From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752658AbaBWACT (ORCPT ); Sat, 22 Feb 2014 19:02:19 -0500 Received: from www.linutronix.de ([62.245.132.108]:49263 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752039AbaBWACS (ORCPT ); Sat, 22 Feb 2014 19:02:18 -0500 Date: Sun, 23 Feb 2014 01:02:25 +0100 (CET) From: Thomas Gleixner To: Linus Torvalds cc: Andrew Morton , LKML , Ingo Molnar , "H. Peter Anvin" Subject: [GIT Pull] timer fixes for 3.14 Message-ID: User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Linus, please pull the latest timers-urgent-for-linus git tree from: git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers-urgent-for-linus Short summary: * Serialize the registration of a new sched_clock in the currently ARM only generic sched_clock facilty to avoid sched_clock havoc Thanks, tglx ------------------> Stephen Boyd (1): sched_clock: Prevent callers from seeing half-updated data kernel/time/sched_clock.c | 46 ++++++++++++++++++++++++++++----------------- 1 file changed, 29 insertions(+), 17 deletions(-) diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c index 0abb364..4d23dc4 100644 --- a/kernel/time/sched_clock.c +++ b/kernel/time/sched_clock.c @@ -116,20 +116,42 @@ static enum hrtimer_restart sched_clock_poll(struct hrtimer *hrt) void __init sched_clock_register(u64 (*read)(void), int bits, unsigned long rate) { + u64 res, wrap, new_mask, new_epoch, cyc, ns; + u32 new_mult, new_shift; + ktime_t new_wrap_kt; unsigned long r; - u64 res, wrap; char r_unit; if (cd.rate > rate) return; WARN_ON(!irqs_disabled()); - read_sched_clock = read; - sched_clock_mask = CLOCKSOURCE_MASK(bits); - cd.rate = rate; /* calculate the mult/shift to convert counter ticks to ns. */ - clocks_calc_mult_shift(&cd.mult, &cd.shift, rate, NSEC_PER_SEC, 3600); + clocks_calc_mult_shift(&new_mult, &new_shift, rate, NSEC_PER_SEC, 3600); + + new_mask = CLOCKSOURCE_MASK(bits); + + /* calculate how many ns until we wrap */ + wrap = clocks_calc_max_nsecs(new_mult, new_shift, 0, new_mask); + new_wrap_kt = ns_to_ktime(wrap - (wrap >> 3)); + + /* update epoch for new counter and update epoch_ns from old counter*/ + new_epoch = read(); + cyc = read_sched_clock(); + ns = cd.epoch_ns + cyc_to_ns((cyc - cd.epoch_cyc) & sched_clock_mask, + cd.mult, cd.shift); + + raw_write_seqcount_begin(&cd.seq); + read_sched_clock = read; + sched_clock_mask = new_mask; + cd.rate = rate; + cd.wrap_kt = new_wrap_kt; + cd.mult = new_mult; + cd.shift = new_shift; + cd.epoch_cyc = new_epoch; + cd.epoch_ns = ns; + raw_write_seqcount_end(&cd.seq); r = rate; if (r >= 4000000) { @@ -141,22 +163,12 @@ void __init sched_clock_register(u64 (*read)(void), int bits, } else r_unit = ' '; - /* calculate how many ns until we wrap */ - wrap = clocks_calc_max_nsecs(cd.mult, cd.shift, 0, sched_clock_mask); - cd.wrap_kt = ns_to_ktime(wrap - (wrap >> 3)); - /* calculate the ns resolution of this counter */ - res = cyc_to_ns(1ULL, cd.mult, cd.shift); + res = cyc_to_ns(1ULL, new_mult, new_shift); + pr_info("sched_clock: %u bits at %lu%cHz, resolution %lluns, wraps every %lluns\n", bits, r, r_unit, res, wrap); - update_sched_clock(); - - /* - * Ensure that sched_clock() starts off at 0ns - */ - cd.epoch_ns = 0; - /* Enable IRQ time accounting if we have a fast enough sched_clock */ if (irqtime > 0 || (irqtime == -1 && rate >= 1000000)) enable_sched_clock_irqtime();