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| author |   Takashi Iwai <tiwai@suse.de> | 2021-09-29 10:08:37 +0200 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2021-09-30 13:55:19 +0200 |
| commit | 86a42ad07905110f82648853c0ea3434b4eab173 (patch) | |
| tree | 4803a5fb707e50d2a269ae9efc74703fa9e95e94 /sound/usb/card.h | |
| parent | ALSA: usb-audio: Restrict rates for the shared clocks (diff) | |
| download | linux-dev-86a42ad07905110f82648853c0ea3434b4eab173.tar.xz linux-dev-86a42ad07905110f82648853c0ea3434b4eab173.zip | |
ALSA: usb-audio: Fix possible race at sync of urb completions
USB-audio driver tries to sync with the clear of all pending URBs in
wait_clear_urbs(), and it waits for all bits in active_mask getting
cleared. This works fine for the normal operations, but when a stream
is managed in the implicit feedback mode, there is still a very thin
race window: namely, in snd_complete_usb(), the active_mask bit for
the current URB is once cleared before re-submitted in
queue_pending_output_urbs(). If wait_clear_urbs() is called during
that period, it may pass the test and go forward even though there may
be a still pending URB.
For covering it, this patch adds a new counter to each endpoint to
keep the number of in-flight URBs, and changes wait_clear_urbs()
checking this number instead. The counter is decremented at the end
of URB complete, hence the reference is kept as long as the URB
complete is in process.
Link: https://lore.kernel.org/r/20210929080844.11583-3-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/usb/card.h')
| -rw-r--r-- | sound/usb/card.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/sound/usb/card.h b/sound/usb/card.h index 3329ce710cb9..746a765b2437 100644 --- a/sound/usb/card.h +++ b/sound/usb/card.h @@ -97,6 +97,7 @@ struct snd_usb_endpoint { unsigned int nominal_queue_size; /* total buffer sizes in URBs */ unsigned long active_mask; /* bitmask of active urbs */ unsigned long unlink_mask; /* bitmask of unlinked urbs */ + atomic_t submitted_urbs; /* currently submitted urbs */ char *syncbuf; /* sync buffer for all sync URBs */ dma_addr_t sync_dma; /* DMA address of syncbuf */ |