From patchwork Tue Jul 17 17:33:57 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: john stultz X-Patchwork-Id: 10056 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 456F524027 for ; Tue, 17 Jul 2012 17:35:20 +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 15A48A182AE for ; Tue, 17 Jul 2012 17:35:19 +0000 (UTC) Received: by mail-yw0-f52.google.com with SMTP id p61so713266yhp.11 for ; Tue, 17 Jul 2012 10:35:19 -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=NEp/gU7LYywlxEQDlV+RB/l+Z1l8ELfprXDwJbb+Gj8=; b=Y3LwgvazCK9nMnCzToRwf7h5aP1VpDXLx5sfKfR94yCanCebXNPisknfkUI83TWf+A K8ZCikDYtMcVC2rpfwUZD0fMshMtnTpYqQlDTY4FXYjrelR/0fq/M1YFgjEpLccUzwXa EYPzBzAbL5zf80b2tM5HB0erlQoMRyI7OQ87QClGfy6Ba735kB2Bi8kD0XCmfNN6IUlf Z1Y1UtjhP0IjYFSrVpyvCYKeg9+JYFs7Pj+DrxTpaNegezmTlLVUQoyocnHdZsMQHWVg W06scQ6x8CUQE9roGlHh8KH40UjfQAoKhSk7b47SPVkdMuFkelfZ1QjEYpFhBhNNurSU gH5A== Received: by 10.50.57.167 with SMTP id j7mr2110807igq.53.1342546519505; Tue, 17 Jul 2012 10:35:19 -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 lc2csp22534ibb; Tue, 17 Jul 2012 10:35:18 -0700 (PDT) Received: by 10.182.136.74 with SMTP id py10mr4631349obb.27.1342546518095; Tue, 17 Jul 2012 10:35:18 -0700 (PDT) Received: from e39.co.us.ibm.com (e39.co.us.ibm.com. [32.97.110.160]) by mx.google.com with ESMTPS id s6si18980245obw.179.2012.07.17.10.35.17 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 17 Jul 2012 10:35:18 -0700 (PDT) Received-SPF: pass (google.com: domain of johnstul@us.ibm.com designates 32.97.110.160 as permitted sender) client-ip=32.97.110.160; Authentication-Results: mx.google.com; spf=pass (google.com: domain of johnstul@us.ibm.com designates 32.97.110.160 as permitted sender) smtp.mail=johnstul@us.ibm.com Received: from /spool/local by e39.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 17 Jul 2012 11:35:17 -0600 Received: from d03dlp03.boulder.ibm.com (9.17.202.179) by e39.co.us.ibm.com (192.168.1.139) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Tue, 17 Jul 2012 11:35:16 -0600 Received: from d03relay02.boulder.ibm.com (d03relay02.boulder.ibm.com [9.17.195.227]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id 7DBE519D804C for ; Tue, 17 Jul 2012 17:35:13 +0000 (WET) Received: from d03av06.boulder.ibm.com (d03av06.boulder.ibm.com [9.17.195.245]) by d03relay02.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q6HHYlKq163898 for ; Tue, 17 Jul 2012 11:34:55 -0600 Received: from d03av06.boulder.ibm.com (loopback [127.0.0.1]) by d03av06.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q6HHZOnp016836 for ; Tue, 17 Jul 2012 11:35:24 -0600 Received: from kernel.stglabs.ibm.com (kernel.stglabs.ibm.com [9.114.214.19]) by d03av06.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id q6HHZEEB015928; Tue, 17 Jul 2012 11:35:24 -0600 From: John Stultz To: stable@vger.kernel.org Cc: John Stultz , Thomas Gleixner , Prarit Bhargava , Linux Kernel Subject: [PATCH 10/11] 3.0.x: hrtimer: Update hrtimer base offsets each hrtimer_interrupt Date: Tue, 17 Jul 2012 13:33:57 -0400 Message-Id: <1342546438-17534-11-git-send-email-johnstul@us.ibm.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1342546438-17534-1-git-send-email-johnstul@us.ibm.com> References: <1342546438-17534-1-git-send-email-johnstul@us.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12071717-4242-0000-0000-0000025C3559 X-Gm-Message-State: ALoCoQnaylrH6hcU3qqbS8YaBjlzM1qC0d0pr7zhjPnBJRc03BpuK+GVzivxgCdAOgLePsifRXwt 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 8fc6533..957869f 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;