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SubjectRe: kernel BUG at mm/memory.c:1228!
On Wed, 6 Jun 2012, Dave Jones wrote:

> I hit this in overnight testing..
>
> ------------[ cut here ]------------
> kernel BUG at mm/memory.c:1228!

Looks like a duplicate of the "mm: kernel BUG at mm/memory.c:1230" thread
at http://marc.info/?t=133788420400003
Andrea suggested adding a printk of addr, end, vma->vm_start, and
vma->vm_end to debug it.

Since it's been reported a few different times, perhaps this should be
merged?


mm, thp: print useful information when mmap_sem is unlocked in zap_pmd_range

Andrea asked for addr, end, vma->vm_start, and vma->vm_end to be emitted
when !rwsem_is_locked(&tlb->mm->mmap_sem). Otherwise, debugging the
underlying issue is more difficult.

Signed-off-by: David Rientjes <rientjes@google.com>
---
mm/memory.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/mm/memory.c b/mm/memory.c
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1225,7 +1225,15 @@ static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
next = pmd_addr_end(addr, end);
if (pmd_trans_huge(*pmd)) {
if (next - addr != HPAGE_PMD_SIZE) {
- VM_BUG_ON(!rwsem_is_locked(&tlb->mm->mmap_sem));
+#ifdef CONFIG_DEBUG_VM
+ if (!rwsem_is_locked(&tlb->mm->mmap_sem)) {
+ pr_err("%s: mmap_sem is unlocked! addr=%lu end=%lu vma->vm_start=%lu vma->vm_end=%lu\n",
+ __func__, addr, end,
+ vma->vm_start,
+ vma->vm_end);
+ BUG();
+ }
+#endif
split_huge_page_pmd(vma->vm_mm, pmd);
} else if (zap_huge_pmd(tlb, vma, pmd, addr))
goto next;

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