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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C1522D2F34B for ; Tue, 13 Jan 2026 17:37:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=/CVOy4tPw1zWY0e6rYcKRwtfrfRvUlKFzd8YTNoGp5w=; b=K0VnHvtNa4xi9UWLCgWju7vRX9 ns4xTNPRBtM1PIDFi2UQudcgm9mZMYTskCSZY3F7+pXM0Ft9Kou8AiAtt+6D1HOfIQtzdFWC6acSI ubr0QRETHkeT1DfsbYWAiBkpldNuZ2xukSYMR0Vx+Ck2A6kpZ73YA0crY5Rz5pzJH38BPt+xkxdKL DeBgxxD35RudbhfpR3iMmAn3tZnoPyGqsH6TvnXKqCbzgHofRAFPs8bLuJbv7xQ+t5aFRVoNFtYnO u3IXj4guvIsExcYUShlus59t2YOwPwpBigAqrSil544u+4Vw8h9K9nwnbtxTkkKSvRXxI4Bx2YD/t h6sqS0Xg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vfiKa-00000007Xfb-1jeq; Tue, 13 Jan 2026 17:37:24 +0000 Received: from mail-wr1-x434.google.com ([2a00:1450:4864:20::434]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vfiKY-00000007Xef-1W8E for linux-arm-kernel@lists.infradead.org; Tue, 13 Jan 2026 17:37:23 +0000 Received: by mail-wr1-x434.google.com with SMTP id ffacd0b85a97d-430f57cd471so3943958f8f.0 for ; Tue, 13 Jan 2026 09:37:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1768325840; x=1768930640; darn=lists.infradead.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=/CVOy4tPw1zWY0e6rYcKRwtfrfRvUlKFzd8YTNoGp5w=; b=RI06ZjcUx2YgRorbLPOXIHkMJV7NvKIDeapH0PXsXWGP3eMuP7Y5jNic434/mVF9w/ Uss3hnZZlE+8HCBjbHgyuvmnu7b9lgnvFTqlgQjs2aFVRjelsabhvX/+KRo7OrXU2tkv 7i7/NKxX/CPUjIsAvUNoeOHQO5K1HLUd1xmWor9o93OMk9Wi1kS00vLq7f8meA0xMgwJ +4Jzw2w1W1O0OY2lTlbe7ByPIBTn540eQwOHGkMBm3WcVpZkAdWCE7ISNLPr0ljAfiSt l8DFLROXSZ9OGErfxpIb3trC+WGD/6dTel4eTzQTyBQ0m0kYm7GPHbpW1CH2AdWDVzXt blJw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1768325840; x=1768930640; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=/CVOy4tPw1zWY0e6rYcKRwtfrfRvUlKFzd8YTNoGp5w=; b=T2TSAB+1UsWfC6KXgSAN4GT/liyVKboa0aNzIbM+sdhqcLFglI6yjykPMnBqUJ+5l7 7aR48sZsy6l0GcEpJWrqa5Dh4sbaXUm4Xta+fBg//PWv6AO70bVwX+xxvZueMglwVOEX RcfL7IOJm3cdi3Xj1tS9VsyctLu6lEIA+dvG6Re0GNtuhwi0EHIu1pODFlN1pLl/jt5Z vVLbJSpAZkgtx0MvqTED/R6lRfP19TIsGEIxi5QghlLCm1czaEMN4lqDTEKliRsokraT flYDwUTn1EZO1R8IampQYSSo46rwbecf/Ycf2b5o8oM8LErEwJ274Sl76boUaomUTecm BOQg== X-Forwarded-Encrypted: i=1; AJvYcCXTrM7DMEEsNC8I67VzrKVrnV1CTJ1WjX7lkELtqbBKZVnUyaCwBAjM+prFeNotHuqAhM8Bfu2I2oDN0oZAgQb2@lists.infradead.org X-Gm-Message-State: AOJu0YxwgKt6oQ6sfKKW5eE9+J2S/GE7AjSKeXnc1zCgMTT4YWY3meuk kreIoD+OTLRWe9QljbdlBR1O7Bf1rwMkBtHTBMK0dTodIv4NSNaUjVXF0t+1CBBty4A= X-Gm-Gg: AY/fxX4t1iw03MzGr888KHEaIuZnSweav7jsc+ctGAX1ZAnXn3wWRDgO1THMR3SHi6t i4l+V2GL1ToGut7GyN+Ap6GfDnE94YFgSEb3LDkZXoYlcmj4bBIGOfuiFrsvafT2jpXfuWwfq3w rbDXgg8ycDz5JIXkn18zo7fkduZZXxei/o/GIvp/2lJbuDonojEWmI5twDwijuTdzyLtoYwe4QW D3iPNHjyxHDUekXijklLfT6Ht00nLGeijx4PXG26JUCaV13Yu2qxKvOAzgVlh8Xo4RUoKi5KYop bPFYIGx4ZFK6TahQ7PtZFLwB5l9C0PPdGAo4mjbRxvuJm7bsIywep//dCHT4LhaITrHYlSuaunJ r4/qydLcbdiJN/C15nnqXGwr9NwgHkhoT3Y9KFbv3M+CFRdWmgjLYwvEI94QbuVQjiOZ2adTTag c9jKlpuPJdlBVeLw== X-Google-Smtp-Source: AGHT+IHUReQqvVgC0db5F0/UgqAPwHgCcpq2ZD0lhm0g7XnDeEa3Phlj1/GEitKl8zvqkUFbSZC6XA== X-Received: by 2002:a05:6000:2dc9:b0:430:fced:902 with SMTP id ffacd0b85a97d-432c36436fbmr29258778f8f.26.1768325840268; Tue, 13 Jan 2026 09:37:20 -0800 (PST) Received: from pathway.suse.cz ([176.114.240.130]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-432d9610671sm28342147f8f.34.2026.01.13.09.37.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Jan 2026 09:37:19 -0800 (PST) Date: Tue, 13 Jan 2026 18:37:17 +0100 From: Petr Mladek To: Marcos Paulo de Souza Cc: Richard Weinberger , Anton Ivanov , Johannes Berg , Greg Kroah-Hartman , Jason Wessel , Daniel Thompson , Douglas Anderson , Steven Rostedt , John Ogness , Sergey Senozhatsky , Jiri Slaby , Breno Leitao , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Geert Uytterhoeven , Kees Cook , Tony Luck , "Guilherme G. Piccoli" , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Andreas Larsson , Alexander Shishkin , Maxime Coquelin , Alexandre Torgue , Jacky Huang , Shan-Chun Hung , Laurentiu Tudor , linux-um@lists.infradead.org, linux-kernel@vger.kernel.org, kgdb-bugreport@lists.sourceforge.net, linux-serial@vger.kernel.org, netdev@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-hardening@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 02/19] printk: Introduce console_is_nbcon Message-ID: References: <20251227-printk-cleanup-part3-v1-0-21a291bcf197@suse.com> <20251227-printk-cleanup-part3-v1-2-21a291bcf197@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251227-printk-cleanup-part3-v1-2-21a291bcf197@suse.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260113_093722_428005_B05B2D0E X-CRM114-Status: GOOD ( 31.88 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sat 2025-12-27 09:16:09, Marcos Paulo de Souza wrote: > Besides checking if the current console is NBCON or not, console->flags > is also being read in order to serve as argument of the console_is_usable > function. > > But CON_NBCON flag is unique: it's set just once in the console > registration and never cleared. In this case it can be possible to read > the flag when console_srcu_lock is held (which is the case when using > for_each_console). > > This change makes possible to remove the flags argument from > console_is_usable in the next patches. > > Signed-off-by: Petr Mladek > Signed-off-by: Marcos Paulo de Souza > --- > include/linux/console.h | 27 +++++++++++++++++++++++++++ > kernel/debug/kdb/kdb_io.c | 2 +- > kernel/printk/nbcon.c | 2 +- > kernel/printk/printk.c | 15 ++++++--------- > 4 files changed, 35 insertions(+), 11 deletions(-) > > diff --git a/include/linux/console.h b/include/linux/console.h > index 35c03fc4ed51..dd4ec7a5bff9 100644 > --- a/include/linux/console.h > +++ b/include/linux/console.h > @@ -561,6 +561,33 @@ static inline void console_srcu_write_flags(struct console *con, short flags) > WRITE_ONCE(con->flags, flags); > } > > +/** > + * console_srcu_is_nbcon - Locklessly check whether the console is nbcon There is _srcu in the function name, see below. > + * @con: struct console pointer of console to check > + * > + * Requires console_srcu_read_lock to be held, which implies that @con might > + * be a registered console. The purpose of holding console_srcu_read_lock is > + * to guarantee that no exit/cleanup routines will run if the console > + * is currently undergoing unregistration. > + * > + * If the caller is holding the console_list_lock or it is _certain_ that > + * @con is not and will not become registered, the caller may read > + * @con->flags directly instead. > + * > + * Context: Any context. > + * Return: True when CON_NBCON flag is set. > + */ > +static inline bool console_is_nbcon(const struct console *con) And here it is without _srcu. I would prefer the variant with _srcu to make it clear that it can be called only under _srcu. Similar to console_srcu_read_flags(con). > +{ > + WARN_ON_ONCE(!console_srcu_read_lock_is_held()); > + > + /* > + * The CON_NBCON flag is statically initialized and is never > + * set or cleared at runtime. > + */ > + return data_race(con->flags & CON_NBCON); > +} > + > /* Variant of console_is_registered() when the console_list_lock is held. */ > static inline bool console_is_registered_locked(const struct console *con) > { Otherwise, it looks good to me. With a consistent name, feel free to use: Reviewed-by: Petr Mladek Best Regards, Petr