From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 36C4D1C57AA; Wed, 18 Sep 2024 15:19:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726672749; cv=none; b=bcYwKZg8j64KgCBvc2hgJzpZowsTlAgZvchHyvCHyb7d0aFARIhtGPPJOi0tYGkkTh+tC8FpdjWOkUoThYc6su1/JugOHo2G2ESYsVk/QI+218VlHx4/7zgDBR4jIClP6E++YDjWtahF8vh3WfxSpuF/Jw+4FdYO5me/v4/POJ8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726672749; c=relaxed/simple; bh=ZMAZ7vKEqHUBAukSpcLjPwhLOZQg2LUVZxwDz6JRLKc=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=QJM8mJi5xGPC4bvFTezjTF74goa1QOVPlNoImL9+fYNXjkM7S63VOVeihXCJTqNgnQhe4In6njs2rZAz/dTf4vvyK4hCNvCg37+u5pTrIiGWtHHLPvkfWhwMs6G1kWEH6K5bJWEyXGdlmJVUlbGwUeHFTh3avOL61c/nSOxitr8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=22wUL/kq; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=bbwtiS3s; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="22wUL/kq"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="bbwtiS3s" From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1726672746; 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: in-reply-to:in-reply-to:references:references; bh=ZMAZ7vKEqHUBAukSpcLjPwhLOZQg2LUVZxwDz6JRLKc=; b=22wUL/kqdZo2yHNCCPpQHmAtEpfdddS2eBGOMJLarAa48yRU5gW/wdO/38cPG0R9SPSYQ8 K9hGRT54FuIwCElY8q2q6krJk+aJ3K5bXzTcAt5pEiNQrncGWHaWCRLhhjriDcx9XENt5b DGzAFPUQoLpH+FZGl9BbFtYjO5l/vaka6grgIpK+sx+3Rqs3zLwA0Eq/Y6jSs1ds6dZFnY Mlg5E39fPyp5PSiBmRpLClVo2XUleDgwk2s6JwcrrkOjE2352tyTOgd9P7NBshor4Q07tp ZHZA8utQBxTPwjLn95t0oEMMav0GWlodG96yStJcT8mNVTvkMTEnl7jWwXzYxQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1726672746; 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: in-reply-to:in-reply-to:references:references; bh=ZMAZ7vKEqHUBAukSpcLjPwhLOZQg2LUVZxwDz6JRLKc=; b=bbwtiS3sBwfO/7jPUTsZdSak29bPGHBhiz1cAo+r2rQeX2OP1q65g4AXFvSzrE26Wi+xEl 9gWAPjPghxsHVdAA== To: Petr Mladek Cc: Greg Kroah-Hartman , Jiri Slaby , Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , Esben Haabendal , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Andy Shevchenko , Tony Lindgren , Ilpo =?utf-8?Q?J=C3=A4rvinen?= , Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= , Arnd Bergmann , Florian Fainelli , Serge Semin , Wolfram Sang , Lino Sanfilippo Subject: Re: [PATCH next v2 3/4] serial: 8250: Switch to nbcon console In-Reply-To: References: <20240913140538.221708-1-john.ogness@linutronix.de> <20240913140538.221708-4-john.ogness@linutronix.de> Date: Wed, 18 Sep 2024 17:25:05 +0206 Message-ID: <84ed5hrnva.fsf@jogness.linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On 2024-09-18, Petr Mladek wrote: > It would be fair to mention that it does not longer support fifo in > the 8250 driver. It basically reverted the commit 8f3631f0f6eb42e5 > ("serial/8250: Use fifo in 8250 console driver"). Agreed. > It is not usable in write_thread() because it would not allow > a safe takeover between emitting particular characters. If write_thread could exit_unsafe()/enter_unsafe() while busy-waiting, then emergency/panic could still take over at any time. Even if it means that atomic_write() would need to first wait for the FIFO to drain (which it will). The important thing is that emergency/panic is able to take over. I dropped the optimization to keep things simple for now, but I agree with Andy that it would be unfortunate. I will take a look at what such an implementation could look like. John