Messages in this thread Patch in this message | | | Date | Tue, 14 Oct 2014 18:48:55 +0800 | From | Real Name <> | Subject | why commit 3189eddbcafc cause crisv32 panic |
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hi, Guenter
http://www.gossamer-threads.com/lists/linux/kernel/2011061
>[PATCH] Revert "percpu: free percpu allocation info for uniprocessor system" > > The commit causes a hang with a crisv32 image. This may be an architecture > problem, but at least for now the revert is necessary to be able to boot a > crisv32 image.
Yes, it is a crisv32 specific issue. The crisv32 was paniced on the BUG() macro in function mark_bootmem. The call path is :
pcpu_free_alloc_info -> memblock_free_early -> free_bootmem -> mark_bootmem -> BUG()
The root source is that arch/cris/kernel/setup.c:setup_arch compute start_pfn and max_pfn from *virtual* address.
|---------- arch/cris/kernel/setup.c:setup_arch ----------------------- | start_pfn = PFN_UP(memory_start); /* usually c0000000 + kernel + romfs */ | max_pfn = PFN_DOWN((unsigned long)high_memory); /* usually c0000000 + dram size */ |---------- arch/cris/kernel/setup.c:setup_arch -----------------------
So, when memblock_free_early pass the *physical* address of ai to mark_bootmem. The first if statement of mark_bootmem become ture. And then hit the BUG() macro.
After applied the attached patch, pcpu_free_alloc_info works as expect. It had been test with your toolchain and patches you provided to me. http://server.roeck-us.net/qemu/crisv32/
cc'ed Mikael and Jesper, as they are Axis staff.
thanks diff --git a/mm/percpu.c b/mm/percpu.c index 2139e30..cbbc946 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -1097,7 +1097,12 @@ struct pcpu_alloc_info * __init pcpu_alloc_alloc_info(int nr_groups, */ void __init pcpu_free_alloc_info(struct pcpu_alloc_info *ai) { - memblock_free_early(__pa(ai), ai->__ai_size); + /* This patch is unacceptable, as it broken other arch. + * It was created to explain why commit 3189eddbcafc ("percpu: + * free percpu allocation info for uniprocessor system") cause + * crisv32 panic. PLEASE DO NOT APPLY THIS PATCH. + */ + memblock_free_early((unsigned long)(ai), ai->__ai_size); } /** @@ -1932,6 +1937,8 @@ void __init setup_per_cpu_areas(void) if (pcpu_setup_first_chunk(ai, fc) < 0) panic("Failed to initialize percpu areas."); + + pcpu_free_alloc_info(ai); } #endif /* CONFIG_SMP */ | |