Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754079AbbG2IWU (ORCPT ); Wed, 29 Jul 2015 04:22:20 -0400 Received: from TYO201.gate.nec.co.jp ([210.143.35.51]:52338 "EHLO tyo201.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753085AbbG2IWR convert rfc822-to-8bit (ORCPT ); Wed, 29 Jul 2015 04:22:17 -0400 From: Taichi Kageyama To: "gregkh@linuxfoundation.org" CC: "linux-serial@vger.kernel.org" , "jslaby@suse.cz" , "linux-kernel@vger.kernel.org" , "prarit@redhat.com" , Naoya Horiguchi Subject: Re: [PATCH 1/2] serial: 8250: Fix autoconfig_irq() to avoid race conditions Thread-Topic: [PATCH 1/2] serial: 8250: Fix autoconfig_irq() to avoid race conditions Thread-Index: AQHQn3YPfR1JLIP5kUuZc3LH0ejwmp3pWP4AgAh+LgA= Date: Wed, 29 Jul 2015 08:13:44 +0000 Message-ID: <55B88B38.4070703@cp.jp.nec.com> References: <55717224.9060104@cp.jp.nec.com> <55717294.8020905@cp.jp.nec.com> <20150723223202.GA23915@kroah.com> In-Reply-To: <20150723223202.GA23915@kroah.com> Accept-Language: en-US, ja-JP Content-Language: ja-JP X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.34.108.73] Content-Type: text/plain; charset="iso-2022-jp" Content-ID: <81439D3C2E113947ACDD9353532602CB@gisp.nec.co.jp> Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2227 Lines: 49 On 2015/07/24 7:32, gregkh@linuxfoundation.org wrote: > On Fri, Jun 05, 2015 at 09:57:40AM +0000, Taichi Kageyama wrote: >> The following race conditions can happen if a serial is used as console. >> Case1. CPU_B handles an interrupt from a serial >> autoconfig_irq() fails whether the interrupt is raised or not >> if CPU_B is disabled to handle interrupts for longer than it expects. >> Case2. CPU_B clears UART_IER just after CPU_A sets UART_IER >> A serial may not make an interrupt. >> autoconfig_irq() can fail if the interrupt is not raised. >> Case3. CPU_A sets UART_IER just after CPU_B clears UART_IER >> This is an unexpected behavior for uart_console_write(). >> >> CPU_A [autoconfig_irq] CPU_B [serial8250_console_write] >> ----------------------------------------------------------------- >> probe_irq_on() spin_lock_irqsave(&port->lock,) >> serial_outp(,UART_IER,0x0f) serial_out(,UART_IER,0) >> udelay(20); uart_console_write() >> probe_irq_off() >> spin_unlock_irqrestore(&port->lock,) >> ----------------------------------------------------------------- >> >> If autoconfig_irq() fails, the console doesn't work in interrupt mode, >> the mode cannot be changed anymore, and "input overrun" >> (which can make operation mistakes) happens easily. >> This problem happens with high rate every boot once it occurs >> because the boot sequence is always almost same. >> >> Signed-off-by: Taichi Kageyama >> Cc: Naoya Horiguchi >> Reviewed-by: Peter Hurley >> --- >> drivers/tty/serial/8250/8250_core.c | 6 ++++++ >> 1 files changed, 6 insertions(+), 0 deletions(-) > > Does not apply to 4.2-rc3 :( > Sorry for the trouble and late reply. It's my fault. It was encoded as base64 by Exchange. I sent new patch set including this patch. I updated commit log. Regards, Taichi-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/