| Message ID | 20240728122614.329544-1-edmund.raile@protonmail.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | ALSA: firewire-lib: restore process context workqueue to prevent deadlock | expand |
Hi, On Sun, Jul 28, 2024 at 12:26:21PM +0000, Edmund Raile wrote: > This patchset serves to prevent a deadlock between > process context and softIRQ context: (snip) > Edmund Raile (2): > ALSA: firewire-lib: restore workqueue for process context > ALSA: firewire-lib: prevent deadlock between process and softIRQ > context > > sound/firewire/amdtp-stream.c | 36 ++++++++++++++++++++++------------- > sound/firewire/amdtp-stream.h | 1 + > 2 files changed, 24 insertions(+), 13 deletions(-) Thank you for your sending the revised patches, it looks better than the previous one. However, I have an additional request. In this case, it is enough to execute 'revert' subcommand[1] of git(1), like: $ git revert -s b5b519965c4c $ git revert -s 7ba5ca32fe6e It is permitted to add postscript to the commit comment generated by the above command. You see my recent post as an example[2]. Just for safe, it is preferable to execute 'scripts/checkpatch.pl' in kernel tree to check the patchset generated by send-email subcommand[3]. [1] https://git-scm.com/docs/git-revert [2] https://lore.kernel.org/lkml/20240725161648.130404-1-o-takashi@sakamocchi.jp/ [3] https://git-scm.com/docs/git-send-email Thanks Takashi Sakamoto
This patchset serves to prevent a deadlock between process context and softIRQ context: 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 The issue has been reported as a regression of kernel 5.14: Link: https://lore.kernel.org/regressions/kwryofzdmjvzkuw6j3clftsxmoolynljztxqwg76hzeo4simnl@jn3eo7pe642q/T/#u ("[REGRESSION] ALSA: firewire-lib: snd_pcm_period_elapsed deadlock with Fireface 800") 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. Commit b5b519965c4c ("ALSA: firewire-lib: obsolete workqueue for period update") belongs to the same patch series and removed the now-unused workqueue entirely. Though being observed on RME Fireface 800, this issue would affect all Firewire audio interfaces using ohci amdtp + pcm streaming. ALSA streaming, especially under intensive CPU load will reveal this issue the soonest due to issuing more hardIRQs, with time to occurrence ranging from 2 secons to 30 minutes after starting playback. to reproduce the issue: direct ALSA playback to the device: mpv --audio-device=alsa/sysdefault:CARD=Fireface800 Spor-Ignition.flac Time to occurrence: 2s to 30m Likelihood increased by: - high CPU load stress --cpu $(nproc) - switching between applications via workspaces tested with i915 in Xfce PulsaAudio / PipeWire conceal the issue as they run PCM substream without period wakeup mode, issuing less hardIRQs. Backport note: Also applies to and fixes on (tested): 6.10.2, 6.9.12, 6.6.43, 6.1.102, 5.15.164 Edmund Raile (2): ALSA: firewire-lib: restore workqueue for process context ALSA: firewire-lib: prevent deadlock between process and softIRQ context sound/firewire/amdtp-stream.c | 36 ++++++++++++++++++++++------------- sound/firewire/amdtp-stream.h | 1 + 2 files changed, 24 insertions(+), 13 deletions(-)