Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753556AbcKSQLd (ORCPT ); Sat, 19 Nov 2016 11:11:33 -0500 Received: from mail-wm0-f67.google.com ([74.125.82.67]:36322 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753446AbcKSQLc (ORCPT ); Sat, 19 Nov 2016 11:11:32 -0500 From: Nicolai Stange To: Thomas Gleixner Cc: John Stultz , linux-kernel@vger.kernel.org, Nicolai Stange Subject: [RFC v8 15/28] clockevents: use ->min_delta_ticks_adjusted to program minimum delta Date: Sat, 19 Nov 2016 17:10:23 +0100 Message-Id: <20161119161036.12679-4-nicstange@gmail.com> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20161119160055.12491-1-nicstange@gmail.com> References: <20161119160055.12491-1-nicstange@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2199 Lines: 67 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 8d32c2c..74b05dd 100644 --- a/kernel/time/clockevents.c +++ b/kernel/time/clockevents.c @@ -243,19 +243,14 @@ 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) { @@ -281,17 +276,11 @@ 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 */ -- 2.10.2