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 1D379C001B0 for ; Fri, 11 Aug 2023 13:50:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235127AbjHKNuU (ORCPT ); Fri, 11 Aug 2023 09:50:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54582 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234398AbjHKNuS (ORCPT ); Fri, 11 Aug 2023 09:50:18 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C23FD18F for ; Fri, 11 Aug 2023 06:50:15 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 6AF381F88C; Fri, 11 Aug 2023 13:50:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1691761814; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=oRJwIFrdoiXP+vzELGTcek+8lDmoluEQ1v+M2HyTAE4=; b=c+lxeGuq4edGXg21rl/8/FQ6+OoqsWh+zeYZGJS7usxWhJEuX4AeHZN/sPCbYNUlfznkjR upuQwJWfnXAn8L0CvUhhyM1+ousfSvOk+Q6agRmnbAV09D3diatZiaFUTBpR2Zj2qahmet y6tp8xopfxDS95niqtGeTnZZipOD3fM= Received: from suse.cz (unknown [10.100.201.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 39DAB2C142; Fri, 11 Aug 2023 13:50:14 +0000 (UTC) Date: Fri, 11 Aug 2023 15:50:10 +0200 From: Petr Mladek To: John Ogness Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, Greg Kroah-Hartman Subject: Re: [PATCH printk v2 8/8] printk: nbcon: Add functions for drivers to mark unsafe regions Message-ID: References: <20230728000233.50887-1-john.ogness@linutronix.de> <20230728000233.50887-9-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230728000233.50887-9-john.ogness@linutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 2023-07-28 02:08:33, John Ogness wrote: > From: Thomas Gleixner > > For the write_atomic callback, the console driver may have unsafe > regions that need to be appropriately marked. Provide functions > that accept the nbcon_write_context struct to allow for the driver > to enter and exit unsafe regions. > > diff --git a/kernel/printk/printk_nbcon.c b/kernel/printk/printk_nbcon.c > index e1f0e4278ffa..57b7539bbbb2 100644 > --- a/kernel/printk/printk_nbcon.c > +++ b/kernel/printk/printk_nbcon.c > @@ -761,7 +761,6 @@ EXPORT_SYMBOL_GPL(nbcon_can_proceed); > * > * Internal helper to avoid duplicated code > */ > -__maybe_unused > static bool nbcon_context_update_unsafe(struct nbcon_context *ctxt, bool unsafe) > { > struct console *con = ctxt->console; It might be better to define nbcon_context_update_unsafe() in this patch. I guess that nbcon_enter_unsafe()/nbcon_exit_unsafe() are the only callers. > @@ -787,6 +786,46 @@ static bool nbcon_context_update_unsafe(struct nbcon_context *ctxt, bool unsafe) > return true; > } > > +/** > + * nbcon_enter_unsafe - Enter an unsafe region in the driver > + * @wctxt: The write context that was handed to the write function > + * > + * Return: True if the state is correct. False if ownership was > + * handed over or taken. Same as in 7th patch. I would write: * Return: True if this context still owns the console. False if the ownership has been handed over or taken. > + * > + * When this function returns false then the calling context is no longer > + * the owner and is no longer allowed to go forward. In this case it must > + * back out immediately and carefully. The buffer content is also no longer > + * trusted since it no longer belongs to the calling context. > + */ > +bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt) > +{ > + struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt); > + > + return nbcon_context_update_unsafe(ctxt, true); > +} > +EXPORT_SYMBOL_GPL(nbcon_enter_unsafe); > + > +/** > + * nbcon_exit_unsafe - Exit an unsafe region in the driver > + * @wctxt: The write context that was handed to the write function > + * > + * Return: True if the state is correct. False if ownership was > + * handed over or taken. Same here. > + * When this function returns false then the calling context is no longer > + * the owner and is no longer allowed to go forward. In this case it must > + * back out immediately and carefully. The buffer content is also no longer > + * trusted since it no longer belongs to the calling context. > + */ > +bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) > +{ > + struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt); > + > + return nbcon_context_update_unsafe(ctxt, false); > +} > +EXPORT_SYMBOL_GPL(nbcon_exit_unsafe); > + Best Regards, Petr