On 06/04/2012 07:59 PM, Thomas Gleixner wrote: > On Fri, 1 Jun 2012, Srivatsa S. Bhat wrote: >> From: Nikunj A. Dadhania <nikunj@xxxxxxxxxxxxxxxxxx> >> >> Convert x86 to use the generic framework to boot secondary CPUs. >> >> Notes: >> 1. x86 manipulates the cpu_online_mask under vector_lock. So, while >> converting over to the generic smp booting code, override arch_vector_lock() >> and arch_vector_unlock() to lock_vector_lock() and unlock_vector_lock() >> respectively. >> >> 2. In smp_callin(), we allow the master to continue as soon as the physical >> booting of the secondary processor is done. That is, we don't wait till the >> CPU_STARTING notifications are sent. >> >> Implications: >> - This does not alter the order in which the notifications are sent (i.e., >> still CPU_STARTING is followed by CPU_ONLINE) because the master waits till >> the new cpu is set in the cpu_online_mask before returning to generic code. >> >> - This approach is better because of 2 reasons: >> a. It makes more sense: the master has a timeout for waiting on the >> cpu_callin_map - which means we should report back as soon as possible. >> The whole idea of having a timeout is to estimate the maximum time that >> could be taken for physical booting. This approach separates out the >> physical booting vs running CPU hotplug callbacks and reports back to >> the master as soon as physical booting is done. > > How do you deal with the problem that the master does not come back in > time? Sorry, I didn't quite get your point... This doesn't completely solve the timeout problem, but makes the situation a little bit better, that's all. > There is a timeout on the booting side as well. Yes, the wait for the cpu_callout_mask. > I haven't found > out why this timeout exists at all, but we need to take care of that > and there is a patch on LKML which removes the panic as this can > happen on virt. Oh! Ok.. > I really wonder whether the hardware for which this > timeout stuff was introduced still exists or whether we can simply get > rid of it completely. > Sounds good :-) > Also the whole callin/callout mask business wants to be in the generic > code. It can be replaced completely by cpu_state, at least that's what > I was aiming for. There is no need for several variables tracking the > same thing in different ways. > Exactly! I was thinking of consolidating the callin/callout/commenced/whatever mask in various architectures in a future patchset. I haven't touched them in this one. And using cpu_state for that is a very good point. I'll keep that in mind, thanks! Regards, Srivatsa S. Bhat -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
