips to use the generic framework to boot secondary CPUs.
>>
>> Notes:
>> 1. The boot processor was setting the secondary cpu in cpu_online_mask!
>> Instead, leave it up to the secondary cpu (... and it will be done by the
>> generic code now).
>>
>> 2. Make the boot cpu wait for the secondary cpu to be set in cpu_online_mask
>> before returning.
> 
> We don't need to wait for both cpu_callin_map (The code above yours)
> any more.


Yes, I noticed that while writing the patch. But then, I thought of cleaning
up the hundreds of callin/callout/commenced maps in various architectures and
bringing them out into core code in a later series, and clean this up at that time..
I didn't want to do too many invasive changes all at one-shot.

But I guess for this particular case of mips, I can get rid of the wait for
cpu_callin_map in this patchset itself. I'll update this patch with that change.

Thanks!

> 
>>
>> 3. Don't enable interrupts in cmp_smp_finish() and vsmp_smp_finish().
>> Do it much later, in generic code.
> 
> Hmmm... the bad thing is that some board enable irq more early than
> ->smp_finish(), I have sent patches for that (by moving irq enable
> to smp_finish() and delaying smp_finish()).
> Please check patch#0001~patch#0004 in
> http://marc.info/?l=linux-mips&m=133758022710973&w=2
> 
>>
>> 4. In synchronise_count_slave(), use local_save_flags() instead of
>> local_irq_save() because irqs are still disabled.
> 
> We can just remove local_irq_save()/local_irq_restore() like:
> http://marc.info/?l=linux-mips&m=133758046211043&w=2
> 


So what is the status of those patches? Has anyone picked them up?

I could rebase this patch on top of yours, or better yet, if your
patches haven't been picked up yet, I could include them in this
patchset itself to avoid too many dependencies on external patches.

What do you say?

Regards,
Srivatsa S. Bhat

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