From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 034AC367B95; Tue, 2 Jun 2026 10:56:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780397813; cv=none; b=G1czflpAWbClfX3Ef+gF53u2GKYuifpcTtw79wxlprRlw/a0xQxOXtuAcD4m6nzH8qjcrHee5X4CD6r/ENshWF8k7+wd4hMdfOLXjakBoFaFpuq6BcQ0aroYYwAlpz4kYq0cy590TffIU4sFPZFEqyowvq5kdypxuxvN3/9x0D4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780397813; c=relaxed/simple; bh=SDInTYX8ts6pFvijGaniL/u/sVVBMbKniwF4IDdTF4c=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=MJ8MAC4WJcKWexebSgbKkxoX1qUBOntT7lbbJBlbfOB+6EmlodITFBXcQO1/tXpO+ErflCsgZzO1EDMratPbaF6x0p+99C0fG0l7nrplaxjJI3hcGtCZO7P8IQAPOUHnPppuVjLOdzQEDjzxB75Jbr3kZaQlP/EkWj+dnfWnNUk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=casper.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=FuH2WRyu; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=casper.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="FuH2WRyu" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=kD2nMuipcJrgnsCHjq6fWZ5/WZID4hwcULnwIDazjr4=; b=FuH2WRyu9p7SDZz8zDQWYtzhXz 5piRa9cAmYI6NbLHprb4qgbZYVssIqNsrTKyM2amSRiXgiUngfh7aL/ZnVRD7iDb9uCRh943Q1egI j9vkz+BbL9SjHswTTcdAtG1Nd1qKgXy1Nhdp24zCoP3OBy2p3mwhGeQ64tlXsnkHo+A/DpQLt3eOD 7LZMVNnMPXHg7AEi7MQQd66xBD0NrS8twzpHP/vjMf8k9/u4sAJDEfW+h98hSw5NxPfWqpYD9XKUW 6KYeLJ4P5o7bGEmByqkcpKEwQyd+35wlaO+SHwVYnerzqIuqEPyOTdFUFwI4uWRgut9jrhLzjXo6V v0pvoSGA==; Received: from [2001:8b0:10b:5:5b40:b57d:669c:36f4] (helo=u09cd745991455d.ant.amazon.com) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wUMnc-00000001oau-01TD; Tue, 02 Jun 2026 10:56:44 +0000 Message-ID: <69ae007149c7b29331ede633fbd6fa92e3cae9b4.camel@infradead.org> Subject: Re: [patch V2 04/25] pps: Convert to ktime_get_snapshot_id() From: David Woodhouse To: Thomas Gleixner , Rodolfo Giometti , LKML Cc: Miroslav Lichvar , John Stultz , Stephen Boyd , Anna-Maria Behnsen , Frederic Weisbecker , thomas.weissschuh@linutronix.de, Arthur Kiyanovski , Vincent Donnefort , Marc Zyngier , Oliver Upton , kvmarm@lists.linux.dev, Oliver Upton , Richard Cochran , netdev@vger.kernel.org, Takashi Iwai , Miri Korenblit , Johannes Berg , Jacob Keller , Tony Nguyen , Saeed Mahameed , Peter Hilber , "Michael S. Tsirkin" , virtualization@lists.linux.dev, linux-wireless@vger.kernel.org, linux-sound@vger.kernel.org, Vadim Fedorenko Date: Tue, 02 Jun 2026 11:56:43 +0100 In-Reply-To: <877boh8f0j.ffs@fw13> References: <20260529193435.921555544@kernel.org> <20260529195557.123410250@kernel.org> <912a22e8-878f-4763-958b-71052ee69b36@enneenne.com> <877boh8f0j.ffs@fw13> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-ocxyGnVSTJWlICdoO5wX" User-Agent: Evolution 3.52.3-0ubuntu1.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html --=-ocxyGnVSTJWlICdoO5wX Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2026-06-02 at 11:31 +0200, Thomas Gleixner wrote: > On Sat, May 30 2026 at 13:08, Rodolfo Giometti wrote: > > On 29/05/2026 22:00, Thomas Gleixner wrote: > > > =C2=A0=C2=A0 static inline void pps_get_ts(struct pps_event_time *ts) > > > =C2=A0=C2=A0 { > > > +#ifdef CONFIG_NTP_PPS > > > =C2=A0=C2=A0=C2=A0 struct system_time_snapshot snap; > > > =C2=A0=C2=A0=20 > > > - ktime_get_snapshot(&snap); > > > - ts->ts_real =3D ktime_to_timespec64(snap.real); > > > -#ifdef CONFIG_NTP_PPS > > > - ts->ts_raw =3D ktime_to_timespec64(snap.raw); > > > + ktime_get_snapshot_id(CLOCK_REALTIME, &snap); > > > + ts->ts_real =3D ktime_to_timespec64(snap.systime); > > > + ts->ts_raw =3D ktime_to_timespec64(snap.monoraw); > > > +#else > > > + ktime_get_real_ts64(&ts->ts_real); > >=20 > > =C2=A0 /* > > =C2=A0 * Prevent kernel stack information disclosure if the > > =C2=A0 * structure is later copied to userspace. > > =C2=A0 */ > > =C2=A0 ts->ts_raw =3D (struct timespec64){0, 0}; >=20 > Which will fail to build because of: >=20 > struct pps_event_time { > #ifdef CONFIG_NTP_PPS > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct timespec64 ts_raw; > #endif /* CONFIG_NTP_PPS */ > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct timespec64 ts_real; > }; >=20 > No? I think we should kill struct pps_event_time and just use a system_time_snapshot anyway. And I think we can make CONFIG_NTP_PPS work for NOHZ too. If I understand correctly, the main problem with NOHZ is that without a tick, the reported CLOCK_REALTIME sawtooths much more around the time that the core timekeeping *wants* to report. That is, tk->ntp_error goes much higher and much lower, than when the precise 'mult' rate can be re-adjusted every tick to keep it on course. If we add an ntp_error field to the system_time_snapshot, the PPS code could use that to correct the CLOCK_REALTIME value and the jitter that NOHZ introduces wouldn't matter. --=-ocxyGnVSTJWlICdoO5wX Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCD9Aw ggSOMIIDdqADAgECAhAOmiw0ECVD4cWj5DqVrT9PMA0GCSqGSIb3DQEBCwUAMGUxCzAJBgNVBAYT AlVTMRUwEwYDVQQKEwxEaWdpQ2VydCBJbmMxGTAXBgNVBAsTEHd3dy5kaWdpY2VydC5jb20xJDAi BgNVBAMTG0RpZ2lDZXJ0IEFzc3VyZWQgSUQgUm9vdCBDQTAeFw0yNDAxMzAwMDAwMDBaFw0zMTEx MDkyMzU5NTlaMEExCzAJBgNVBAYTAkFVMRAwDgYDVQQKEwdWZXJva2V5MSAwHgYDVQQDExdWZXJv a2V5IFNlY3VyZSBFbWFpbCBHMjCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAMjvgLKj jfhCFqxYyRiW8g3cNFAvltDbK5AzcOaR7yVzVGadr4YcCVxjKrEJOgi7WEOH8rUgCNB5cTD8N/Et GfZI+LGqSv0YtNa54T9D1AWJy08ZKkWvfGGIXN9UFAPMJ6OLLH/UUEgFa+7KlrEvMUupDFGnnR06 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