Messages in this thread | | | Date | Tue, 29 Jul 2008 07:31:49 -0700 | From | Mike Travis <> | Subject | Re: linux-next: build failure |
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Ingo Molnar wrote: > * KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote: > >>> * Stephen Rothwell <sfr@canb.auug.org.au> wrote: >>> >>>> Hi Ingo, >>>> >>>> On Tue, 29 Jul 2008 10:00:55 +0200 Ingo Molnar <mingo@elte.hu> wrote: >>>>>> -#define cpumask_of_cpu(cpu) ({ *get_cpu_mask(cpu); }) >>>>>> +#define cpumask_of_cpu(cpu) (*get_cpu_mask(cpu)) >>>>> hm, i'm wondering - is this a compiler bug? >>>> Or maybe a deficiency in such an old compiler (v3.4.5) but the fix >>>> makes sense anyway, right? >>> yeah, i was just wondering. >> in linux/README >> >> COMPILING the kernel: >> >> - Make sure you have at least gcc 3.2 available. >> For more information, refer to Documentation/Changes. >> >> So, if 3.4.5 is old, Should we change readme? > > the fix is simple enough. > > but the question is, wont it generate huge artificial stackframes with > CONFIG_MAXSMP and NR_CPUS=4096? Maybe it is unable to figure out and > simplify the arithmetics there - or something like that. > > Ingo
I've looked at stack frames quite extensively and usually they are not generated unless you explicitly use a named cpumask variable, pass a cpumask by value, expect a cpumask function return, create an initializer that contains a cpumask field, and (probably a couple more I missed).
Almost all others are done efficiently via pointers or simple struct copies:
cpus_xxx(*cpumask_of_cpu(), ... struct->cpumask_var = *cpumask_of_cpu() global_cpumask_var = *cpumask_of_cpu() etc.
Thanks, Mike
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