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ALSA: HDA: Lessen CPU usage when waiting for chip to respond

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When an IRQ for some reason gets lost, we wait up to a second using
udelay, which is CPU intensive. This patch improves the situation by
waiting about 30 ms in the CPU intensive mode, then stepping down to
using msleep(2) instead. In essence, we trade some granularity in
exchange for less CPU consumption when the waiting time is a bit longer.

As a result, PulseAudio should no longer be killed by the kernel
for taking up to much RT-prio CPU time. At least not for *this* reason.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Tested-by: Arun Raghavan <arun.raghavan@collabora.co.uk>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
David Henningsson 2012-05-04 11:05:55 +02:00 committed by Takashi Iwai
parent 619a341b78
commit 32cf4023e6
1 changed files with 4 additions and 2 deletions
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6
sound/pci/hda/hda_intel.c
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@ -783,11 +783,13 @@ static unsigned int azx_rirb_get_response(struct hda_bus *bus,
{
struct azx *chip = bus->private_data;
unsigned long timeout;
unsigned long loopcounter;
int do_poll = 0;
again:
timeout = jiffies + msecs_to_jiffies(1000);
for (;;) {
for (loopcounter = 0;; loopcounter++) {
if (chip->polling_mode || do_poll) {
spin_lock_irq(&chip->reg_lock);
azx_update_rirb(chip);
@ -803,7 +805,7 @@ static unsigned int azx_rirb_get_response(struct hda_bus *bus,
}
if (time_after(jiffies, timeout))
break;
if (bus->needs_damn_long_delay)
if (bus->needs_damn_long_delay || loopcounter > 3000)
msleep(2); /* temporary workaround */
else {
udelay(10);