From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH] xen: arm: wait 1000ms for a CPU to come up, instead of forever Date: Wed, 14 Jan 2015 15:11:37 +0000 Message-ID: <54B68729.4040908@linaro.org> References: <1421244060-1745-1-git-send-email-ian.campbell@citrix.com> <54B67CCA.9060205@linaro.org> <1421246359.19103.269.camel@citrix.com> <54B68265.20001@linaro.org> <1421247394.19103.273.camel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1421247394.19103.273.camel@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: stefano.stabellini@eu.citrix.com, tim@xen.org, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 14/01/15 14:56, Ian Campbell wrote: >>> Where do you mean exactly? >> >> See for instance exynos5_cpu_power_up. > > Appears to be waiting the h/w to acknowledge that the CPU power is on, > which is no guarantee that it is going to actually boot, or even make it > to Xen code. Right. This is what I was trying to say. >> >>>> >>>>> + >>>>> + while ( !cpu_online(cpu) && NOW() < deadline ) >>>>> { >>>>> cpu_relax(); >>>>> process_pending_softirqs(); >>>>> } >>>>> >>>>> + /* >>>>> + * Nuke start of day info before checking one last time if the CPU >>>>> + * actually came online. >>>>> + * >>>>> + * Doesn't completely avoid the posibility of it trying to >>>>> + * progress with another CPUs stack etc, but better than nothing, >>>>> + * hopefully. >>>>> + */ >>>>> + init_data.stack = NULL; >>>>> + init_data.cpuid = ~0; >>>>> + smp_up_cpu = MPIDR_INVALID; >>>>> + clean_dcache(smp_up_cpu); >>>> >>>> I don't understand why you need to do this. Is it for pure clean up? If >>>> so, please explain it in the commit message. >>> >>> Is the comment right above it not sufficient explanation? I can insert >>> at the end of the first paragraph "If it is not online it may still be >>> trying and may show up later" is that would help. >> >> It's more clear for me with "If it is not online ...". >> >> For the second paragraph, I would say "It doesn't completely avoid ...". > > OK, I'll make both changes. > >> Also I was wondering if there is any possibility to turn off the cpu if >> it doesn't come online? > > PSCI has a cpu_off, and there will be arch specific mechanisms. Whether > they will work under the circumstances is hard to say. In any case that > is out of scope for this patch. True. I will give a look later when I will have time. With the change in the comment: Reviewed-by: Julien Grall Regards, -- Julien Grall