From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lf1-f45.google.com (mail-lf1-f45.google.com [209.85.167.45]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8C4085674E for ; Thu, 14 Nov 2024 16:51:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.45 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731603116; cv=none; b=gr2apg2qM1cUfV0kjrCsMiEa+6DghWAce9mRgwnkvhcueKTkF6ulps+tPLml12z1aqgfoB37yrA/mPHDDRZAKgBTqbkgi5xY53IPBfNCD2KY3ANGaiM8Ojo1McZ7QjKULgrkSo/nmtgJiC/ZWR5xzNMBJO75KlQxzmf0rk4xBeY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731603116; c=relaxed/simple; bh=NszP7TXqWj2S/e1y5AGoZZXxdUD7VRLHgXHhDIJdk/g=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ty914fEV+mTz1MpQVQD6gTuBpMyseyXYL8KISQOL0zCNDBc/X8srL3gO+a5uW/kn7qj6QzUxGreNtC2MhKtSrzD3G0JeynEHXpQqHMBTQOND+PWx7nCcj58sW39xB9tyNdchD20CZX6vW1sbe3Vka8Z9XAvpEEMhVCd0JsKKkzc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com; spf=pass smtp.mailfrom=suse.com; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b=XuSh+hJ3; arc=none smtp.client-ip=209.85.167.45 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b="XuSh+hJ3" Received: by mail-lf1-f45.google.com with SMTP id 2adb3069b0e04-53da5a27771so916639e87.2 for ; Thu, 14 Nov 2024 08:51:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1731603112; x=1732207912; darn=vger.kernel.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=r4wPxzflWKzXhO1nuki36dNsr0Nxtgqzfwxp448aaNk=; b=XuSh+hJ3BGbYUeccL2/nKRSJ1Adx7uZJDUUGV0wE4hFTIaN/VGzdG2rBxs7i7eNFLd XThv9YlTTgm3NkT4ArrSvMb7hBwy2kctE9X6BxT9bdlGfZkszXYfw7+f/uWVBvpW8Xua BFP/8aDsUpVUpUcdf2t2gxwsp5/QmT4jgOgY8M14eOc65dt8/GfE8mq1JT8XA89+Ravc Rq43UiEB9Ry+UtVw/RQucEkVjplQ133D4tXgRsJ5kH9y9SClTSvSAKj1hq99uS1U+J3O HA/G0lPqTup3wFQxGEXoewfOuciKD941JnJC4hk0VDuC8wkK1m1Sr1HxJQeM+837PnBO 6Gtw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1731603112; x=1732207912; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=r4wPxzflWKzXhO1nuki36dNsr0Nxtgqzfwxp448aaNk=; b=Os9d9S0hhNrjmx+pxSEr9bVZjSPXqoPJB2e54nfXhejMdo/dB/OPlCN68yLpSDZmwL BuB9fLA31CbS6/eREf8PkFNgJLIOWQWqM1MuT1tsKYakuGaZ5LlRhLYtnDCayXczVm9Y vUWm7DBE4M+nSAL4iwrumVa9wE/VT5T0j9AGrNNePwijZqhLDSFhneAaIjawMFEIurDt IuLiY1gIo/sfiDdbiqeMFyOavgWTiJjOt8nCGOF5pmdUrinkUPQ5B8aKu31wxgIb0JaS YbeJ5nG5GHJmJnltR/nD2Di06fGBJNMmaM6e5LtMNlJTHuQzlckkhqBfPRACOywbg9Na +4+g== X-Gm-Message-State: AOJu0Yx5GY42ZFUuBmXsCtwV9Y6Bs3/+GTHYnBpPwl8JAa5csif4E1G2 hZNKsH5Ifit5iQT/mnOjjAcQjKLsAKDEwN55sNjlkYn8GPRC1oN0Sk6CmXxyvgE= X-Google-Smtp-Source: AGHT+IEMRk4K0IqzRtS7aXdMxOPTIt1tDe0rMCW0UzLZAOSPvPDT+yjHwx6FIDbxBGBgADbKY/PlSQ== X-Received: by 2002:a05:6512:224e:b0:53d:a2e2:5877 with SMTP id 2adb3069b0e04-53da5c28cabmr1499944e87.5.1731603112347; Thu, 14 Nov 2024 08:51:52 -0800 (PST) Received: from pathway.suse.cz ([176.114.240.50]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-432dab806e1sm26954855e9.20.2024.11.14.08.51.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Nov 2024 08:51:51 -0800 (PST) Date: Thu, 14 Nov 2024 17:51:49 +0100 From: Petr Mladek To: Chris Down Cc: linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Sergey Senozhatsky , Steven Rostedt , John Ogness , Geert Uytterhoeven , Tony Lindgren , kernel-team@fb.com Subject: Re: [PATCH v6 03/11] printk: console: Implement core per-console loglevel infrastructure Message-ID: References: <28d8dff56bc15b2a41f0d2035701ccb11df22610.1730133890.git.chris@chrisdown.name> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri 2024-11-08 17:10:31, Petr Mladek wrote: > On Mon 2024-10-28 16:45:37, Chris Down wrote: > > Consoles can have vastly different latencies and throughputs. For > > example, writing a message to the serial console can take on the order > > of tens of milliseconds to get the UART to successfully write a message. > > While this might be fine for a single, one-off message, this can cause > > significant application-level stalls in situations where the kernel > > writes large amounts of information to the console. > > > > --- a/drivers/tty/sysrq.c > > +++ b/drivers/tty/sysrq.c > > @@ -101,11 +102,25 @@ __setup("sysrq_always_enabled", sysrq_always_enabled_setup); > > static void sysrq_handle_loglevel(u8 key) > > { > > u8 loglevel = key - '0'; > > + int cookie; > > + int warned = 0; > > + struct console *con; > > > > console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; > > pr_info("Loglevel set to %u\n", loglevel); > > console_loglevel = loglevel; > > + > > + cookie = console_srcu_read_lock(); > > + for_each_console_srcu(con) { > > + if (!warned && per_console_loglevel_is_set(con)) { > > + warned = 1; > > + pr_warn("Overriding per-console loglevel from sysrq\n"); It just came to my mind. We could use pr_warn_once() and get rid of the @warned variable. It is slightly less optimal. But this is a slow path and the code would be easier. > > + } > > + WRITE_ONCE(con->level, -1); > > + } > > + console_srcu_read_unlock(cookie); > > } > > + > Best Regards, Petr