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SubjectRe: boot panic after oops from sysfs_new_dirent
Meelis Roos wrote:
>> Ummm.... one more question. Is cpu0 missing? Can you please post the
>> output of "cat /proc/cpuinfo"?
>
> Yes, there's no CPU numbered 0, the numbers come from hardware slots on
> backplane.

Aha... Does the following patch fix the problem?

diff --git a/mm/percpu.c b/mm/percpu.c
index 5fe3784..3311c89 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -197,7 +197,12 @@ static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
static bool pcpu_chunk_page_occupied(struct pcpu_chunk *chunk,
int page_idx)
{
- return *pcpu_chunk_pagep(chunk, 0, page_idx) != NULL;
+ /*
+ * Any possible cpu id can be used here, so there's no need to
+ * worry about preemption or cpu hotplug.
+ */
+ return *pcpu_chunk_pagep(chunk, raw_smp_processor_id(),
+ page_idx) != NULL;
}

/* set the pointer to a chunk in a page struct */
@@ -297,6 +302,14 @@ static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
return pcpu_first_chunk;
}

+ /*
+ * The address is relative to unit0 which might be unused and
+ * thus unmapped. Offset the address to the unit space of the
+ * current processor before looking it up in the vmalloc
+ * space. Note that any possible cpu id can be used here, so
+ * there's no need to worry about preemption or cpu hotplug.
+ */
+ addr += raw_smp_processor_id() * pcpu_unit_size;
return pcpu_get_page_chunk(vmalloc_to_page(addr));
}

--
tejun

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