linux-kernel - Re: [PATCH 01/15] kmemleak: Add the base support

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Message-ID: <84144f020811302249i7587662ewa621d0a81f5426a2@mail.gmail.com>
Date:	Mon, 1 Dec 2008 08:49:38 +0200
From:	"Pekka Enberg" <penberg@...helsinki.fi>
To:	"Yasunori Goto" <y-goto@...fujitsu.com>
Cc:	"Catalin Marinas" <catalin.marinas@....com>,
	linux-kernel@...r.kernel.org, "Ingo Molnar" <mingo@...e.hu>
Subject: Re: [PATCH 01/15] kmemleak: Add the base support

Hi!

On Mon, Dec 1, 2008 at 7:39 AM, Yasunori Goto <y-goto@...fujitsu.com> wrote:
>> +/*
>> + * Insert a pointer into the pointer hash table.
>> + */
>> +static inline void create_object(unsigned long ptr, size_t size, int ref_count)
>> +{
>> +     unsigned long flags;
>> +     struct memleak_object *object;
>> +     struct prio_tree_node *node;
>> +     struct stack_trace trace;
>> +
>> +     object = kmem_cache_alloc(object_cache, GFP_ATOMIC);
>> +     if (!object)
>> +             panic("kmemleak: cannot allocate a memleak_object structure\n");
>
> IIRC, GFP_ATOMIC allocation sometimes fails. (ex. when page cache occupies all
> area). It seems to be easy to panic. Is it intended?

Yup, GFP_ATOMIC can fail as can any memory allocation on out-of-memory
conditions unless you specify GFP_NOFAIL which will either succeed or
lock up the box. I think you can just WARN_ON() here? However, it's
probably safer to pass gfp flags from the callers here; otherwise we
end up doing tons of GFP_ATOMIC allocations which is not healthy in
general.

Also, I see some other BUG_ON() calls in the code which probably
should be converted to WARN_ON() as well.
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