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

[Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>]

On Fri, 2008-11-07 at 10:12 -0800, Fernando Lopez-Lezcano wrote:
> 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).
> > 
> > Please try the snd-virmidi driver, then we'd have a test case that does
> > not require MIDI hardware.
> > 
> > > ... 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

Nope, different this time. Maybe this one points closer to the culprit?
(BTW, snd_midi_input_event only gets called _once_, I added a few more
printk's there):

--------
Nov  7 10:34:51 host kernel: aseqdump      S [f15ce070] f7910d70     0
5341   5247
Nov  7 10:34:51 host kernel:       f3691bd4 00000086 f3691b88 f7910d70
00000001 f15ce070 f15ce304 c4852700 
Nov  7 10:34:51 host kernel:       00000002 c4852700 9a9894aa 0000002c
c484f054 00000000 fffeb4bf 00000246 
Nov  7 10:34:51 host kernel:       f35cf274 00000000 00000000 00000000
ffffffff 00000000 7fffffff f3691e98 
Nov  7 10:34:51 host kernel: Call Trace:
Nov  7 10:34:51 host kernel: [<c0643ba5>] schedule+0xbf/0xd8
Nov  7 10:34:51 host kernel: [<c0643c72>] schedule_timeout+0x17/0xbc
Nov  7 10:34:51 host kernel: [<c0496c8f>] ? __pollwait+0xad/0xb6
Nov  7 10:34:51 host kernel: [<f893cb34>] ? snd_seq_fifo_poll_wait
+0x18/0x25 [snd_seq]
Nov  7 10:34:51 host kernel: [<f8939fad>] ? snd_seq_poll+0x4d/0x9f
[snd_seq]
Nov  7 10:34:51 host kernel: [<c0495d92>] do_sys_poll+0x292/0x348
Nov  7 10:34:51 host kernel: [<c0496be2>] ? __pollwait+0x0/0xb6
Nov  7 10:34:51 host kernel: [<c0425c81>] ? default_wake_function
+0x0/0x12
Nov  7 10:34:51 host kernel: [<c0645736>] ? rt_spin_lock+0x38/0x3b
Nov  7 10:34:51 host kernel: [<c04752f7>] ? page_address+0x88/0xaa
Nov  7 10:34:51 host kernel: [<c047596d>] ? kmap_high+0x421/0x42a
Nov  7 10:34:51 host kernel: [<c04ff574>] ? radix_valid_always+0x0/0xa
Nov  7 10:34:51 host kernel: [<c046430b>] ? __rcu_read_unlock+0x6d/0x72
Nov  7 10:34:51 host kernel: [<c04699ec>] ? find_get_page+0xfa/0x120
Nov  7 10:34:51 host kernel: [<c06456c1>] ? __rt_spin_lock+0x24/0x61
Nov  7 10:34:51 host kernel: [<c0645736>] ? rt_spin_lock+0x38/0x3b
Nov  7 10:34:51 host kernel: [<c0420afc>] ? __enqueue_entity+0xe3/0xeb
Nov  7 10:34:51 host kernel: [<c041f87b>] ? task_rq_lock+0x44/0x6e
Nov  7 10:34:51 host kernel: [<c0425c76>] ? try_to_wake_up+0x212/0x21d
Nov  7 10:34:51 host kernel: [<c0425c91>] ? default_wake_function
+0x10/0x12
Nov  7 10:34:51 host kernel: [<c041ddd8>] ? __wake_up_common+0x35/0x5b
Nov  7 10:34:51 host kernel: [<c0423172>] ? __wake_up+0x28/0x32
Nov  7 10:34:51 host kernel: [<c0554f2e>] ? n_tty_receive_buf
+0xfa9/0xff7
Nov  7 10:34:51 host kernel: [<c0554f2e>] ? n_tty_receive_buf
+0xfa9/0xff7
Nov  7 10:34:51 host kernel: [<c0447cef>] ? rt_mutex_up_read+0x1b7/0x25d
Nov  7 10:34:51 host kernel: [<c0448f40>] ? rt_up_read+0x8/0xa
Nov  7 10:34:51 host kernel: [<c0647c26>] ? do_page_fault+0x45f/0x7d8
Nov  7 10:34:51 host kernel: [<c043e441>] ? hrtimer_start+0x133/0x162
Nov  7 10:34:51 host kernel: [<c04249d0>] ? hrtick_set+0x97/0xe5
Nov  7 10:34:51 host kernel: [<c06456c1>] ? __rt_spin_lock+0x24/0x61
Nov  7 10:34:51 host kernel: [<c0645736>] ? rt_spin_lock+0x38/0x3b
Nov  7 10:34:51 host kernel: [<f893cc46>] ? snd_seq_fifo_cell_out
+0x47/0xee [snd_seq]
Nov  7 10:34:51 host kernel: [<c0425c81>] ? default_wake_function
+0x0/0x12
Nov  7 10:34:51 host kernel: [<f893a041>] ? snd_seq_read+0x0/0x1d8
[snd_seq]
Nov  7 10:34:51 host kernel: [<f893a11e>] ? snd_seq_read+0xdd/0x1d8
[snd_seq]
Nov  7 10:34:51 host kernel: [<c04d73d3>] ? security_file_permission
+0xf/0x11
Nov  7 10:34:51 host kernel: [<c045e231>] ? audit_syscall_entry
+0xf9/0x123
Nov  7 10:34:51 host kernel: [<c049606a>] sys_poll+0x3a/0x6a
Nov  7 10:34:51 host kernel: [<c0404be6>] syscall_call+0x7/0xb
Nov  7 10:34:51 host kernel: =======================
--------

-- Fernando