[alsa-devel] 2.6.26.[6|7]-rt11, alsa rawmidi, seq hang

[Fernando Lopez-Lezcano]

On Fri, 2008-11-07 at 10:12 +0100, Clemens Ladisch wrote:
> Fernando Lopez-Lezcano wrote:
> > I'm seeing a realtime patch related hard hang in the kernel alsa
> > subsystem (MIDI input/output). In a nutshell:
> >
> > - alsa rawmidi works (ie: "rawmidi -v -i hw:0" outputs a stream of
> > messages when pointed to a midi capable card that has an external
> > keyboard connected).
> >
> > - the alsa sequencer interface works (ie: aplaymidi connected to
> > aseqdump transfers data just fine).
> >
> > - BOTH combined do NOT work (ie: use aconnect to connect the port that
> > corresponds to the external midi interface to aseqdump: aseqdump hangs
> > forever after transferring the first message and the only way out is a
> > reboot).
> 
> > ... including the output of a "echo t >/proc/sysrq-trigger" that
> > should show where aseqdump currently hangs (or so I think).
> 
> It hangs in tasklet_kill(), which gets called while it tries to close
> the rawmidi port.
> 
> The rawmidi framework uses this tasklet to notify the sequencer that new
> MIDI data is available.  The handler function is
> snd_rawmidi_input_event_tasklet() in sound/core/rawmidi.c; the sequencer
> callback that gets called from there is snd_midi_input_event() in
> core/seq/seq_midi.c.
> 
> You say that the first event gets delivered, so it might be possible
> that the tasklet never finishes executing.  Please check whether the
> call to snd_seq_kernel_client_dispatch() in snd_midi_input_event()
> ever returns.

Going back to this in the hope of a bit more data helping solve the
problem...

I don't understand what is going on (of course! :-)

Cards look like this:

$ cat /proc/asound/cards
 0 [Gina3G         ]: Echo_Echo3G - Gina3G
                      Gina3G rev.0 (DSP56361) at 0xfeb00000 irq 18
 1 [Intel          ]: HDA-Intel - HDA Intel
                      HDA Intel at 0xfe7f8000 irq 22
 2 [PCR            ]: USB-Audio - PCR
                      EDIROL PCR at usb-0000:00:1d.0-1, full speed

Here's what I do:
  - start aseqdump
  - aconnect 16:0 128:0
  - aseqdump receives one midi message (one byte active sensing msg)
  - aseqdump hangs forever (reboot needed)

This is what dmesg prints (patch attached which shows where the printk's
are located in the source for rawmidi.c and seq_midi.c):

== this starts happening as soon as I run aconnect:
rawmidi: before input ops trigger
rawmidi: after input ops trigger
rawmidi: before input ops trigger
rawmidi: after input ops trigger
== hmmm, after it is actually subscribed?
rawmidi: before receive spinlock
rawmidi: after receive spinlock
rawmidi: about to run receive tasklet
rawmidi: run receive tasklet
rawmidi: before receive spin unlock
rawmidi: after receive spin unlock
rawmidi: about to run input tasklet
seq: snd_midi_input_event called
seq: seq_midi_input_event loop begin
rawmidi: before input ops trigger
rawmidi: after input ops trigger
seq: snd_seq_kernel_client_dispatch called
seq: snd_seq_kernel_client_dispatch returned
seq: snd_midi_input_event exiting
rawmidi: after running input tasklet
rawmidi: before receive spinlock
rawmidi: after receive spinlock
rawmidi: about to run receive tasklet
rawmidi: run receive tasklet
rawmidi: before receive spin unlock
rawmidi: after receive spin unlock
rawmidi: before receive spinlock
rawmidi: after receive spinlock
rawmidi: about to run receive tasklet
rawmidi: run receive tasklet
rawmidi: before receive spin unlock
rawmidi: after receive spin unlock
rawmidi: before receive spinlock
rawmidi: after receive spinlock
rawmidi: about to run receive tasklet
rawmidi: run receive tasklet
rawmidi: before receive spin unlock
rawmidi: after receive spin unlock
rawmidi: before receive spinlock
rawmidi: after receive spinlock

So, snd_midi_input_event runs once but never gets called back. 

Something else is deadlocking, what can it be? (ie: where can I put more
printk's to try to see what is going on??)

This is where I think aseqdujmp hangs:

Nov 13 11:36:53 host kernel: =======================
Nov 13 11:36:53 host kernel: aseqdump      S [f3505170] f7960f30     0
5580   5515
Nov 13 11:36:53 host kernel:       f567bbd4 00200082 00000001 f7960f30
00200246 f3505170 f3505404 c485d700 
Nov 13 11:36:53 host kernel:       00000003 c485d700 9a5d89b4 000000bc
f567bba4 f567bba4 0007c8c8 00200246 
Nov 13 11:36:53 host kernel:       f35a7af4 00000000 00000000 00000000
ffffffff 00000000 7fffffff f567be98 
Nov 13 11:36:53 host kernel: Call Trace:
Nov 13 11:36:53 host kernel: [<c0643ba5>] schedule+0xbf/0xd8
Nov 13 11:36:53 host kernel: [<c0643c72>] schedule_timeout+0x17/0xbc
Nov 13 11:36:53 host kernel: [<c0496c8f>] ? __pollwait+0xad/0xb6
Nov 13 11:36:53 host kernel: [<f8968b34>] ? snd_seq_fifo_poll_wait
+0x18/0x25 [snd_seq]
Nov 13 11:36:53 host kernel: [<f8965fad>] ? snd_seq_poll+0x4d/0x9f
[snd_seq]
Nov 13 11:36:53 host kernel: [<c0495d92>] do_sys_poll+0x292/0x348
Nov 13 11:36:53 host kernel: [<c0496be2>] ? __pollwait+0x0/0xb6
Nov 13 11:36:53 host kernel: [<c0425c81>] ? default_wake_function
+0x0/0x12
Nov 13 11:36:53 host kernel: [<c0645736>] ? rt_spin_lock+0x38/0x3b
Nov 13 11:36:53 host kernel: [<c04752f7>] ? page_address+0x88/0xaa
Nov 13 11:36:53 host kernel: [<c047596d>] ? kmap_high+0x421/0x42a
Nov 13 11:36:53 host kernel: [<c04ff574>] ? radix_valid_always+0x0/0xa
Nov 13 11:36:53 host kernel: [<c046430b>] ? __rcu_read_unlock+0x6d/0x72
Nov 13 11:36:53 host kernel: [<c04699ec>] ? find_get_page+0xfa/0x120
Nov 13 11:36:53 host kernel: [<c06456c1>] ? __rt_spin_lock+0x24/0x61
Nov 13 11:36:53 host kernel: [<c0645736>] ? rt_spin_lock+0x38/0x3b
Nov 13 11:36:53 host kernel: [<c0420afc>] ? __enqueue_entity+0xe3/0xeb
Nov 13 11:36:53 host kernel: [<c041f87b>] ? task_rq_lock+0x44/0x6e
Nov 13 11:36:53 host kernel: [<c0425c76>] ? try_to_wake_up+0x212/0x21d
Nov 13 11:36:53 host kernel: [<c0425c91>] ? default_wake_function
+0x10/0x12
Nov 13 11:36:53 host kernel: [<c041ddd8>] ? __wake_up_common+0x35/0x5b
Nov 13 11:36:53 host kernel: [<c0423172>] ? __wake_up+0x28/0x32
Nov 13 11:36:53 host kernel: [<c0554f2e>] ? n_tty_receive_buf
+0xfa9/0xff7
Nov 13 11:36:53 host kernel: [<c0554f2e>] ? n_tty_receive_buf
+0xfa9/0xff7
Nov 13 11:36:53 host kernel: [<c0447cef>] ? rt_mutex_up_read+0x1b7/0x25d
Nov 13 11:36:53 host kernel: [<c0448f40>] ? rt_up_read+0x8/0xa
Nov 13 11:36:53 host kernel: [<c0647c26>] ? do_page_fault+0x45f/0x7d8
Nov 13 11:36:53 host kernel: [<c0502f6c>] ? copy_to_user+0x36/0x106
Nov 13 11:36:53 host kernel: [<c06456c1>] ? __rt_spin_lock+0x24/0x61
Nov 13 11:36:53 host kernel: [<c0645736>] ? rt_spin_lock+0x38/0x3b
Nov 13 11:36:53 host kernel: [<f8968c46>] ? snd_seq_fifo_cell_out
+0x47/0xee [snd_seq]
Nov 13 11:36:53 host kernel: [<c0425c81>] ? default_wake_function
+0x0/0x12
Nov 13 11:36:53 host kernel: [<f8966041>] ? snd_seq_read+0x0/0x1d8
[snd_seq]
Nov 13 11:36:53 host kernel: [<f896611e>] ? snd_seq_read+0xdd/0x1d8
[snd_seq]
Nov 13 11:36:53 host kernel: [<c04d73d3>] ? security_file_permission
+0xf/0x11
Nov 13 11:36:53 host kernel: [<c045e231>] ? audit_syscall_entry
+0xf9/0x123
Nov 13 11:36:53 host kernel: [<c049606a>] sys_poll+0x3a/0x6a
Nov 13 11:36:53 host kernel: [<c0404be6>] syscall_call+0x7/0xb
Nov 13 11:36:53 host kernel: =======================

Looks like it is a poll...

Then, when I try to actually kill aseqdump I get this in the log:

Nov 13 11:39:02 host kernel: rawmidi: about to kill input tasklet

And the trace:

Nov 13 11:39:13 host kernel: aseqdump      D [f3505170] f786c0b0     0
5580   5515
Nov 13 11:39:13 host kernel:       f567be0c 00200082 00000000 f786c0b0
00200246 f3505170 f3505404 c483c700 
Nov 13 11:39:13 host kernel:       00000000 c483c700 5618b41d 00000121
f567bdf4 000e6262 f567bdf4 c04320f3 
Nov 13 11:39:13 host kernel:       f567be1c f567be1c f567be14 c0432918
000e6263 000e6263 f567be1c f567be48 
Nov 13 11:39:13 host kernel: Call Trace:
Nov 13 11:39:13 host kernel: [<c04320f3>] ? internal_add_timer+0x88/0x8c
Nov 13 11:39:13 host kernel: [<c0432918>] ? __mod_timer+0xc8/0xd3
Nov 13 11:39:13 host kernel: [<c0643ba5>] schedule+0xbf/0xd8
Nov 13 11:39:13 host kernel: [<c0643cf8>] schedule_timeout+0x9d/0xbc
Nov 13 11:39:13 host kernel: [<c0431da2>] ? process_timeout+0x0/0xa
Nov 13 11:39:13 host kernel: [<c0643cf3>] ? schedule_timeout+0x98/0xbc
Nov 13 11:39:13 host kernel: [<c0643d2c>]
schedule_timeout_uninterruptible+0x15/0x17
Nov 13 11:39:13 host kernel: [<c0432a1b>] msleep+0x10/0x16
Nov 13 11:39:13 host kernel: [<c042eaef>] tasklet_kill+0x2e/0x58
Nov 13 11:39:13 host kernel: [<f89bb755>] snd_rawmidi_input_trigger
+0x31/0x44 [snd_rawmidi]
Nov 13 11:39:13 host kernel: [<f89bceeb>] snd_rawmidi_kernel_release
+0x37/0x105 [snd_rawmidi]
Nov 13 11:39:13 host kernel: [<f8f28633>] midisynth_unsubscribe+0xb/0xd
[snd_seq_midi]
Nov 13 11:39:13 host kernel: [<f8969cb9>] unsubscribe_port+0x3c/0x71
[snd_seq]
Nov 13 11:39:13 host kernel: [<f896a510>] clear_subscriber_list
+0xae/0xdb [snd_seq]
Nov 13 11:39:13 host kernel: [<f896a57e>] port_delete+0x41/0x65
[snd_seq]
Nov 13 11:39:13 host kernel: [<f896a63c>] snd_seq_delete_all_ports
+0x9a/0xba [snd_seq]
Nov 13 11:39:13 host kernel: [<f8965175>] seq_free_client1+0xb/0x90
[snd_seq]
Nov 13 11:39:13 host kernel: [<f8965232>] seq_free_client+0x38/0x6f
[snd_seq]
Nov 13 11:39:13 host kernel: [<f896527e>] snd_seq_release+0x15/0x35
[snd_seq]
Nov 13 11:39:13 host kernel: [<c048b5a2>] __fput+0xae/0x158
Nov 13 11:39:13 host kernel: [<c048b663>] fput+0x17/0x19
Nov 13 11:39:13 host kernel: [<c0488b95>] filp_close+0x50/0x5a
Nov 13 11:39:13 host kernel: [<c0488c12>] sys_close+0x73/0xad
Nov 13 11:39:13 host kernel: [<c0404be6>] syscall_call+0x7/0xb
Nov 13 11:39:13 host kernel: =======================

-- Fernando

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