@@ -615,16 +615,8 @@ static void update_pcm_pointers(struct amdtp_stream *s,
// The program in user process should periodically check the status of intermediate
// buffer associated to PCM substream to process PCM frames in the buffer, instead
// of receiving notification of period elapsed by poll wait.
- if (!pcm->runtime->no_period_wakeup) {
- if (in_softirq()) {
- // In software IRQ context for 1394 OHCI.
- snd_pcm_period_elapsed(pcm);
- } else {
- // In process context of ALSA PCM application under acquired lock of
- // PCM substream.
- snd_pcm_period_elapsed_under_stream_lock(pcm);
- }
- }
+ if (!pcm->runtime->no_period_wakeup)
+ queue_work(system_highpri_wq, &s->period_work);
}
}
@@ -1864,11 +1856,22 @@ unsigned long amdtp_domain_stream_pcm_pointer(struct amdtp_domain *d,
{
struct amdtp_stream *irq_target = d->irq_target;
- // Process isochronous packets queued till recent isochronous cycle to handle PCM frames.
if (irq_target && amdtp_stream_running(irq_target)) {
- // In software IRQ context, the call causes dead-lock to disable the tasklet
- // synchronously.
- if (!in_softirq())
+ // This function is called in software IRQ context of
+ // period_work or process context.
+ //
+ // When the software IRQ context was scheduled by software IRQ
+ // context of IT contexts, queued packets were already handled.
+ // Therefore, no need to flush the queue in buffer furthermore.
+ //
+ // When the process context reach here, some packets will be
+ // already queued in the buffer. These packets should be handled
+ // immediately to keep better granularity of PCM pointer.
+ //
+ // Later, the process context will sometimes schedules software
+ // IRQ context of the period_work. Then, no need to flush the
+ // queue by the same reason as described in the above
+ if (current_work() != &s->period_work)
fw_iso_context_flush_completions(irq_target->context);
}
Commit 7ba5ca32fe6e ("ALSA: firewire-lib: operate for period elapse event in process context") removed the process context workqueue from amdtp_domain_stream_pcm_pointer() and update_pcm_pointers() to remove its overhead. With RME Fireface 800, this lead to a regression since Kernels 5.14.0, causing an AB/BA deadlock competition for the substream lock with eventual system freeze under ALSA operation: thread 0: * (lock A) acquire substream lock by snd_pcm_stream_lock_irq() in snd_pcm_status64() * (lock B) wait for tasklet to finish by calling tasklet_unlock_spin_wait() in tasklet_disable_in_atomic() in ohci_flush_iso_completions() of ohci.c thread 1: * (lock B) enter tasklet * (lock A) attempt to acquire substream lock, waiting for it to be released: snd_pcm_stream_lock_irqsave() in snd_pcm_period_elapsed() in update_pcm_pointers() in process_ctx_payloads() in process_rx_packets() of amdtp-stream.c ? tasklet_unlock_spin_wait </NMI> <TASK> ohci_flush_iso_completions firewire_ohci amdtp_domain_stream_pcm_pointer snd_firewire_lib snd_pcm_update_hw_ptr0 snd_pcm snd_pcm_status64 snd_pcm ? native_queued_spin_lock_slowpath </NMI> <IRQ> _raw_spin_lock_irqsave snd_pcm_period_elapsed snd_pcm process_rx_packets snd_firewire_lib irq_target_callback snd_firewire_lib handle_it_packet firewire_ohci context_tasklet firewire_ohci Restore the process context work queue to prevent deadlock AB/BA deadlock competition for ALSA substream lock of snd_pcm_stream_lock_irq() in snd_pcm_status64() and snd_pcm_stream_lock_irqsave() in snd_pcm_period_elapsed(). commit 7ba5ca32fe6e ("ALSA: firewire-lib: operate for period elapse event in process context") Cc: stable@vger.kernel.org Fixes: 7ba5ca32fe6e ("ALSA: firewire-lib: operate for period elapse event in process context") Link: https://lore.kernel.org/r/kwryofzdmjvzkuw6j3clftsxmoolynljztxqwg76hzeo4simnl@jn3eo7pe642q/ Reported-by: edmund.raile <edmund.raile@proton.me> Closes: https://lore.kernel.org/r/kwryofzdmjvzkuw6j3clftsxmoolynljztxqwg76hzeo4simnl@jn3eo7pe642q/ Signed-off-by: Edmund Raile <edmund.raile@protonmail.com> --- sound/firewire/amdtp-stream.c | 31 +++++++++++++++++-------------- 1 file changed, 17 insertions(+), 14 deletions(-)