linux-kernel - Re: [PATCH v7 5/9] x86/smpboot: Split up native_cpu_up into separate phases and document them

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Date:   Wed, 08 Feb 2023 12:02:55 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Yuan Yao <yuan.yao@...ux.intel.com>,
        Usama Arif <usama.arif@...edance.com>
Cc:     tglx@...utronix.de, kim.phillips@....com, arjan@...ux.intel.com,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, x86@...nel.org, pbonzini@...hat.com,
        paulmck@...nel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, rcu@...r.kernel.org, mimoja@...oja.de,
        hewenliang4@...wei.com, thomas.lendacky@....com, seanjc@...gle.com,
        pmenzel@...gen.mpg.de, fam.zheng@...edance.com,
        punit.agrawal@...edance.com, simon.evans@...edance.com,
        liangma@...ngbit.com
Subject: Re: [PATCH v7 5/9] x86/smpboot: Split up native_cpu_up into
 separate phases and document them

On Wed, 2023-02-08 at 18:03 +0800, Yuan Yao wrote:
> 
> >   #endif
> > +       /*
> > +        * Sync point with do_wait_cpu_initialized(). On boot, all secondary
> > +        * CPUs reach this stage after receiving INIT/SIPI from do_cpu_up()
> > +        * in the x86/cpu:kick cpuhp stage. At the start of cpu_init() they
> > +        * will wait for do_wait_cpu_initialized() to set their bit in
> > +        * smp_callout_mask to release them.
> 
> The last sentence of the comment looks confused. The fact is:
> 
> For serial case, The BSP waits AP to set cpu_initialized_mask from
> wait_for_master_cpu() after fired INIT/SIPI, then AP starts to wait
> cpu_callout_mask set by BSP from do_boot_cpu().
> 
> Or the comments below "Bringup step two:..." which also looks clear
> enough then above.


	/*
	 * Sync point with do_wait_cpu_initialized(). Before proceeding through
	 * cpu_init(), the AP will call wait_for_master_cpu() which sets its
	 * bit in cpu_initialized_mask and then waits for the BSP to set its
	 * bit in cpu_callout_mask to release it.
	 */
	cpu_init_secondary();


Better?

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