[alsa-devel] [PATCH v2] ALSA: firewire-lib: Fix stall of process context at packet error
Takashi Sakamoto
o-takashi at sakamocchi.jp
Fri Jun 9 15:20:31 CEST 2017
At Linux v3.5, packet processing can be done in process context of ALSA
PCM application as well as software IRQ context for OHCI 1394. Below is
an example of the callgraph (some calls are omitted).
ioctl(2) with e.g. HWSYNC
(sound/core/pcm_native.c)
->snd_pcm_common_ioctl1()
->snd_pcm_hwsync()
->snd_pcm_stream_lock_irq
(sound/core/pcm_lib.c)
->snd_pcm_update_hw_ptr()
->snd_pcm_update_hw_ptr0()
->struct snd_pcm_ops.pointer()
(sound/firewire/*)
= Each handler on drivers in ALSA firewire stack
(sound/firewire/amdtp-stream.c)
->amdtp_stream_pcm_pointer()
(drivers/firewire/core-iso.c)
->fw_iso_context_flush_completions()
->struct fw_card_driver.flush_iso_completion()
(drivers/firewire/ohci.c)
= flush_iso_completions()
->struct fw_iso_context.callback.sc
(sound/firewire/amdtp-stream.c)
= in_stream_callback() or out_stream_callback()
->...
->snd_pcm_stream_unlock_irq
When packet queueing error occurs or detecting invalid packets in
'in_stream_callback()' or 'out_stream_callback()', 'snd_pcm_stop_xrun()'
is called on local CPU with disabled IRQ.
(sound/firewire/amdtp-stream.c)
in_stream_callback() or out_stream_callback()
->amdtp_stream_pcm_abort()
->snd_pcm_stop_xrun()
->snd_pcm_stream_lock_irqsave()
->snd_pcm_stop()
->snd_pcm_stream_unlock_irqrestore()
The process is stalled on the CPU due to attempt to acquire recursive lock.
[ 562.630853] INFO: rcu_sched detected stalls on CPUs/tasks:
[ 562.630861] 2-...: (1 GPs behind) idle=37d/140000000000000/0 softirq=38323/38323 fqs=7140
[ 562.630862] (detected by 3, t=15002 jiffies, g=21036, c=21035, q=5933)
[ 562.630866] Task dump for CPU 2:
[ 562.630867] alsa-source-OXF R running task 0 6619 1 0x00000008
[ 562.630870] Call Trace:
[ 562.630876] ? vt_console_print+0x79/0x3e0
[ 562.630880] ? msg_print_text+0x9d/0x100
[ 562.630883] ? up+0x32/0x50
[ 562.630885] ? irq_work_queue+0x8d/0xa0
[ 562.630886] ? console_unlock+0x2b6/0x4b0
[ 562.630888] ? vprintk_emit+0x312/0x4a0
[ 562.630892] ? dev_vprintk_emit+0xbf/0x230
[ 562.630895] ? do_sys_poll+0x37a/0x550
[ 562.630897] ? dev_printk_emit+0x4e/0x70
[ 562.630900] ? __dev_printk+0x3c/0x80
[ 562.630903] ? _raw_spin_lock+0x20/0x30
[ 562.630909] ? snd_pcm_stream_lock+0x31/0x50 [snd_pcm]
[ 562.630914] ? _snd_pcm_stream_lock_irqsave+0x2e/0x40 [snd_pcm]
[ 562.630918] ? snd_pcm_stop_xrun+0x16/0x70 [snd_pcm]
[ 562.630922] ? in_stream_callback+0x3e6/0x450 [snd_firewire_lib]
[ 562.630925] ? handle_ir_packet_per_buffer+0x8e/0x1a0 [firewire_ohci]
[ 562.630928] ? ohci_flush_iso_completions+0xa3/0x130 [firewire_ohci]
[ 562.630932] ? fw_iso_context_flush_completions+0x15/0x20 [firewire_core]
[ 562.630935] ? amdtp_stream_pcm_pointer+0x2d/0x40 [snd_firewire_lib]
[ 562.630938] ? pcm_capture_pointer+0x19/0x20 [snd_oxfw]
[ 562.630943] ? snd_pcm_update_hw_ptr0+0x47/0x3d0 [snd_pcm]
[ 562.630945] ? poll_select_copy_remaining+0x150/0x150
[ 562.630947] ? poll_select_copy_remaining+0x150/0x150
[ 562.630952] ? snd_pcm_update_hw_ptr+0x10/0x20 [snd_pcm]
[ 562.630956] ? snd_pcm_hwsync+0x45/0xb0 [snd_pcm]
[ 562.630960] ? snd_pcm_common_ioctl1+0x1ff/0xc90 [snd_pcm]
[ 562.630962] ? futex_wake+0x90/0x170
[ 562.630966] ? snd_pcm_capture_ioctl1+0x136/0x260 [snd_pcm]
[ 562.630970] ? snd_pcm_capture_ioctl+0x27/0x40 [snd_pcm]
[ 562.630972] ? do_vfs_ioctl+0xa3/0x610
[ 562.630974] ? vfs_read+0x11b/0x130
[ 562.630976] ? SyS_ioctl+0x79/0x90
[ 562.630978] ? entry_SYSCALL_64_fastpath+0x1e/0xad
This commit fixes the above bug by removing the calls of
'amdtp_stream_pcm_abort()' from packet handler. Instead, in
'struct snd_pcm_ops.pointer', SNDRV_PCM_POS_XRUN is returned to take ALSA
PCM core to stop PCM substream safely.
Suggested-by: Clemens Ladisch <clemens at ladisch.de>
Fixes: e9148dddc3c7("ALSA: firewire-lib: flush completed packets when reading PCM position")
Cc: <stable at vger.kernel.org> # 4.9+
Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
---
sound/firewire/amdtp-stream.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c
index 9678bc75dc5b..de4f6b6dbd47 100644
--- a/sound/firewire/amdtp-stream.c
+++ b/sound/firewire/amdtp-stream.c
@@ -701,7 +701,7 @@ static void out_stream_callback(struct fw_iso_context *context, u32 tstamp,
cycle = increment_cycle_count(cycle, 1);
if (s->handle_packet(s, 0, cycle, i) < 0) {
s->packet_index = -1;
- amdtp_stream_pcm_abort(s);
+ WRITE_ONCE(s->pcm_buffer_pointer, SNDRV_PCM_POS_XRUN);
return;
}
}
@@ -753,7 +753,7 @@ static void in_stream_callback(struct fw_iso_context *context, u32 tstamp,
/* Queueing error or detecting invalid payload. */
if (i < packets) {
s->packet_index = -1;
- amdtp_stream_pcm_abort(s);
+ WRITE_ONCE(s->pcm_buffer_pointer, SNDRV_PCM_POS_XRUN);
return;
}
--
2.11.0
More information about the Alsa-devel
mailing list