From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031177Ab2ERDJh (ORCPT ); Thu, 17 May 2012 23:09:37 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:40396 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762545Ab2ERCw1 (ORCPT ); Thu, 17 May 2012 22:52:27 -0400 Message-Id: <20120518023255.053534199@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Fri, 18 May 2012 03:32:59 +0100 From: Ben Hutchings 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: [ 05/53] ALSA: HDA: Lessen CPU usage when waiting for chip to respond In-Reply-To: <20120518023254.339945758@decadent.org.uk> X-SA-Exim-Connect-IP: 192.168.4.185 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.18-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: Ben Hutchings --- sound/pci/hda/hda_intel.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c index 6e958bf..1f35052 100644 --- a/sound/pci/hda/hda_intel.c +++ b/sound/pci/hda/hda_intel.c @@ -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); -- 1.7.10