[Cerowrt-devel] TFO crashes cerowrt 3.7.1-1
edumazet at google.com
Sun Jan 13 22:05:40 EST 2013
Oh well yes, this doesnt quite work on !SMP.
And this kind of bug is frequent....
See following example :
Author: Hugh Dickins <hughd at google.com>
Date: Wed Feb 8 17:13:40 2012 -0800
mm: fix UP THP spin_is_locked BUGs
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 at google.com>
Cc: Andrea Arcangeli <aarcange at redhat.com>
Cc: <stable at vger.kernel.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b3ffc21..91d3efb 100644
@@ -2083,7 +2083,7 @@ static void collect_mm_slot(struct mm_slot *mm_slot)
struct mm_struct *mm = mm_slot->mm;
+ VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
On Sun, Jan 13, 2013 at 1:39 PM, Felix Fietkau <nbd at openwrt.org> wrote:
> On 2013-01-13 7:03 PM, Eric Dumazet wrote:
> > I suspect a bug in the spin_is_locked() implementation on your arch, as
> > he socket lock should be held at this point.
> I don't think this is an arch implementation bug, this probably happens
> on all !SMP systems. See this bit from include/linux/spinlock_up.h:
> #define arch_spin_is_locked(lock) ((void)(lock), 0)
> - Felix
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