From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-Id: <20120518212649.411772717@linuxfoundation.org> Date: Fri, 18 May 2012 14:26:51 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, David Henningsson , Arun Raghavan , Takashi Iwai Subject: [ 02/47] ALSA: HDA: Lessen CPU usage when waiting for chip to respond In-Reply-To: <20120518212701.GA5023@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Henningsson commit 32cf4023e689ad5b3a81a749d8cc99d7f184cb99 upstream. 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 Tested-by: Arun Raghavan Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/pci/hda/hda_intel.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/sound/pci/hda/hda_intel.c +++ b/sound/pci/hda/hda_intel.c @@ -779,11 +779,13 @@ static unsigned int azx_rirb_get_respons { 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); @@ -799,7 +801,7 @@ static unsigned int azx_rirb_get_respons } 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);