Re: Rawmidi and CONFIG_DEBUG_SPINLOCK_SLEEP

[Thomas Charbonnel <thomas@undata.org>]

Jaroslav Kysela a écrit :
> On Thu, 29 Jan 2004, Thomas Charbonnel wrote:
> 
> 
>>Hi,
>>
>>I noticed this problem today using midi on my setup (alsa 1.0.1, kernel 
>>2.6.1 with CONFIG_DEBUG_SPINLOCK_SLEEP) :
>>
>>Debug: sleeping function called from invalid context at 
>>include/asm/uaccess.h:473
>>in_atomic():1, irqs_disabled():1
>>Call Trace:
>>  [<c012139c>] __might_sleep+0xac/0xe0
>>  [<c010b170>] handle_signal+0xd0/0x140
>>  [<c03955ef>] snd_rawmidi_kernel_read1+0x10f/0x170
>>  [<c03957e7>] snd_rawmidi_read+0x147/0x1b0
>>  [<c01131cf>] restore_i387_fxsave+0x8f/0xa0
>>  [<c015b2f3>] vfs_read+0xd3/0x140
>>  [<c015b59f>] sys_read+0x3f/0x60
>>  [<c010b4bb>] syscall_call+0x7/0xb
>>
>>I'm sorry I didn't check if this was fixed in 1.0.2, but though it was 
>>worth mentioning. This caused regular (~ 1/second) dropouts in pd while 
>>using midi.
> 
> 
> I'm not sure, but it looks like kernel problem. We don't call
> handle_signal() function from snd_rawmidi_kernel_read1() - you may check
> this function - scheduling is not involved. I wonder why this function is
> called from in the spinlock context.
> 
> Please, report this problem to LKML or try the latest 2.6 kernel.
> 
> 						Jaroslav
> 

Hi Jaroslav,

Doing some more tests I got also this message :

Debug: sleeping function called from invalid context at
include/asm/uaccess.h:498
in_atomic():1, irqs_disabled():1
Call Trace:
  [<c012139c>] __might_sleep+0xac/0xe0
  [<c0395c2d>] snd_rawmidi_kernel_write1+0x16d/0x200
  [<c0395ea4>] snd_rawmidi_write+0x1b4/0x300
  [<c010b2c1>] do_signal+0xe1/0xf0
  [<c01131cf>] restore_i387_fxsave+0x8f/0xa0
  [<c015b4f3>] vfs_write+0xd3/0x140
  [<c015b5ff>] sys_write+0x3f/0x60
  [<c010b4bb>] syscall_call+0x7/0xb

The kernel functions pointed to in include/asm/usaccess.h are
copy_to_user and copy_from_user. They are indeed called from a spinlock
context from both snd_rawmidi_kernel_write1 and
snd_rawmidi_kernel_read1, and are flagged might_sleep. The strange thing
is that they were already flagged might_sleep in 2.6.0, which I believe
I compiled with CONFIG_DEBUG_SPINLOCK_SLEEP also, and I can't remember
having the problem. On the other hand I only checked dmesg here because
I could hear audio dropouts. Maybe the might_sleep detection code has
been changed and is responsible for the dropouts ?

Thomas





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