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SubjectRe: kmemleak issues in alsa
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Hello Takashi,

On Sun, 2009-07-19 at 14:07 +0200, Takashi Iwai wrote:
> 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...

Yes, this also fixes the ordering and memory leak when build
SND_SEQUENCER in kernel and is equivalent to :

1. insmod sound/core/seq/snd-seq-device.ko
2. insmod sound/core/seq/snd-seq.ko
3. insmod sound/core/seq/snd-seq-midi-event.ko
4. insmod sound/core/seq/oss/snd-seq-oss.ko

diff --git a/sound/core/seq/Makefile b/sound/core/seq/Makefile
index 1bcb360..941f64a 100644
--- a/sound/core/seq/Makefile
+++ b/sound/core/seq/Makefile
@@ -3,10 +3,6 @@
# Copyright (c) 1999 by Jaroslav Kysela <perex@perex.cz>
#

-ifeq ($(CONFIG_SND_SEQUENCER_OSS),y)
- obj-$(CONFIG_SND_SEQUENCER) += oss/
-endif
-
snd-seq-device-objs := seq_device.o
snd-seq-objs := seq.o seq_lock.o seq_clientmgr.o seq_memory.o seq_queue.o \
seq_fifo.o seq_prioq.o seq_timer.o \
@@ -19,7 +15,8 @@ snd-seq-virmidi-objs := seq_virmidi.o

obj-$(CONFIG_SND_SEQUENCER) += snd-seq.o snd-seq-device.o
ifeq ($(CONFIG_SND_SEQUENCER_OSS),y)
-obj-$(CONFIG_SND_SEQUENCER) += snd-seq-midi-event.o
+ obj-$(CONFIG_SND_SEQUENCER) += snd-seq-midi-event.o
+ obj-$(CONFIG_SND_SEQUENCER) += oss/
endif
obj-$(CONFIG_SND_SEQ_DUMMY) += snd-seq-dummy.o

--
JSR


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