Messages in this thread | | | Date | Sun, 03 Jun 2012 16:52:23 +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 02:21 PM, Yong Zhang wrote:
> On Fri, Jun 01, 2012 at 05:39:27PM +0530, Srivatsa S. Bhat wrote: >> +/* Implement the following functions in your architecture, as appropriate. */ >> + >> +/** >> + * __cpu_pre_starting() >> + * >> + * Implement whatever you need to do before the CPU_STARTING notifiers are >> + * invoked. Note that the CPU_STARTING callbacks run *on* the cpu that is >> + * coming up. So that cpu better be prepared! IOW, implement all the early >> + * boot/init code for the cpu here. And do NOT enable interrupts. >> + */ >> +#ifndef __cpu_pre_starting > > Why the ifndef? >
In short, to avoid breaking build on x86. We wanted to follow the x86 convention of having static inline functions in arch/x86/include/asm/smp.h and use the smp_ops structure to route the calls to x86 or xen as appropriate (see patch 4 in this series).
But __weak definitions interfere with that and break the build. Hence, we followed what Linus suggested doing in a similar context: https://lkml.org/lkml/2008/7/26/187
Regards, Srivatsa S. Bhat
>
>> +void __weak __cpu_pre_starting(void *arg) {} >> +#endif >> + >> +/** >> + * __cpu_pre_online() >> + * >> + * Implement whatever you need to do before the upcoming CPU is set in the >> + * cpu_online_mask. (Setting the cpu in the cpu_online_mask is like an >> + * announcement that the cpu has come up, because it would be publicly >> + * visible now). Again, don't enable interrupts. >> + */ >> +#ifndef __cpu_pre_online >> +void __weak __cpu_pre_online(void *arg) {} >> +#endif >> +
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