From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 72774C43144 for ; Mon, 25 Jun 2018 14:38:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2195E25B93 for ; Mon, 25 Jun 2018 14:38:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="QsipTKrb"; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="PF5NHaUY" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2195E25B93 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934426AbeFYOiY (ORCPT ); Mon, 25 Jun 2018 10:38:24 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:45070 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934255AbeFYOiW (ORCPT ); Mon, 25 Jun 2018 10:38:22 -0400 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 0C899607EB; Mon, 25 Jun 2018 14:38:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1529937502; bh=RKTkE/Zd7Ena1Eu/mNuudsmwbEvsSuGs5VPkan1DAn8=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=QsipTKrb0H5kdR9ACTxhWboGM3Ne1NThHQFDyowlT10zGH6qRK68eNOIkS1UKRxgV gzliFrZRI5c4mjOPe8wTn/1nKVaM3qYTC3kvyvHn6p+dgtkg7Npukt+o8XgABVguKi l08BPLrW/Upy9cYBCV/kMpnLy6OE5U/BkxMq+EEU= Received: from [10.204.79.100] (blr-c-bdr-fw-01_globalnat_allzones-outside.qualcomm.com [103.229.19.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: mojha@smtp.codeaurora.org) by smtp.codeaurora.org (Postfix) with ESMTPSA id 3D0EC60376; Mon, 25 Jun 2018 14:38:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1529937500; bh=RKTkE/Zd7Ena1Eu/mNuudsmwbEvsSuGs5VPkan1DAn8=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=PF5NHaUYIQjXZw26trACD1tEMgO4rIlVp0W8cEBBNW/KjC+fGa4W+4IJ1/4xDbp5X WEZFnHDcXKI8x9TmRnQyUvPf/9OwpvSA1bTY06caSQgATQjzO+OEnm3eo10Dk5zvqD 89JlxZ7mYrm2tgD6IBSx2zMVsDGiSpVoiDswyrXI= DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 3D0EC60376 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=mojha@codeaurora.org Subject: Re: [PATCH v2] time: Fix sleeptime injection for non-stop clocksource & persistent clock To: Thomas Gleixner Cc: john.stultz@linaro.org, linux-kernel@vger.kernel.org, neeraju@codeaurora.org, gkohli@codeaurora.org, cpandya@codeaurora.org References: <1527680699-16068-1-git-send-email-mojha@codeaurora.org> From: Mukesh Ojha Message-ID: Date: Mon, 25 Jun 2018 20:08:13 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Thomas, Thanks you very much for your time and reply. On 6/23/2018 2:57 AM, Thomas Gleixner wrote: > On Wed, 30 May 2018, Mukesh Ojha wrote: >> Currently, for both non-stop clocksource and persistent clock >> there is a corner case, when a driver failed to go suspend mode. >> rtc_resume() injects the sleeptime as timekeeping_rtc_skipresume() >> returned 'false'(sleeptime_injected=false) due to which we can >> see mismatch in timestamps between system clock and other timers. >> >> Fix this by updating sleeptime_injected=true for both non-stop >> clocksource and persistent clock. >> >> Success case: >> ------------ >> {sleeptime_injected=true} >> rtc_suspend() => timekeeping_suspend() => timekeeping_resume() => >> rtc_resume() >> >> Failure case: >> ------------ >> {failure in sleep path} {sleeptime_injected=false} >> rtc_suspend() => rtc_resume() > I can see the problem. > >> Signed-off-by: Mukesh Ojha >> --- >> Changes in v2: >> * Updated the commit text. >> * Removed extra variable and used the earlier static >> variable 'sleeptime_injected'. >> >> kernel/time/timekeeping.c | 11 +++++++++++ >> 1 file changed, 11 insertions(+) >> >> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c >> index 49cbcee..2754c1b 100644 >> --- a/kernel/time/timekeeping.c >> +++ b/kernel/time/timekeeping.c >> @@ -1610,6 +1610,17 @@ static void __timekeeping_inject_sleeptime(struct timekeeper *tk, >> */ >> bool timekeeping_rtc_skipresume(void) >> { >> + struct timekeeper *tk = &tk_core.timekeeper; >> + /* >> + * This is to ensure that we don't end up injecting >> + * the sleeptime via rtc_resume() for non-stop clocksource >> + * when we fail to sleep. >> + */ >> + if (!sleeptime_injected) >> + sleeptime_injected = ((tk->tkr_mono.clock->flags & >> + CLOCK_SOURCE_SUSPEND_NONSTOP) || >> + (persistent_clock_exists)) ? true : false; > But this is really a horrible hack. The right thing to do is to keep track > whether timekeeping_suspend() has been reached in the first place. There is > a very simple way to do that. Uncompiled and completely untested patch > below, but you get the idea. Yeah, missed completely the fact that the issue can also come where only clocksource is RTC. > Thanks, > > tglx > > 8<------------------- > diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c > index 4786df904c22..32ae9aea61c3 100644 > --- a/kernel/time/timekeeping.c > +++ b/kernel/time/timekeeping.c > @@ -1510,8 +1510,20 @@ void __weak read_boot_clock64(struct timespec64 *ts) > ts->tv_nsec = 0; > } > > -/* Flag for if timekeeping_resume() has injected sleeptime */ > -static bool sleeptime_injected; > +/* > + * Flag reflecting whether timekeeping_resume() has injected sleeptime. > + * > + * The flag starts of true and is only cleared when a suspend reaches > + * timekeeping_suspend(), timekeeping_resume() sets it when the timekeeper > + * clocksource is not stopping across suspend and has been used to update > + * sleep time. If the timekeeper clocksource has stopped then the flag > + * stays false and is used by the RTC resume code to decide whether sleep > + * time must be injected and if so the flag gets set then. > + * > + * If a suspend fails before reaching timekeeping_resume() then the flag > + * stays true and prevents erroneous sleeptime injection. > + */ > +static bool sleeptime_injected = true; This will prevent first sleep failure. > > /* Flag for if there is a persistent clock on this platform */ > static bool persistent_clock_exists; > @@ -1646,6 +1658,8 @@ void timekeeping_inject_sleeptime64(struct timespec64 *delta) > raw_spin_lock_irqsave(&timekeeper_lock, flags); > write_seqcount_begin(&tk_core.seq); > > + sleeptime_injected = true; This will prevent further extra sleeptime injection if sleep fails (valid for RTC only). Looks good! > + > timekeeping_forward_now(tk); > > __timekeeping_inject_sleeptime(tk, delta); > @@ -1671,7 +1685,6 @@ void timekeeping_resume(void) > struct timespec64 ts_new, ts_delta; > u64 cycle_now; > > - sleeptime_injected = false; > read_persistent_clock64(&ts_new); > > clockevents_resume(); > @@ -1743,6 +1756,8 @@ int timekeeping_suspend(void) > if (timekeeping_suspend_time.tv_sec || timekeeping_suspend_time.tv_nsec) > persistent_clock_exists = true; > > + sleeptime_injected = false; I did not get the exact valid point of moving it from `timekeeping_suspend` to `timekeeping_resume`. Although it will not have any side effect. > + > raw_spin_lock_irqsave(&timekeeper_lock, flags); > write_seqcount_begin(&tk_core.seq); > timekeeping_forward_now(tk); > Thanks for the change;  will check and update. Cheers, Mukesh