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SubjectRe: mm/percpu.c: use smarter memory allocation for struct pcpu_alloc_info (crisv32 hang)
On Mon, Nov 27, 2017 at 03:51:04PM -0500, Nicolas Pitre wrote:
> On Mon, 27 Nov 2017, Tejun Heo wrote:
>
> > Hello,
> >
> > On Mon, Nov 27, 2017 at 03:31:52PM -0500, Nicolas Pitre wrote:
> > > So IMHO I don't think reverting the commit is the right thing to do.
> > > That commit is clearly not at fault here.
> >
> > It's not about the blame. We just want to avoid breaking boot in a
> > way which is difficult to debug. Once cris is fixed, we can re-apply
> > the patch.
>
> In that case I suggest the following instead. No point penalizing
> everyone for a single architecture's fault. And this will serve as a
> visible reminder to the cris people that they need to clean up.
>
> ----- >8
> Subject: percpu: hack to let the CRIS architecture to boot until they clean up
>
> Commit 438a506180 ("percpu: don't forget to free the temporary struct
> pcpu_alloc_info") uncovered a problem on the CRIS architecture where
> the bootmem allocator is initialized with virtual addresses. Given it
> has:
>
> #define __va(x) ((void *)((unsigned long)(x) | 0x80000000))
>
> then things just work out because the end result is the same whether you
> give this a physical or a virtual address.
>
> Untill you call memblock_free_early(__pa(address)) that is, because
> values from __pa() don't match with the virtual addresses stuffed in the
> bootmem allocator anymore.
>
> Avoid freeing the temporary pcpu_alloc_info memory on that architecture
> until they fix things up to let the kernel boot like it did before.
>
> Signed-off-by: Nicolas Pitre <nico@linaro.org>
>
> diff --git a/mm/percpu.c b/mm/percpu.c
> index 79e3549cab..50e7fdf840 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -2719,7 +2719,11 @@ void __init setup_per_cpu_areas(void)
>
> if (pcpu_setup_first_chunk(ai, fc) < 0)
> panic("Failed to initialize percpu areas.");
> +#ifdef CONFIG_CRIS
> +#warning "the CRIS architecture has physical and virtual addresses confused"
> +#else
> pcpu_free_alloc_info(ai);
> +#endif
> }
>
> #endif /* CONFIG_SMP */

Works for me, and thanks.

/^JN - Jesper Nilsson
--
Jesper Nilsson -- jesper.nilsson@axis.com

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