Messages in this thread | | | Date | Mon, 08 Aug 2005 12:20:57 +0200 | From | Takashi Iwai <> | Subject | Re: [PATCH 8/8] ALSA: convert kcalloc to kzalloc |
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At Sat, 06 Aug 2005 15:37:24 +0300, Pekka Enberg wrote: > > Hi, > > Dmitry Torokhov wrote: > > > Have you seen the following in include/sound/core? > > > > > > ... > > > #define kmalloc(size, flags) snd_hidden_kmalloc(size, flags) > > > #define kcalloc(n, size, flags) snd_hidden_kcalloc(n, size, flags) > > > #define kfree(obj) snd_hidden_kfree(obj) > > On Fri, 2005-08-05 at 17:10 +0100, Paulo Marques wrote: > > Arghh... I've been bitten by this before, too. > > Me too.
I understand. I would love to drop this feature if it's supported in the kernel generically.
> On Fri, 2005-08-05 at 17:10 +0100, Paulo Marques wrote: > > I really hate this "#define kmalloc" hack. It makes the code really > > unreadble, because you expect a kmalloc to be just a kmalloc... > > > > Couldn't we turn this into a generic kernel debugging option, so that it > > could be used for every kmalloc instead of just the ones from the sound > > system? > > > > If I get this right, what this code does is to track kfree's on pointers > > that were not alloc'ed with kmalloc (using a magic number) and keep > > track of all the allocations to detect leaks. > > Yes, that's what it does.
It also has a similar check for vmalloc(), but it's less important than kmalloc() (also for vmalloc, it doesn't nice since it breaks the size and the alignment).
> On Fri, 2005-08-05 at 17:10 +0100, Paulo Marques wrote: > > We already have SLAB_DEBUG. We could add a list of allocations with a > > proc interface (or something) to give an histogram of kmalloc callers / > > number of allocations not yet freed. > > > > This way, if after stopping everything related to sound there were still > > callers like "snd_xxxx" (through kallsyms) you would know there is a > > leak there. > > > > What does CONFIG_SND_DEBUG_MEMORY provide that this more generic scheme > > does not? > > I would like to make it generic too. CONFIG_SND_DEBUG_MEMORY has the > advantage of snd_memory_done() which can detect memory leaks in their > modules automatically. Therefore, to replace the ALSA magic allocator, > we would need to track which module did the allocation and add hooks to > module_exit.
Yep, this would be nice to have. The memory leak detection per module (or subsystem) helped us many times indeed.
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