* [PATCH] mm: fix UP THP spin_is_locked BUGs
@ 2012-02-08 0:00 Hugh Dickins
2012-02-08 0:12 ` Andrew Morton
0 siblings, 1 reply; 4+ messages in thread
From: Hugh Dickins @ 2012-02-08 0:00 UTC (permalink / raw)
To: Andrew Morton; +Cc: Andrea Arcangeli, linux-mm
Fix CONFIG_TRANSPARENT_HUGEPAGE=y CONFIG_SMP=n CONFIG_DEBUG_VM=y
CONFIG_DEBUG_SPINLOCK=n kernel: spin_is_locked() is then always false,
and so triggers some BUGs in Transparent HugePage codepaths.
asm-generic/bug.h mentions this problem, and provides a WARN_ON_SMP(x);
but being too lazy to add VM_BUG_ON_SMP, BUG_ON_SMP, WARN_ON_SMP_ONCE,
VM_WARN_ON_SMP_ONCE, just test NR_CPUS != 1 in the existing VM_BUG_ONs.
Signed-off-by: Hugh Dickins <hughd@google.com>
---
mm/huge_memory.c | 4 ++--
mm/swap.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
--- 3.3-rc2/mm/huge_memory.c 2012-01-20 08:42:35.304020840 -0800
+++ linux/mm/huge_memory.c 2012-02-07 15:37:18.581666053 -0800
@@ -2083,7 +2083,7 @@ static void collect_mm_slot(struct mm_sl
{
struct mm_struct *mm = mm_slot->mm;
- VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
+ VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
if (khugepaged_test_exit(mm)) {
/* free mm_slot */
@@ -2113,7 +2113,7 @@ static unsigned int khugepaged_scan_mm_s
int progress = 0;
VM_BUG_ON(!pages);
- VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
+ VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
if (khugepaged_scan.mm_slot)
mm_slot = khugepaged_scan.mm_slot;
--- 3.3-rc2/mm/swap.c 2012-01-20 08:42:35.324020840 -0800
+++ linux/mm/swap.c 2012-02-07 15:37:18.581666053 -0800
@@ -659,7 +659,7 @@ void lru_add_page_tail(struct zone* zone
VM_BUG_ON(!PageHead(page));
VM_BUG_ON(PageCompound(page_tail));
VM_BUG_ON(PageLRU(page_tail));
- VM_BUG_ON(!spin_is_locked(&zone->lru_lock));
+ VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&zone->lru_lock));
SetPageLRU(page_tail);
--
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] mm: fix UP THP spin_is_locked BUGs
2012-02-08 0:00 [PATCH] mm: fix UP THP spin_is_locked BUGs Hugh Dickins
@ 2012-02-08 0:12 ` Andrew Morton
2012-02-08 0:33 ` Hugh Dickins
0 siblings, 1 reply; 4+ messages in thread
From: Andrew Morton @ 2012-02-08 0:12 UTC (permalink / raw)
To: Hugh Dickins; +Cc: Andrea Arcangeli, linux-mm
On Tue, 7 Feb 2012 16:00:46 -0800 (PST)
Hugh Dickins <hughd@google.com> wrote:
> Fix CONFIG_TRANSPARENT_HUGEPAGE=y CONFIG_SMP=n CONFIG_DEBUG_VM=y
> CONFIG_DEBUG_SPINLOCK=n kernel: spin_is_locked() is then always false,
> and so triggers some BUGs in Transparent HugePage codepaths.
>
> asm-generic/bug.h mentions this problem, and provides a WARN_ON_SMP(x);
> but being too lazy to add VM_BUG_ON_SMP, BUG_ON_SMP, WARN_ON_SMP_ONCE,
> VM_WARN_ON_SMP_ONCE, just test NR_CPUS != 1 in the existing VM_BUG_ONs.
>
> Signed-off-by: Hugh Dickins <hughd@google.com>
> ---
>
> mm/huge_memory.c | 4 ++--
> mm/swap.c | 2 +-
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> --- 3.3-rc2/mm/huge_memory.c 2012-01-20 08:42:35.304020840 -0800
> +++ linux/mm/huge_memory.c 2012-02-07 15:37:18.581666053 -0800
> @@ -2083,7 +2083,7 @@ static void collect_mm_slot(struct mm_sl
> {
> struct mm_struct *mm = mm_slot->mm;
>
> - VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
> + VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
We do have assert_spin_locked(), but I couldn't see any way of using it
while observing these laziness constraints ;)
Should we patch -stable too?
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] mm: fix UP THP spin_is_locked BUGs
2012-02-08 0:12 ` Andrew Morton
@ 2012-02-08 0:33 ` Hugh Dickins
2012-02-08 2:35 ` Andrew Morton
0 siblings, 1 reply; 4+ messages in thread
From: Hugh Dickins @ 2012-02-08 0:33 UTC (permalink / raw)
To: Andrew Morton; +Cc: Andrea Arcangeli, linux-mm
On Tue, 7 Feb 2012, Andrew Morton wrote:
> On Tue, 7 Feb 2012 16:00:46 -0800 (PST)
> Hugh Dickins <hughd@google.com> wrote:
>
> > +++ linux/mm/huge_memory.c 2012-02-07 15:37:18.581666053 -0800
> > @@ -2083,7 +2083,7 @@ static void collect_mm_slot(struct mm_sl
> > {
> > struct mm_struct *mm = mm_slot->mm;
> >
> > - VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
> > + VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
>
> We do have assert_spin_locked(), but I couldn't see any way of using it
> while observing these laziness constraints ;)
;) I didn't know about assert_spin_locked(). Hmm, fs/dcache.c seems
to be using that successfully. We could forget about the VM_ part of
it and respin the patch with assert_spin_locked(). I don't really
mind either way: but happy to let laziness win the day - I'm back
on an SMP kernel by now anyway.
>
> Should we patch -stable too?
People seem to have survived very well without it so far, I think
it's an unusual config combination, and quickly obvious if anyone
hits it. But I've no objection if you think it deserves -stable.
Hugh
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] mm: fix UP THP spin_is_locked BUGs
2012-02-08 0:33 ` Hugh Dickins
@ 2012-02-08 2:35 ` Andrew Morton
0 siblings, 0 replies; 4+ messages in thread
From: Andrew Morton @ 2012-02-08 2:35 UTC (permalink / raw)
To: Hugh Dickins; +Cc: Andrea Arcangeli, linux-mm
On Tue, 7 Feb 2012 16:33:18 -0800 (PST) Hugh Dickins <hughd@google.com> wrote:
> > Should we patch -stable too?
>
> People seem to have survived very well without it so far, I think
> it's an unusual config combination, and quickly obvious if anyone
> hits it. But I've no objection if you think it deserves -stable.
We may as well, I guess. Runtime BUG() is rather unpleasant.
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^ permalink raw reply [flat|nested] 4+ messages in thread
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2012-02-08 0:00 [PATCH] mm: fix UP THP spin_is_locked BUGs Hugh Dickins
2012-02-08 0:12 ` Andrew Morton
2012-02-08 0:33 ` Hugh Dickins
2012-02-08 2:35 ` Andrew Morton
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