From patchwork Tue Jul 17 06:39:55 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: john stultz X-Patchwork-Id: 10020 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 79F1E23E56 for ; Tue, 17 Jul 2012 06:40:32 +0000 (UTC) Received: from mail-gg0-f180.google.com (mail-gg0-f180.google.com [209.85.161.180]) by fiordland.canonical.com (Postfix) with ESMTP id 27C90A181CC for ; Tue, 17 Jul 2012 06:40:32 +0000 (UTC) Received: by ggnf1 with SMTP id f1so51840ggn.11 for ; Mon, 16 Jul 2012 23:40:31 -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=f6QVJu9Y4lywoKWAQCkevtNBIbg1AeQt2/fyb3H8FhWFZzQu+2tSWeNGOvHGPA84Qv WoGvRfaNIDp/9/rONmq5b0G2NXN0dG3ZzaImh6EJnnq9v/Ltz/EDZT8UAsyWCwJkT0O5 jdUWTft10wf5/+y9qdtpuej7KJfuEb2i8XDbaKsnQemyY9vf5kXrTTlrQbZal4zU6Wfm 6sMynVZhBNJ3jeEohP5+A5Zejvp4QggKtHaorTHvelvJsp5UlOJ3mxJ9M37KoGaaaTQv BGnmggd2Emqt1tVTLCZV86y8Y1ruLlEqJaOmivsfRK4gnjWHkXGRPk+7Rr2619ge3xV6 dXCQ== Received: by 10.50.87.227 with SMTP id bb3mr381377igb.57.1342507231216; Mon, 16 Jul 2012 23:40:31 -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 lc2csp15737ibb; Mon, 16 Jul 2012 23:40:30 -0700 (PDT) Received: by 10.50.219.194 with SMTP id pq2mr423457igc.25.1342507230342; Mon, 16 Jul 2012 23:40:30 -0700 (PDT) Received: from e2.ny.us.ibm.com (e2.ny.us.ibm.com. [32.97.182.142]) by mx.google.com with ESMTPS id n4si20410092icu.91.2012.07.16.23.40.30 (version=TLSv1/SSLv3 cipher=OTHER); Mon, 16 Jul 2012 23:40:30 -0700 (PDT) Received-SPF: pass (google.com: domain of johnstul@us.ibm.com designates 32.97.182.142 as permitted sender) client-ip=32.97.182.142; Authentication-Results: mx.google.com; spf=pass (google.com: domain of johnstul@us.ibm.com designates 32.97.182.142 as permitted sender) smtp.mail=johnstul@us.ibm.com Received: from /spool/local by e2.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 17 Jul 2012 02:40:29 -0400 Received: from d01dlp01.pok.ibm.com (9.56.224.56) by e2.ny.us.ibm.com (192.168.1.102) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Tue, 17 Jul 2012 02:40:12 -0400 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by d01dlp01.pok.ibm.com (Postfix) with ESMTP id C89C338C803A for ; Tue, 17 Jul 2012 02:40:11 -0400 (EDT) Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q6H6eBJG357310 for ; Tue, 17 Jul 2012 02:40:11 -0400 Received: from d01av01.pok.ibm.com (loopback [127.0.0.1]) by d01av01.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q6HCB4KS020924 for ; Tue, 17 Jul 2012 08:11:04 -0400 Received: from kernel.stglabs.ibm.com (kernel.stglabs.ibm.com [9.114.214.19]) by d01av01.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id q6HCB4cC020889; Tue, 17 Jul 2012 08:11:04 -0400 From: John Stultz To: stable@vger.kernel.org Cc: John Stultz , Thomas Gleixner , Prarit Bhargava , Linux Kernel Subject: [PATCH 6/7] 3.4.x: hrtimer: Update hrtimer base offsets each hrtimer_interrupt Date: Tue, 17 Jul 2012 02:39:55 -0400 Message-Id: <1342507196-54327-7-git-send-email-johnstul@us.ibm.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1342507196-54327-1-git-send-email-johnstul@us.ibm.com> References: <1342507196-54327-1-git-send-email-johnstul@us.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12071706-5112-0000-0000-00000A215821 X-Gm-Message-State: ALoCoQm0OqAB3uyJQ1bQSEYwnIG3uzC4j5EeZVXqt1TnKbTv6/Fa61jyVN3/O7GmbihJVsC/Iwm0 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;