On Sat, Nov 17, 2007 at 07:09:46PM +0100, Ingo Molnar wrote:
>
> * Torsten Kaiser <[email protected]> wrote:
>
> > Sadly lockdep does not work for me, as it gets turned off early:
> > [ 39.851594] ---------------------------------
> > [ 39.855963] inconsistent {softirq-on-W} -> {in-softirq-W} usage.
> > [ 39.861981] swapper/0 [HC0[0]:SC1[1]:HE0:SE0] takes:
> > [ 39.866963] (&n->list_lock){-+..}, at: [<ffffffff802935c1>]
>
> hey, that means it found a bug - which is not sad at all :-)
---
Subject: lockdep: slub: annotate boot time node->list_lock usage
inconsistent {softirq-on-W} -> {in-softirq-W} usage.
swapper/0 [HC0[0]:SC1[1]:HE0:SE0] takes:
(&n->list_lock){-+..}, at: [<ffffffff802935c1>] add_partial+0x31/0xa0
{softirq-on-W} state was registered at:
[<ffffffff80259fb8>] __lock_acquire+0x3e8/0x1140
[<ffffffff80259838>] debug_check_no_locks_freed+0x188/0x1a0
[<ffffffff8025ad65>] lock_acquire+0x55/0x70
[<ffffffff802935c1>] add_partial+0x31/0xa0
[<ffffffff805c76de>] _spin_lock+0x1e/0x30
[<ffffffff802935c1>] add_partial+0x31/0xa0
[<ffffffff80296f9c>] kmem_cache_open+0x1cc/0x330
[<ffffffff805c7984>] _spin_unlock_irq+0x24/0x30
[<ffffffff802974f4>] create_kmalloc_cache+0x64/0xf0
[<ffffffff80295640>] init_alloc_cpu_cpu+0x70/0x90
[<ffffffff8080ada5>] kmem_cache_init+0x65/0x1d0
[<ffffffff807f1b4e>] start_kernel+0x23e/0x350
[<ffffffff807f112d>] _sinittext+0x12d/0x140
[<ffffffffffffffff>] 0xffffffffffffffff
Signed-off-by: Peter Zijlstra <[email protected]>
CC: Christoph Lameter <[email protected]>
CC: Kamalesh Babulal <[email protected]>
---
mm/slub.c | 8 ++++++++
1 file changed, 8 insertions(+)
Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c
+++ linux-2.6/mm/slub.c
@@ -2155,6 +2155,7 @@ static struct kmem_cache_node *early_kme
{
struct page *page;
struct kmem_cache_node *n;
+ unsigned long flags;
BUG_ON(kmalloc_caches->size < sizeof(struct kmem_cache_node));
@@ -2179,7 +2180,14 @@ static struct kmem_cache_node *early_kme
#endif
init_kmem_cache_node(n);
atomic_long_inc(&n->nr_slabs);
+ /*
+ * lockdep requires consistent irq usage for each lock
+ * so even though there cannot be a race this early in
+ * the boot sequence, we still disable irqs.
+ */
+ local_irq_save(flags);
add_partial(kmalloc_caches, page, 0);
+ local_irq_restore(flags);
return n;
}
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