On Fri, 3 Aug 2007 00:53:44 +0200
Jesper Juhl <[EMAIL PROTECTED]> wrote:
> On Thursday 02 August 2007 10:20:47 Jesper Juhl wrote:
> > On 02/08/07, Andrew Morton <[EMAIL PROTECTED]> wrote:
> [snip]
> > > y'know, we could have a debug option which will spit warnings if someone
> > > does a !__GFP_WAIT allocation while !in_atomic() (only works if
> > > CONFIG_PREEMPT).
> > >
> > > But please, make it depend on !CONFIG_AKPM. I shudder to think about all
> > > the stuff it would pick up.
> > >
> >
> > I can try to cook up something like that tonight...
> >
>
> Ok, so I did a quick hack and I'm drowning in dmesg WARN_ON() traces
> with my usual config.
>
> This is what I added :
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 6c6d74f..e60dd9e 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -20,6 +20,7 @@
> #include <linux/mempolicy.h>
> #include <linux/ctype.h>
> #include <linux/kallsyms.h>
> +#include <linux/hardirq.h>
>
> /*
> * Lock order:
> @@ -1568,6 +1569,10 @@ static void __always_inline *slab_alloc(struct
> kmem_cache *s,
>
> void *kmem_cache_alloc(struct kmem_cache *s, gfp_t gfpflags)
> {
> +#ifdef CONFIG_PREEMPT
> + WARN_ON( !in_atomic() && !(gfpflags & __GFP_WAIT) );
> +#endif
> +
> return slab_alloc(s, gfpflags, -1, __builtin_return_address(0));
> }
> EXPORT_SYMBOL(kmem_cache_alloc);
> @@ -2370,6 +2375,10 @@ void *__kmalloc(size_t size, gfp_t flags)
> {
> struct kmem_cache *s = get_slab(size, flags);
>
> +#ifdef CONFIG_PREEMPT
> + WARN_ON( !in_atomic() && !(flags & __GFP_WAIT) );
> +#endif
> +
> if (ZERO_OR_NULL_PTR(s))
> return s;
>
>
>
> And this is what I'm getting heaps of :
>
> ...
> [ 165.128607] =======================
> [ 165.128609] WARNING: at mm/slub.c:1573 kmem_cache_alloc()
> [ 165.128611] [<c010400a>] show_trace_log_lvl+0x1a/0x30
> [ 165.128614] [<c0104cd2>] show_trace+0x12/0x20
> [ 165.128616] [<c0104cf6>] dump_stack+0x16/0x20
> [ 165.128619] [<c0175ad3>] kmem_cache_alloc+0xe3/0x110
> [ 165.128622] [<c015b10e>] mempool_alloc_slab+0xe/0x10
> [ 165.128625] [<c015b211>] mempool_alloc+0x31/0xf0
I said you would.
> So, where do we go from here?
Where I said ;) Add a new __GFP_ flag which suppresses the warning, add
that flag to known-to-be-OK callsites, such as mempool_alloc().
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