> >
> > could you get a tasklist-dump? It's either SysRq-T, or:
> >
> > echo t > /proc/sysrq-trigger
> >
> > that should dump all tasks and their backtraces -
> including the hung
> > rosegardensequencer task.
>
> I'll try to do that tomorrow.
>
> In the meanwhile I think this might be the same problem
> that was solved
> in -rt20? (building it as I type). I have been trying to
> catch up to the
> subset of lkml that I manage to read and found some
> reports that
> apparently point to similar problems with the alsa
> sequencer (Rui, in
> particular, and then Karsten's post in this thread).
ALSA Midi sequencer uses tasklets. there are 2 kinds of
them: lo and hi.
In rt-18 PREEMPT-RT, tasklet_hi_schedule() didn't work,
'cause it woke up tasklet_lo's thread.
Thats what my patch fixed.
Before finding the solution, i reduced my testcase
to a simple "aconnect -d" call:
aconnect sends a midi-reset to the client to disconnect via
tasklet_hi then. subsequently aconnect wants to finish, and
cannot: it has to wait for tasklet_hi cleanup, which
doesn't happen, 'cause the wrong thread had been triggered.
Find the corresponding sysrq-t excerpt attached.
Karsten
___________________________________________________________
Telefonate ohne weitere Kosten vom PC zum PC: http://messenger.yahoo.de[ 998.876000] aconnect [f5867010]R C013CF4C [on rq #0] 0 2708 2272 (NOTLB)
[ 998.876000] f3ca1d1c f5867010 c0452ee0 c013cf4c f3ca1000 00000000 f5867148 c0494740
[ 998.876000] f3ca1d08 f5867010 8ec9c300 000000e8 003d0900 00000000 f3ca1000 0002aa75
[ 998.876000] 00000000 f3ca1d44 c034a6e5 c01279b9 c0494740 f3ca1d58 0002aa73 60000000
[ 998.876000] Call Trace:
[ 998.876000] [<c034a6e5>] schedule+0xa5/0x140 (40)
[ 998.876000] [<c034b0cc>] schedule_timeout+0x4c/0xc0 (52)
[ 998.876000] [<c034b17a>] schedule_timeout_uninterruptible+0x1a/0x20 (8)
[ 998.876000] [<c0128bd8>] msleep+0x28/0x40 (12)
[ 998.876000] [<c0123ddc>] tasklet_kill+0x3c/0x70 (16)
[ 998.876000] [<f88372a3>] snd_rawmidi_drop_output+0x43/0x90 [snd_rawmidi] (32)
[ 998.876000] [<f8837372>] snd_rawmidi_drain_output+0x82/0x180 [snd_rawmidi] (68)
[ 998.876000] [<f8a4c5a7>] midisynth_unuse+0x37/0x80 [snd_seq_midi] (32)
[ 998.876000] [<f8aafb3e>] unsubscribe_port+0x4e/0x100 [snd_seq] (36)
[ 998.876000] [<f8ab0004>] snd_seq_port_disconnect+0x134/0x180 [snd_seq] (60)
[ 998.876000] [<f8aa9eb6>] snd_seq_ioctl_unsubscribe_port+0xe6/0x140 [snd_seq] (132)
[ 998.876000] [<f8aaaf9a>] snd_seq_do_ioctl+0x5a/0xd0 [snd_seq] (36)
[ 998.876000] [<f8aab039>] snd_seq_ioctl+0x29/0x60 [snd_seq] (24)
[ 998.876000] [<c01838a8>] do_ioctl+0x38/0xa0 (36)
[ 998.876000] [<c0183ad0>] vfs_ioctl+0x60/0x200 (40)
[ 998.876000] [<c0183cea>] sys_ioctl+0x7a/0x90 (40)
[ 998.876000] [<c01032db>] sysenter_past_esp+0x54/0x75 (-4020)
[ 998.876000] ---------------------------
[ 998.876000] | preempt count: 00000002 ]
[ 998.876000] | 2-level deep critical section nesting:
[ 998.876000] ----------------------------------------
[ 998.876000] .. [<c013cf4c>] .... add_preempt_count+0x1c/0x20
[ 998.876000] .....[<c0349f7b>] .. ( <= __schedule+0x4b/0x710)
[ 998.876000] .. [<c013cf4c>] .... add_preempt_count+0x1c/0x20
[ 998.876000] .....[<c034a021>] .. ( <= __schedule+0xf1/0x710)
[ 998.876000]
[ 998.876000] ------------------------------
[ 998.876000] | showing all locks held by: | (aconnect/2708 [f5867010, 116]):
[ 998.876000] ------------------------------
[ 998.876000]
[ 998.876000] #001: [f0ee1264] {(struct rw_semaphore *)(&grp->list_mutex)}
[ 998.876000] ... acquired at: snd_seq_port_disconnect+0x27/0x180 [snd_seq]
[ 998.876000]
[ 998.876000] #002: [f0ee16f8] {(struct rw_semaphore *)(&grp->list_mutex)}
[ 998.876000] ... acquired at: snd_seq_port_disconnect+0x3a/0x180 [snd_seq]
[ 998.876000]
[ 998.876000]
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