Re: WARNING: __GFP_FS allocations with IRQs disabled (kmemcheck_alloc_shadow)

2012/7/8 Fengguang Wu [off-list ref]:

Hi Vegard,

This warning code is triggered for the attached config:

__lockdep_trace_alloc():
        /*
         * Oi! Can't be having __GFP_FS allocations with IRQs disabled.
         */
        if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
                return;

Where the irq is possibly disabled at the beginning of __slab_alloc():

        local_irq_save(flags);

Currently, in slub code, kmemcheck_alloc_shadow is always invoked with
irq_disabled.
I think that something like below is needed.

diff --git a/mm/slub.c b/mm/slub.c
index 8c691fa..5d41cad 100644
--- a/mm/slub.c
+++ b/mm/slub.c

@@ -1324,8 +1324,14 @@ static struct page *allocate_slab(struct

kmem_cache *s, gfp_t flags, int node)
                && !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) {
                int pages = 1 << oo_order(oo);

+               if (flags & __GFP_WAIT)
+                       local_irq_enable();
+
                kmemcheck_alloc_shadow(page, oo_order(oo), flags, node);

+               if (flags & __GFP_WAIT)
+                       local_irq_disable();
+
                /*
                 * Objects from caches that have a constructor don't get
                 * cleared when they're allocated, so we need to do it here.
-- 
1.7.0.4

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