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Message-ID: <20240728123041.330216-3-edmund.raile@protonmail.com>
Date: Sun, 28 Jul 2024 12:31:03 +0000
From: Edmund Raile <edmund.raile@...tonmail.com>
To: o-takashi@...amocchi.jp, clemens@...isch.de
Cc: tiwai@...e.com, alsa-devel@...a-project.org, linux-sound@...r.kernel.org, linux-kernel@...r.kernel.org, edmund.raile@...tonmail.com, stable@...r.kernel.org
Subject: [PATCH v2 2/2] ALSA: firewire-lib: restore process context workqueue to prevent deadlock
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 a deadlock with eventual system freeze under ALSA operation:
A. In the process context
* (lock A) Acquiring spin_lock by snd_pcm_stream_lock_irq() in
snd_pcm_status64()
* (lock B) Then attempt to enter tasklet
B. In the softIRQ context
* (lock B) Enter tasklet
* (lock A) Attempt to acquire spin_lock by
snd_pcm_stream_lock_irqsave() in snd_pcm_period_elapsed()
? 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
between ALSA substream process context spin_lock of
snd_pcm_stream_lock_irq() in snd_pcm_status64()
and OHCI 1394 IT softIRQ context spin_lock of
snd_pcm_stream_lock_irqsave() in snd_pcm_period_elapsed().
Cc: stable@...r.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@...ton.me>
Signed-off-by: Edmund Raile <edmund.raile@...tonmail.com>
---
sound/firewire/amdtp-stream.c | 21 ++++++++-------------
1 file changed, 8 insertions(+), 13 deletions(-)
diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c
index 31201d506a21..c037d7de1fdc 100644
--- a/sound/firewire/amdtp-stream.c
+++ b/sound/firewire/amdtp-stream.c
@@ -615,16 +615,9 @@ 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)
+ // wq used with amdtp_domain_stream_pcm_pointer() to prevent deadlock
+ queue_work(system_highpri_wq, &s->period_work);
}
}
@@ -1866,9 +1859,11 @@ unsigned long amdtp_domain_stream_pcm_pointer(struct amdtp_domain *d,
// 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())
+ // use wq to prevent deadlock between process context spin_lock
+ // of snd_pcm_stream_lock_irq() in snd_pcm_status64() and
+ // softIRQ context spin_lock of snd_pcm_stream_lock_irqsave()
+ // in snd_pcm_period_elapsed()
+ if ((!in_softirq()) && (current_work() != &s->period_work))
fw_iso_context_flush_completions(irq_target->context);
}
--
2.45.2
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