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 */
