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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 76A76EE6457 for ; Fri, 15 Sep 2023 11:21:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234180AbjIOLVU (ORCPT ); Fri, 15 Sep 2023 07:21:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57328 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231221AbjIOLVR (ORCPT ); Fri, 15 Sep 2023 07:21:17 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6877101; Fri, 15 Sep 2023 04:21:11 -0700 (PDT) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1694776870; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TsnkGbttQgVvHiV9M03Q+LlQoOR8o5QNvoHNuHa+6nY=; b=kUVLHiYJMpOIKyckOH3EGEThs0EpvU+s0q8h8ytzvinMvOtAfd5B7odHXAHSsKB6ibsXQK PnVg39zA19vvSxKixPQ+lABJT51nPvqCctMMvlpaSLwmUt0ComnPBAbfOeDqJkm22KVl5U 69v1YPuRztdswpOaGK+V1mXP6/RYTyNTYTIpwcwlIW6bdb4dXpkVV+7oGssiK5q2PP4b7N S4ApnDPDAMrpld//Dw0tCaKyFut5XTSw4/B2YXE/SrDtZgEkRgbbAd9XRRdohfU850iP1Y sbsq1DHisj/HMJsjV4h+/F/DlveahLIkHgxgeYBSTU+NxAqze0LLubPKBH6ffA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1694776870; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TsnkGbttQgVvHiV9M03Q+LlQoOR8o5QNvoHNuHa+6nY=; b=W6ioBJ1+Iw5AzubKd6BZK7wo1pNLk50251horbdq/DP+xQJ60XUc0+8TacyLFi3g3eztn+ M8sSTyUWXVfOOHCQ== To: Ilpo =?utf-8?Q?J=C3=A4rvinen?= Cc: Greg Kroah-Hartman , Jiri Slaby , linux-serial , Petr Mladek , Thomas Gleixner , LKML , Tony Lindgren , Andy Shevchenko , Florian Fainelli Subject: Re: [PATCH tty v1 06/74] serial: 8250: Use port lock wrappers In-Reply-To: <2045de5e-b7f8-18fe-dc92-e1d88a62f810@linux.intel.com> References: <20230914183831.587273-1-john.ogness@linutronix.de> <20230914183831.587273-7-john.ogness@linutronix.de> <2045de5e-b7f8-18fe-dc92-e1d88a62f810@linux.intel.com> Date: Fri, 15 Sep 2023 13:27:05 +0206 Message-ID: <87y1h7vg0u.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023-09-15, Ilpo J=C3=A4rvinen wrote: >> @@ -3403,9 +3403,9 @@ void serial8250_console_write(struct uart_8250_por= t *up, const char *s, >> touch_nmi_watchdog(); >>=20=20 >> if (oops_in_progress) >> - locked =3D spin_trylock_irqsave(&port->lock, flags); >> + locked =3D uart_port_trylock_irqsave(port, &flags); >> else >> - spin_lock_irqsave(&port->lock, flags); >> + uart_port_lock_irqsave(port, &flags); > > Not related to any problem (with this patch) but I'm a bit curious is > this construct going to remain there after the follow-up work? Yes. The uart port lock already provides excellent coverage of unsafe regions in uart drivers. We want to take advantage of that. > And there's the similar one in some other drivers (with some > variations related to local_irq_save()): > > if (port->sysrq) { > locked =3D 0; > } else if (oops_in_progress) { > locked =3D spin_trylock(&port->lock); > } else { > spin_lock(&port->lock); > locked =3D 1; > } With the follow-up work we are introducing a new type of console (CON_NBCON) that supports atomic and threaded printing. Current console drivers must be converted if they want these features. When converting a driver to NBCON, such variations as above will need to be addressed. The follow-up work provides new functions and semantics to allow drivers to implement more reliable code than just: "trylock and keep going no matter what". For console drivers that are _not_ converted to NBCON, the uart port lock wrappers will not provide any changed functionality. John Ogness