From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-4061326-1516722767-2-16532482878382466341 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.25, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='US', FromHeader='uk', MailFrom='org' X-Spam-charsets: plain='US-ASCII' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: linux-serial-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1516722767; b=kYib5gA0h/R9sxVm5ZKW/I8BAVwVgatwGsc2XIRs9QAlz4z qcrcOwErwWUSh0VDwaox5TU5B0HL+1hbr5EI9SigJ32xrOsXdux8W9f+uMf6uZKg 9fSpeGJy5CRb2UPtHPtZXl9QqcCi1CmXBiMAh8g6sLHZYGstoAx/ej2igUbuLSsD lDrRIGdNXX5YmB0LVV6s5dWKs4qFqUkLO7Zyli1eD4xUwqdvdq5yiLheKWoDRuBx Sq/HEUeE7XgOJqw4sB2nf8/B8j89qnhk8HL5yv7T4PuQUcOsN/okJ4YixMpMrEkH 1hStfl7NrxXqTKfitJhytxpiFFw1TbFgjYbXjfw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=date:from:to:cc:subject:message-id :in-reply-to:references:mime-version:content-type :content-transfer-encoding:sender:list-id; s=arctest; t= 1516722767; bh=5niuoEMrx4Q16SdFJN8/Y9knHURvd87O2/M3Gq2s2dQ=; b=o 9lgg1hnvPAffTmuzdFTdIzPpDF0RdreRAZXYbzQ5EFaOjOQ7HtJMQYgqXprBqkYv ccLXt65fwks1e3UsvcYigA6aKRDT74QABEz3SGEWNuEZh8oUUhvRAnBRXZuXys7M arayIlGIKrgeYtHp3NBZdUoVIJwIt6UQLVq62fbQTzovvpEIKR9tkieAClgy+KWM YVfkQfapXENydsO0s3IeHzCHOHMvvZwcDY0WMrdnhAjQLo2Rb6yW+uTpRIe6rTs3 nR/4hVXd49LqS9cf09l9CnGyJkl2HvLoHFlwFcoM9hxToUm0bRqgVas4uZWIoYbj UANayhvwz37CY7ozvIc3g== ARC-Authentication-Results: i=1; mx6.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=lxorguk.ukuu.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-serial-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=lxorguk.ukuu.org.uk header.result=pass header_org.domain=ukuu.org.uk header_org.result=pass header_is_org_domain=no Authentication-Results: mx6.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=lxorguk.ukuu.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-serial-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=lxorguk.ukuu.org.uk header.result=pass header_org.domain=ukuu.org.uk header_org.result=pass header_is_org_domain=no Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751258AbeAWPwo (ORCPT ); Tue, 23 Jan 2018 10:52:44 -0500 Received: from www.llwyncelyn.cymru ([82.70.14.225]:57444 "EHLO fuzix.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751255AbeAWPwn (ORCPT ); Tue, 23 Jan 2018 10:52:43 -0500 Date: Tue, 23 Jan 2018 15:52:29 +0000 From: Alan Cox To: Shankara Pailoor Cc: Greg KH , jslaby@suse.com, LKML , syzkaller , linux-serial@vger.kernel.org Subject: Re: RCU stall in 8250 serial driver Linux 4.15-rc1 Message-ID: <20180123155229.2035e674@alans-desktop> In-Reply-To: References: <20180117170520.GA12606@kroah.com> Organization: Intel Corporation X-Mailer: Claws Mail 3.15.1-dirty (GTK+ 2.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-serial-owner@vger.kernel.org X-Mailing-List: linux-serial@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Wed, 17 Jan 2018 09:24:32 -0800 Shankara Pailoor wrote: > Hi Greg, > > Sorry for that. Here is the stack trace. C Program below > serial_in drivers/tty/serial/8250/8250.h:111 [inline] > wait_for_xmitr+0x8a/0x1d0 drivers/tty/serial/8250/8250_port.c:2033 > serial8250_console_putchar+0x19/0x50 drivers/tty/serial/8250/8250_port.c:3170 > uart_console_write+0x98/0xc0 drivers/tty/serial/serial_core.c:1858 The console is spinning in polled mode trying to write data to the console port, which it seems has gotten a bit stuck. Could be the hypervisor hits some kind of buffering limit, could be hypervisor interface broke. Either way the console interface is supposed to stall the machine to ensure the bytes always get out and if your serial port jams or gets massively behind then this will happen. Alan