Messages in this thread | | | Date | Sun, 03 Jun 2012 17:03:50 +0530 | From | "Srivatsa S. Bhat" <> | Subject | Re: [PATCH 01/27] smpboot: Provide a generic method to boot secondary processors |
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On 06/03/2012 02:23 PM, Yong Zhang wrote:
> On Fri, Jun 01, 2012 at 05:39:27PM +0530, Srivatsa S. Bhat wrote: >> +void __cpuinit smpboot_start_secondary(void *arg) >> +{ >> + unsigned int cpu; >> + >> + /* >> + * SMP booting is extremely fragile in some architectures. So run >> + * the cpu initialization code first before anything else. >> + */ >> + __cpu_pre_starting(arg); >> + >> + preempt_disable(); >> + cpu = smp_processor_id(); >> + >> + /* Invoke the CPU_STARTING notifier callbacks */ >> + notify_cpu_starting(cpu); >> + >> + __cpu_pre_online(arg); >> + >> + /* Set the CPU in the cpu_online_mask */ >> + set_cpu_online(cpu, true); >> + >> + __cpu_post_online(arg); >> + > > Seems it worth to catch incorrect irq state here: > > WARN_ON_ONCE(!irqs_disabled()); >
That's a good point! But unfortunately we can't do that just yet. Because, some architectures have explicit comments that say that irqs must be enabled at a certain point in time, or have something special than just a local_irq_enable(), and hence fall under the __cpu_post_online() function when converted to this model.
Examples: ARM (patch 26) and ia64 (patch 15)
Unless the maintainers give a go-ahead to change them, I don't think it would be safe.. (I have added the Notes section to each patch to get the attention of the maintainers to such issues).
Regards, Srivatsa S. Bhat
> >> + /* Enable local interrupts now */ >> + local_irq_enable(); >> + >> + wmb(); >> + cpu_idle(); >> + >> + /* We should never reach here! */ >> + BUG(); >> +}
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