Hi Russell, On 11/10/2015 9:55 PM, Russell King - ARM Linux wrote: > On Tue, Nov 10, 2015 at 09:33:12PM +0530, Kapil Hali wrote: >> Hi Russel, > > Wrong. Look at my name as sent in the From: and as quoted in the very > next line. As far as I'm concerned (and I don't care what other people > say) it's disrespectful to spell people's names incorrectly. > I am sincerely apologetic about it. It was a deviation that will not repeat again. >> It was clear the very first time itself as pointed out by you and the >> lead developers and hence the change was readily sent in the very next >> patch set. I didn't change a comment in this patch, which is misleading >> about the SMP enable-method used in the patch set, it is my mistake and >> I apologies for the same. I will change it and send the next patch set. > > Thanks. > >> Also, before sending out the patch set, I had asked for a clarification >> about the method: https://lkml.org/lkml/2015/11/6/234 > > Sorry, I don't read every single email irrespective of how it's marked. > There's way too much email, and way too much mail with improperly > classified recipient lists to be able to usefully sort this mail. > (If you do the math, the email rate during a 12 hour working day from > just linux-arm-kernel is one email every 2.5 minutes, assuming 300 emails > a day. It takes way longer than that to compose a proper reply to an > email - I've spent around 15 minutes on this one alone. Hence, if I'm > busy, I more or less totally ignore email now, and rarely bother to > "catch up" with missed emails.) > >> For my understanding, I am repeating my query- In case of simple method of >> waking up secondary core, smp_boot_secondary() will always return success >> indicating secondary core successfully started. I understand that in >> __cpu_up(), primary core waits for completion till secondary core comes >> online or time outs. However, is it appropriate to return successful start >> of secondary core without knowing if it really did? > > Yes, because all that your smp_boot_secondary() should be doing is > trying to start the core. If you encounter an error trying to do so, > that's what the error return is for. > > If you just set a bit somewhere to tell the hardware to release the > secondary core's reset, then if you set the bit and return success, > that's prefectly acceptable. The core ARM SMP code will then wait > up to one second for the secondary core to become known to the kernel > before declaring that the CPU failed to come online. > > If it fails to appear, we assume that it will never appear - and > actually at that point the system is in an unknown state: if the > secondary CPU crashed during its boot, it could start scribbling > into memory or touching devices in an unpredictable way: the only > sane answer is to reboot the whole system to ensure that it's back > to a known good state. Hence why we don't provide any cleanup at > the point of a failed secondary CPU (I've been debating about > tainting the kernel at that point, so we know when things have > gone bad.) > > Hope this helps. > Surely it has helped and many thanks for your detailed explanation. Thanks, Kapil Hali -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
