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[209.132.180.67]) by mx.google.com with ESMTP id a11si401359pga.198.2019.02.04.08.26.05; Mon, 04 Feb 2019 08:26:08 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=gmZuOKV+; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731224AbfBDQ0D (ORCPT + 31 others); Mon, 4 Feb 2019 11:26:03 -0500 Received: from mail-wr1-f65.google.com ([209.85.221.65]:45716 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729761AbfBDQ0A (ORCPT ); Mon, 4 Feb 2019 11:26:00 -0500 Received: by mail-wr1-f65.google.com with SMTP id q15so433554wro.12 for ; Mon, 04 Feb 2019 08:25:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=uh0mWn8UrzjjJpP8IvQQtBqJhS8PhQJ/5HnUmOlZIks=; b=gmZuOKV+QFRNuw7Xiq01qUxU2MZBcpwkazl6G5C+h5WY9pAGCiz91/y7DoyN/0jhFY DZ8i3Vafab444Z0m63eLyReMXiadyi2xz0C+aOngk/lRbyG81BWpa+kBRlKmiLkPSDct YfqFD1w+6asWT2k4jairtsCwvVi474zCNUtO0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=uh0mWn8UrzjjJpP8IvQQtBqJhS8PhQJ/5HnUmOlZIks=; b=gzoVrM1yc9LpplA4RMvambaHynufPg15jBfAWNsft8JU7CCoN4HDXzNzMZvFu+D5zH 9Gl2coNxmaBjMxyNFyXqPJkszcZpNPslWs275Zc0KDxZCUWfgImuObW4vMvuL/R9jG3X nS6nbs7LdWaHrc7dJThwic3HAElNEhZOoW7jDWyWIKex6JgrpvmKfumiLsOiOIsPY6S1 FsxllZdT0Bs72kdZOVYuErBeINa7rHHzTf9uMUDXPtf5Un+WZx6IzFCg6Y+TkFquszqQ eubPnSqXBokWugqcPEcEJEMppLHBBnSG0RlJXUWaOa+jWfEPz/taDBWeka7sjusf7uzS vimQ== X-Gm-Message-State: AHQUAubYTiyMRJ/BftIvnJdW67CLvWIS8L2XyFR3uB2FClzx9+IJoLMp GwlL2Js+glM3l7uLKCZTYOMIJw== X-Received: by 2002:a5d:6aca:: with SMTP id u10mr148455wrw.310.1549297558732; Mon, 04 Feb 2019 08:25:58 -0800 (PST) Received: from localhost.localdomain ([2a01:e0a:f:6020:70b6:b9c6:89e2:36a]) by smtp.gmail.com with ESMTPSA id a4sm1251992wrt.37.2019.02.04.08.25.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 04 Feb 2019 08:25:57 -0800 (PST) From: Vincent Guittot To: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, rjw@rjwysocki.net, ulf.hansson@linaro.org, biju.das@bp.renesas.com Cc: linux-arm-kernel@lists.infradead.org, geert@linux-m68k.org, thara.gopinath@linaro.org, linux-renesas-soc@vger.kernel.org, Vincent Guittot Subject: [PATCH 1/2] PM-runtime: move runtime accounting on ktime_get_mono_fast_ns() Date: Mon, 4 Feb 2019 17:25:52 +0100 Message-Id: <1549297553-17647-2-git-send-email-vincent.guittot@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1549297553-17647-1-git-send-email-vincent.guittot@linaro.org> References: <1549297553-17647-1-git-send-email-vincent.guittot@linaro.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Similarly to what happened whith autosuspend, a deadlock has been raised with runtime accounting in the sequence: change_clocksource ... write_seqcount_begin ... timekeeping_update ... sh_cmt_clocksource_enable ... rpm_resume update_pm_runtime_accounting ktime_get do read_seqcount_begin while read_seqcount_retry .... write_seqcount_end Move runtime accounting on ktime_get_mono_fast_ns() With ktime_get_mono_fast_ns, the timestamp is not guaranteed to be monotonic across an update of timekeeping and as a result time can goes backward. Add a test to skip accounting for such situation which should stay exceptional. Fixes: a08c2a5a3194 ("PM-runtime: Replace jiffies-based accounting with ktime-based accounting") Reported-by: Biju Das Signed-off-by: Vincent Guittot --- drivers/base/power/runtime.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) -- 2.7.4 diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 1caa394..50740da 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -66,13 +66,22 @@ static int rpm_suspend(struct device *dev, int rpmflags); */ void update_pm_runtime_accounting(struct device *dev) { - u64 now = ktime_to_ns(ktime_get()); + u64 now = ktime_get_mono_fast_ns(); + u64 last = dev->power.accounting_timestamp; u64 delta; - delta = now - dev->power.accounting_timestamp; - dev->power.accounting_timestamp = now; + /* + * Because ktime_get_mono_fast_ns() is not monotonic during + * timekeeping update, we must ensure that now is after the last saved + * timesptamp + */ + if (now < last) + return; + + delta = now - last; + if (dev->power.disable_depth > 0) return; @@ -1312,7 +1321,7 @@ void pm_runtime_enable(struct device *dev) /* About to enable runtime pm, set accounting_timestamp to now */ if (!dev->power.disable_depth) - dev->power.accounting_timestamp = ktime_to_ns(ktime_get()); + dev->power.accounting_timestamp = ktime_get_mono_fast_ns(); } else { dev_warn(dev, "Unbalanced %s!\n", __func__); }