linux-kernel - Re: kmemleak issues in alsa

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Date:	Sun, 19 Jul 2009 14:07:00 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Jaswinder Singh Rajput <jaswinder@...nel.org>
Cc:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Catalin Marinas <catalin.marinas@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: kmemleak issues in alsa

At Sat, 18 Jul 2009 01:44:04 +0530,
Jaswinder Singh Rajput wrote:
> 
> I was getting these kmemleak reports when I build SND_SEQUENCER in
> kernel :
> 
> unreferenced object 0xf6b0ac00 (size 512):
>   comm "swapper", pid 1, jiffies 4294671240
>   hex dump (first 32 bytes):
>     02 00 00 00 03 4f 53 53 20 73 65 71 75 65 6e 63  .....OSS sequenc
>     65 72 00 00 00 00 00 00 00 00 00 00 00 00 00 00  er..............
>   backtrace:
>     [<c12d7d83>] kmemleak_alloc+0x25/0x49
>     [<c109350d>] kmem_cache_alloc+0x95/0x124
>     [<c12568f0>] seq_create_client1+0x1d/0x165
>     [<c1257b01>] snd_seq_create_kernel_client+0x68/0xe7
>     [<c14c966f>] snd_seq_oss_create_client+0x86/0x143
>     [<c14c958a>] alsa_seq_oss_init+0xf8/0x157
>     [<c100104f>] do_one_initcall+0x4a/0x111
>     [<c14a8608>] kernel_init+0x16b/0x1bc
>     [<c100352b>] kernel_thread_helper+0x7/0x1a
>     [<ffffffff>] 0xffffffff
> unreferenced object 0xf6b08700 (size 128):
>   comm "swapper", pid 1, jiffies 4294671240
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<c12d7d83>] kmemleak_alloc+0x25/0x49
>     [<c109350d>] kmem_cache_alloc+0x95/0x124
>     [<c12591a3>] snd_seq_pool_new+0x17/0xbe
>     [<c1256955>] seq_create_client1+0x82/0x165
>     [<c1257b01>] snd_seq_create_kernel_client+0x68/0xe7
>     [<c14c966f>] snd_seq_oss_create_client+0x86/0x143
>     [<c14c958a>] alsa_seq_oss_init+0xf8/0x157
>     [<c100104f>] do_one_initcall+0x4a/0x111
>     [<c14a8608>] kernel_init+0x16b/0x1bc
>     [<c100352b>] kernel_thread_helper+0x7/0x1a
>     [<ffffffff>] 0xffffffff
> unreferenced object 0xf6b0aa00 (size 512):
>   comm "swapper", pid 1, jiffies 4294671246
>   hex dump (first 32 bytes):
>     0f 00 00 00 00 00 00 00 52 65 63 65 69 76 65 72  ........Receiver
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<c12d7d83>] kmemleak_alloc+0x25/0x49
>     [<c109350d>] kmem_cache_alloc+0x95/0x124
>     [<c125bdf9>] snd_seq_create_port+0x4c/0x197
>     [<c1257589>] snd_seq_ioctl_create_port+0x52/0x141
>     [<c1256bb3>] snd_seq_do_ioctl+0x59/0x78
>     [<c1256c11>] snd_seq_kernel_client_ctl+0x2f/0x48
>     [<c14c96e1>] snd_seq_oss_create_client+0xf8/0x143
>     [<c14c958a>] alsa_seq_oss_init+0xf8/0x157
>     [<c100104f>] do_one_initcall+0x4a/0x111
>     [<c14a8608>] kernel_init+0x16b/0x1bc
>     [<c100352b>] kernel_thread_helper+0x7/0x1a
>     [<ffffffff>] 0xffffffff
> 
> But when I build SND_SEQUENCER as module these kmemleak issues
> disappear.
> 
> Then I noticed that issue was in ordering. 
> 
> When build in kernel flow is like this :
> 
> OSS sequencer(alsa_seq_oss_init) -> System (snd_seq_system_client_init)
> 
> When build as modules flow is like this :
> 
> System(snd_seq_system_client_init) -> OSS sequencer(alsa_seq_oss_init)
> 
> So this fixes above kmemleak issues in my case, I hope it will be
> helpful :
> 
> diff --git a/sound/core/seq/oss/seq_oss.c b/sound/core/seq/oss/seq_oss.c
> index f25e3cc..3ddf2c2 100644
> --- a/sound/core/seq/oss/seq_oss.c
> +++ b/sound/core/seq/oss/seq_oss.c
> @@ -116,7 +116,7 @@ static void __exit alsa_seq_oss_exit(void)
>  	unregister_device();
>  }
>  
> -module_init(alsa_seq_oss_init)
> +late_initcall(alsa_seq_oss_init);
>  module_exit(alsa_seq_oss_exit)

Thanks for checking this.

Another option would be to fix Makefile.  I guess simply putting the
line including sound/core/seq/oss/Makefile after the definitions of
other seq modules would do the same thing...


Takashi
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