[alsa-devel] [PATCH] RME HDSPM MADI lock fix

Jörn Nettingsmeier nettings at stackingdwarves.net
Sun Jun 5 11:57:57 CEST 2011

hi *!

while we were trying to debug the midi-related xruns in the current 
driver, i came across what looks like an unrelated locking bug to me:

static int snd_hdspm_midi_input_read (struct hdspm_midi *hmidi)
         spin_lock_irqsave (&hmidi->lock, flags); <---------------
         n_pending = snd_hdspm_midi_input_available (hmidi->hdspm, 
         if (n_pending > 0) {
                 if (hmidi->input) {
                         if (n_pending > (int)sizeof (buf))
                                 n_pending = sizeof (buf);
                         for (i = 0; i < n_pending; ++i)
                                 buf[i] = snd_hdspm_midi_read_byte 
                         if (n_pending)
                                 snd_rawmidi_receive (hmidi->input, buf,
                 } else {
                         /* flush the MIDI input FIFO */
                         while (n_pending--)
                                 snd_hdspm_midi_read_byte (hmidi->hdspm,
         hmidi->pending = 0;

         hmidi->hdspm->control_register |= hmidi->ie;<------- !!!
         hdspm_write(hmidi->hdspm, HDSPM_controlRegister,

         spin_unlock_irqrestore (&hmidi->lock, flags);<---------
         return snd_hdspm_midi_output_write (hmidi);

if i understand this whole business correctly, we should be holding the 
hdspm lock here, not the hmidi one.

please review the attached patch and apply if you think it's ok.



Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487

Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister (VDT)

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