From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965508AbcIPUPN (ORCPT ); Fri, 16 Sep 2016 16:15:13 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:35762 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965321AbcIPUOo (ORCPT ); Fri, 16 Sep 2016 16:14:44 -0400 From: Nicolai Stange To: Thomas Gleixner Cc: John Stultz , linux-kernel@vger.kernel.org, Nicolai Stange Subject: [RFC v7 17/23] clockevents: use ->min_delta_ticks_adjusted to program minimum delta Date: Fri, 16 Sep 2016 22:11:58 +0200 Message-Id: <20160916201204.9424-6-nicstange@gmail.com> X-Mailer: git-send-email 2.10.0 In-Reply-To: <20160916200851.9273-1-nicstange@gmail.com> References: <20160916200851.9273-1-nicstange@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The use of a clockevent device's ->min_delta_ns in the event programming path hinders upcoming changes to the clockevent core making it NTP correction aware: both, ->mult and ->min_delta_ns would need to get updated as well as consumed atomically and we'd rather like to avoid any locking here. We already have got ->min_delta_ticks_adjusted which - resembles the value of ->min_delta_ns - and is guaranteed to be always >= the hardware's hard limit ->min_delta_ticks and thus, can be used w/o locking as we don't care for small deviations. In both implementations of clockevents_program_min_delta(), don't calculate the event's deadline from ->min_delta_ns, but use its drop-in replacement ->min_delta_ticks_adjusted. Signed-off-by: Nicolai Stange --- kernel/time/clockevents.c | 15 ++------------- 1 file changed, 2 insertions(+), 13 deletions(-) diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c index 8983fee..aa7b325 100644 --- a/kernel/time/clockevents.c +++ b/kernel/time/clockevents.c @@ -246,19 +246,14 @@ static int clockevents_increase_min_delta(struct clock_event_device *dev) */ static int clockevents_program_min_delta(struct clock_event_device *dev) { - unsigned long long clc; - int64_t delta; int i; for (i = 0;;) { - delta = dev->min_delta_ns; - if (clockevent_state_shutdown(dev)) return 0; dev->retries++; - clc = ((unsigned long long) delta * dev->mult) >> dev->shift; - if (dev->set_next_event((unsigned long) clc, dev) == 0) + if (!dev->set_next_event(dev->min_delta_ticks_adjusted, dev)) return 0; if (++i > 2) { @@ -284,17 +279,11 @@ static int clockevents_program_min_delta(struct clock_event_device *dev) */ static int clockevents_program_min_delta(struct clock_event_device *dev) { - unsigned long long clc; - int64_t delta; - - delta = dev->min_delta_ns; - if (clockevent_state_shutdown(dev)) return 0; dev->retries++; - clc = ((unsigned long long) delta * dev->mult) >> dev->shift; - return dev->set_next_event((unsigned long) clc, dev); + return dev->set_next_event(dev->min_delta_ticks_adjusted, dev); } #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */ -- 2.10.0