From patchwork Mon Oct 19 10:06:31 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Gleixner X-Patchwork-Id: 11844015 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 93F2014B4 for ; Mon, 19 Oct 2020 10:19:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6DAF422363 for ; Mon, 19 Oct 2020 10:19:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="1y/pZhJx"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="EpF5wNFf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726527AbgJSKT0 (ORCPT ); Mon, 19 Oct 2020 06:19:26 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:58718 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727617AbgJSKSH (ORCPT ); Mon, 19 Oct 2020 06:18:07 -0400 Message-Id: <20201019101109.753597069@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1603102684; 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: references:references; bh=j+vN9MgqREoIPGzBU7B1IaC3gna3kE7EN539Nh0ClUU=; b=1y/pZhJxP37rV0rJYULPo5TQOwi6HefvUHI6uFl3VyOzD/l9uItuaHM5eXK388fs3OFUXW hSALKKpI69M2O4c+bSYlejPpYC6pICFSdC9DdfpTR/WtEqHVmyWlGZ+GOOBhf/+1M2nn29 K9Ga9SNsF0iu3YuoJ8ieIZOcFDNbs7crX5QWXNnnL8OkI9EqFafV4MUDr09pVBNkgyaTYq lMqXxV5G1EGaMcFJEjIZDV+CwcdjhGM+KvQa1oyHADBQYrm2SkHPH1DvvUHpNr+AqEDlbz kkjpapE1LHCy0rvx+yyCA+R3G4M6QCC3WbG4xLKPNBSZX+OXtuvTiN7HxJfL8Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1603102684; 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: references:references; bh=j+vN9MgqREoIPGzBU7B1IaC3gna3kE7EN539Nh0ClUU=; b=EpF5wNFfU2q3Hnqoz5MF6cC6OkRPZavOxiE1H65l6nfC8pvMxSVoO1CNGgrw1X764TZuoK DwpXwGIMneJN/sAQ== Date: Mon, 19 Oct 2020 12:06:31 +0200 From: Thomas Gleixner To: LKML Cc: Peter Zijlstra , "Ahmed S. Darwish" , Sebastian Andrzej Siewior , Johan Hovold , Greg Kroah-Hartman , linux-usb@vger.kernel.org, Thomas Winischhofer , Mathias Nyman , Valentina Manea , Shuah Khan , Alan Stern , linux-omap@vger.kernel.org, Kukjin Kim , Krzysztof Kozlowski , linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, Felipe Balbi , Duncan Sands Subject: [patch V2 02/13] USB: serial: keyspan_pda: Replace in_interrupt() usage References: <20201019100629.419020859@linutronix.de> MIME-Version: 1.0 Content-transfer-encoding: 8-bit Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org keyspan_pda_write() uses in_interrupt() to check whether it is safe to invoke functions which might sleep. The usage of in_interrupt() in drivers is phased out and Linus clearly requested that code which changes behaviour depending on context should either be seperated or the context be conveyed in an argument passed by the caller, which usually knows the context. Aside of that it does not cover all contexts which cannot sleep, e.g. preempt disabled regions which cannot be reliably detected on all kernel configurations. With the current printk() implementation console->write() can be invoked from almost any context. The upcoming rework of the console core will provide thread context for console drivers which require to sleep. For now, restrict the room query which can sleep to tty writes which happen from preemptible task context. The usability for dmesg output is limited anyway because it's almost guaranteed to drop the 'LF' which is submitted after the dmesg line because the device supports only one transfer on flight. Same for any printk() which is coming in before the previous transfer has been done. This new restriction does not make it worse than before, but it makes the condition correct under all circumstances. Signed-off-by: Ahmed S. Darwish Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Cc: Johan Hovold Cc: Greg Kroah-Hartman Cc: linux-usb@vger.kernel.org --- drivers/usb/serial/keyspan_pda.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/drivers/usb/serial/keyspan_pda.c +++ b/drivers/usb/serial/keyspan_pda.c @@ -477,10 +477,12 @@ static int keyspan_pda_write(struct tty_ count = (count > port->bulk_out_size) ? port->bulk_out_size : count; - /* Check if we might overrun the Tx buffer. If so, ask the - device how much room it really has. This is done only on - scheduler time, since usb_control_msg() sleeps. */ - if (count > priv->tx_room && !in_interrupt()) { + /* + * Check if we might overrun the Tx buffer. If so, ask the device + * how much room it really has. This can only be invoked for tty + * usage because the console write can't sleep. + */ + if (count > priv->tx_room && tty) { u8 *room; room = kmalloc(1, GFP_KERNEL);