From patchwork Tue Jul 17 07:05:23 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: john stultz X-Patchwork-Id: 10034 Return-Path: X-Original-To: patchwork@peony.canonical.com Delivered-To: patchwork@peony.canonical.com Received: from fiordland.canonical.com (fiordland.canonical.com [91.189.94.145]) by peony.canonical.com (Postfix) with ESMTP id 37C3C23E1B for ; Tue, 17 Jul 2012 07:06:04 +0000 (UTC) Received: from mail-yw0-f52.google.com (mail-yw0-f52.google.com [209.85.213.52]) by fiordland.canonical.com (Postfix) with ESMTP id 0878AA185FD for ; Tue, 17 Jul 2012 07:06:03 +0000 (UTC) Received: by mail-yw0-f52.google.com with SMTP id p61so64517yhp.11 for ; Tue, 17 Jul 2012 00:06:03 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=x-forwarded-to:x-forwarded-for:delivered-to:received-spf:from:to:cc :subject:date:message-id:x-mailer:in-reply-to:references :x-content-scanned:x-cbid:x-gm-message-state; bh=ii98QuBiDO04KjHE5DLwywGwK5+siMFHeK8r4mq7Z6Y=; b=NDAcCoN/1GmRraH5d4rwXs483DrtZkFTTlLvTxrVveIYOgbXQBAGX/OR/WWmKtGS66 NjJJS/O2sIg828YWZ0PxquPAe1UbhbQi/9C0w24N+yWvlltjBA/b7zg5fIFntiIn62fz iJANEQ6egGXO8rdhFFm50Yn1EO+DK0h1ZJo1fdvX2hbkty8Lb6M0dpQDAFXc95TYQwiC NIK4KBwnp65GOej6qBSHr5WXfdmaFoFb9+WoVOelWT1kFpVCSeV6bU0gf7enUcrqBCAX fiXi66Er+PYj/ZQbgtAPOguYOhtlriAMxksU4k3HhrEtxMRekt9AGGNuqMuzjQyRYsfk xtfw== Received: by 10.50.46.232 with SMTP id y8mr425080igm.57.1342508763305; Tue, 17 Jul 2012 00:06:03 -0700 (PDT) X-Forwarded-To: linaro-patchwork@canonical.com X-Forwarded-For: patch@linaro.org linaro-patchwork@canonical.com Delivered-To: patches@linaro.org Received: by 10.231.241.2 with SMTP id lc2csp15907ibb; Tue, 17 Jul 2012 00:06:02 -0700 (PDT) Received: by 10.60.12.37 with SMTP id v5mr1771002oeb.25.1342508762338; Tue, 17 Jul 2012 00:06:02 -0700 (PDT) Received: from e32.co.us.ibm.com (e32.co.us.ibm.com. [32.97.110.150]) by mx.google.com with ESMTPS id h7si17477646obn.47.2012.07.17.00.06.02 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 17 Jul 2012 00:06:02 -0700 (PDT) Received-SPF: pass (google.com: domain of johnstul@us.ibm.com designates 32.97.110.150 as permitted sender) client-ip=32.97.110.150; Authentication-Results: mx.google.com; spf=pass (google.com: domain of johnstul@us.ibm.com designates 32.97.110.150 as permitted sender) smtp.mail=johnstul@us.ibm.com Received: from /spool/local by e32.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 17 Jul 2012 01:06:00 -0600 Received: from d01dlp03.pok.ibm.com (9.56.224.17) by e32.co.us.ibm.com (192.168.1.132) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Tue, 17 Jul 2012 01:05:43 -0600 Received: from d01relay06.pok.ibm.com (d01relay06.pok.ibm.com [9.56.227.116]) by d01dlp03.pok.ibm.com (Postfix) with ESMTP id 372D4C9005E for ; Tue, 17 Jul 2012 03:05:42 -0400 (EDT) Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay06.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q6H75fcd45482090 for ; Tue, 17 Jul 2012 03:05:41 -0400 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q6H75eSd016329 for ; Tue, 17 Jul 2012 03:05:40 -0400 Received: from kernel.stglabs.ibm.com (kernel.stglabs.ibm.com [9.114.214.19]) by d01av04.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id q6H75aBS015997; Tue, 17 Jul 2012 03:05:37 -0400 From: John Stultz To: stable@vger.kernel.org Cc: John Stultz , Thomas Gleixner , Prarit Bhargava , Linux Kernel Subject: [PATCH 10/11] 3.2.x: hrtimer: Update hrtimer base offsets each hrtimer_interrupt Date: Tue, 17 Jul 2012 03:05:23 -0400 Message-Id: <1342508724-14527-11-git-send-email-johnstul@us.ibm.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1342508724-14527-1-git-send-email-johnstul@us.ibm.com> References: <1342508724-14527-1-git-send-email-johnstul@us.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12071707-2356-0000-0000-0000006AC688 X-Gm-Message-State: ALoCoQlf4GuCku96Mv1LK71sEWWT1cyrAIkJuvRFMyeFC9opbU8fFmNvFIgXu6fkqLeHBdEeCbtL This is a backport of 5baefd6d84163443215f4a99f6a20f054ef11236 The update of the hrtimer base offsets on all cpus cannot be made atomically from the timekeeper.lock held and interrupt disabled region as smp function calls are not allowed there. clock_was_set(), which enforces the update on all cpus, is called either from preemptible process context in case of do_settimeofday() or from the softirq context when the offset modification happened in the timer interrupt itself due to a leap second. In both cases there is a race window for an hrtimer interrupt between dropping timekeeper lock, enabling interrupts and clock_was_set() issuing the updates. Any interrupt which arrives in that window will see the new time but operate on stale offsets. So we need to make sure that an hrtimer interrupt always sees a consistent state of time and offsets. ktime_get_update_offsets() allows us to get the current monotonic time and update the per cpu hrtimer base offsets from hrtimer_interrupt() to capture a consistent state of monotonic time and the offsets. The function replaces the existing ktime_get() calls in hrtimer_interrupt(). The overhead of the new function vs. ktime_get() is minimal as it just adds two store operations. This ensures that any changes to realtime or boottime offsets are noticed and stored into the per-cpu hrtimer base structures, prior to any hrtimer expiration and guarantees that timers are not expired early. Signed-off-by: John Stultz Reviewed-by: Ingo Molnar Acked-by: Peter Zijlstra Acked-by: Prarit Bhargava Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1341960205-56738-8-git-send-email-johnstul@us.ibm.com Signed-off-by: Thomas Gleixner Cc: Prarit Bhargava Cc: Thomas Gleixner Cc: Linux Kernel Signed-off-by: John Stultz --- kernel/hrtimer.c | 28 ++++++++++++++-------------- 1 file changed, 14 insertions(+), 14 deletions(-) diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 8f320af..6db7a5e 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -657,6 +657,14 @@ static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer, return 0; } +static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base) +{ + ktime_t *offs_real = &base->clock_base[HRTIMER_BASE_REALTIME].offset; + ktime_t *offs_boot = &base->clock_base[HRTIMER_BASE_BOOTTIME].offset; + + return ktime_get_update_offsets(offs_real, offs_boot); +} + /* * Retrigger next event is called after clock was set * @@ -665,22 +673,12 @@ static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer, static void retrigger_next_event(void *arg) { struct hrtimer_cpu_base *base = &__get_cpu_var(hrtimer_bases); - struct timespec realtime_offset, xtim, wtm, sleep; if (!hrtimer_hres_active()) return; - /* Optimized out for !HIGH_RES */ - get_xtime_and_monotonic_and_sleep_offset(&xtim, &wtm, &sleep); - set_normalized_timespec(&realtime_offset, -wtm.tv_sec, -wtm.tv_nsec); - - /* Adjust CLOCK_REALTIME offset */ raw_spin_lock(&base->lock); - base->clock_base[HRTIMER_BASE_REALTIME].offset = - timespec_to_ktime(realtime_offset); - base->clock_base[HRTIMER_BASE_BOOTTIME].offset = - timespec_to_ktime(sleep); - + hrtimer_update_base(base); hrtimer_force_reprogram(base, 0); raw_spin_unlock(&base->lock); } @@ -710,7 +708,6 @@ static int hrtimer_switch_to_hres(void) base->clock_base[i].resolution = KTIME_HIGH_RES; tick_setup_sched_timer(); - /* "Retrigger" the interrupt to get things going */ retrigger_next_event(NULL); local_irq_restore(flags); @@ -1264,7 +1261,7 @@ void hrtimer_interrupt(struct clock_event_device *dev) dev->next_event.tv64 = KTIME_MAX; raw_spin_lock(&cpu_base->lock); - entry_time = now = ktime_get(); + entry_time = now = hrtimer_update_base(cpu_base); retry: expires_next.tv64 = KTIME_MAX; /* @@ -1342,9 +1339,12 @@ retry: * We need to prevent that we loop forever in the hrtimer * interrupt routine. We give it 3 attempts to avoid * overreacting on some spurious event. + * + * Acquire base lock for updating the offsets and retrieving + * the current time. */ raw_spin_lock(&cpu_base->lock); - now = ktime_get(); + now = hrtimer_update_base(cpu_base); cpu_base->nr_retries++; if (++retries < 3) goto retry;