From mboxrd@z Thu Jan 1 00:00:00 1970 From: Taichi Kageyama Subject: [PATCH 0/2] serial: 8250: Workaround to avoid irq=0 for console Date: Fri, 5 Jun 2015 09:55:48 +0000 Message-ID: <55717224.9060104@cp.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Language: ja-JP Content-ID: Sender: linux-kernel-owner@vger.kernel.org To: "gregkh@linuxfoundation.org" Cc: "linux-serial@vger.kernel.org" , "jslaby@suse.cz" , "linux-kernel@vger.kernel.org" , "prarit@redhat.com" , Naoya Horiguchi List-Id: linux-serial@vger.kernel.org VGhpcyBwYXRjaCBzZXQgcHJvdmlkZXMgYSB3b3JrYXJvdW5kIHRvIGF2b2lkIHRoZSBmb2xsb3dp bmcgcHJvYmxlbS4NCkl0J3MgYmFzZWQgb24gTGludXggNC4xLXJjMyBtYWluc3RyZWFtIGtlcm5l bC4NCkkndmUgdGVzdGVkIHRoaXMgcGF0Y2ggc2V0IG9uIHg4Ni02NCBtYWNoaW5lIGFuZCBLVk0u DQoNClByb2JsZW0NCi0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tDQpUaGVyZSdyZSBjYXNlcyB3 aGVyZSBhdXRvY29uZmlnX2lycSgpIGZhaWxzIGR1cmluZyBib290Lg0KSW4gdGhlc2UgY2FzZXMs IHRoZSBjb25zb2xlIGRvZXNuJ3Qgd29yayBpbiBpbnRlcnJ1cHQgbW9kZSwNCnRoZSBtb2RlIGNh bm5vdCBiZSBjaGFuZ2VkIGFueW1vcmUsIGFuZCAiaW5wdXQgb3ZlcnJ1biINCih3aGljaCBjYW4g bWFrZSBvcGVyYXRpb24gbWlzdGFrZXMpIGhhcHBlbnMgZWFzaWx5Lg0KVGhpcyBwcm9ibGVtIGhh cHBlbnMgd2l0aCBoaWdoIHJhdGUgZXZlcnkgYm9vdCBvbmNlIGl0IG9jY3Vycw0KYmVjYXVzZSB0 aGUgYm9vdCBzZXF1ZW5jZSBpcyBhbHdheXMgYWxtb3N0IHNhbWUuDQpJIHNhdyB0aGUgb3JpZ2lu YWwgcHJvYmxlbSBvbiBSSEVMNi42Lg0KDQpGaXgNCi0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0t DQpzZXJpYWw6IDgyNTA6IEZpeCBhdXRvY29uZmlnX2lycSgpIHRvIGF2b2lkIHJhY2UgY29uZGl0 aW9ucw0KICBGaXggb25lIG9mIGF1dG9jb25maWdfaXJxKCkgZmFpbHVyZSBjYXNlLg0Kc2VyaWFs OiA4MjUwOiBBbGxvdyB0byBza2lwIGF1dG9jb25maWdfaXJxKCkgZm9yIGEgY29uc29sZQ0KICBQ cm92aWRlIGEgd29ya2Fyb3VuZCB0byBhdm9pZCBvdGhlciBhdXRvY29uZmlnX2lycSgpIGZhaWx1 cmUgY2FzZXMuDQoNCkNvbmRpdGlvbnMgb2YgUmVwcm9kdWN0aW9uDQotLS0tLS0tLS0tLS0tLS0t LS0tLS0tLS0tLQ0KLSBCdWlsZCB3aXRoIENPTkZJR19TRVJJQUxfODI1MF9ERVRFQ1RfSVJRLg0K LSBOZWVkIG5vbi1QblAgY29uc29sZSBzZXJpYWwgb3IgUG5QIGNvbnNvbGUgd2l0aCBubyBDT05G SUdfU0VSSUFMXzgyNTBfUE5QDQotIEtpY2sgcHJpbnRrKCkgcmVwZWF0ZWRseSBvbiB0aGUgQ1BV IHdoaWNoIGNhbiBoYW5kbGUgYW4gaW50ZXJydXB0DQogICBmcm9tIGEgY29uc29sZSBzZXJpYWwg ZHVyaW5nIGF1dG9jb25maWdfaXJxKCkuIFRoZSBDUFUgaXMgYmFzaWNhbGx5IGNwdTAuDQotIERp c2FibGUgdGhlIGludGVycnVwdCBvZiB0aGUgQ1BVIGZvciBsb25nZXIgZHVyaW5nIGF1dG9jb25m aWdfaXJxKCkuDQoNCk5vdGUNCi0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tDQpJZGVhbGx5LCBJ IHRoaW5rIGF1dG9jb25maWdfaXJxKCkgc2hvdWxkIGJlIGZpeGVkIGNvbXBsZXRlbHksDQpidXQg aXQncyBoYXJkIGZyb20gdGhlIGZvbGxvd2luZyBwb2ludHMNCmFzIGxvbmcgYXMgYXV0b19pcnEg YWxnb3JpdGhtIGlzIHVzZWQuDQogIC0gSG93IGxvbmcgaXQgc2hvdWxkIHdhaXQgZm9yIGFuIGlu dGVycnJ1cHQNCiAgLSBIb3cgdG8gYXNzdXJlIHRoZSBpbnRlcnJ1cHQgb2YgdGhlIENQVSBlbmFi bGVkIGR1cmluZyBhdXRvX2lycQ0KICAtIEhvdyB0byBrbm93IHdoaWNoIENQVSBjYW4gaGFuZGxl IGFuIGludGVycnVwdCBmcm9tIGEgc2VyaWFsLg0KDQpEbyB5b3UgaGF2ZSBhbnkgb3RoZXIgaWRl YT8NCkluIG15IG9waW5pb24sIHByb3ZpZGluZyBhIHdvcmthcm91bmQgaXMgYmV0dGVyIHRoYW4N CmFwcGx5aW5nIGJpZyBjaGFuZ2VzIHRvIHRoZSBvbGQgZnVuY3Rpb24gZm9yIGxlZ2FjeSBkZXZp Y2VzLg0KDQpUYWljaGkgS2FnZXlhbWEgKDIpOg0KICAgc2VyaWFsOiA4MjUwOiBGaXggYXV0b2Nv bmZpZ19pcnEoKSB0byBhdm9pZCByYWNlIGNvbmRpdGlvbnMNCiAgIHNlcmlhbDogODI1MDogQWxs b3cgdG8gc2tpcCBhdXRvY29uZmlnX2lycSgpIGZvciBhIGNvbnNvbGUNCg0KICBkcml2ZXJzL3R0 eS9zZXJpYWwvODI1MC84MjUwX2NvcmUuYyB8ICAgMjMgKysrKysrKysrKysrKysrKysrKysrKysN CiAgMSBmaWxlcyBjaGFuZ2VkLCAyMyBpbnNlcnRpb25zKCspLCAwIGRlbGV0aW9ucygtKQ0K From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754498AbbFEKJm (ORCPT ); Fri, 5 Jun 2015 06:09:42 -0400 Received: from TYO200.gate.nec.co.jp ([210.143.35.50]:60597 "EHLO tyo200.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751149AbbFEKJi (ORCPT ); Fri, 5 Jun 2015 06:09:38 -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: [PATCH 0/2] serial: 8250: Workaround to avoid irq=0 for console Thread-Topic: [PATCH 0/2] serial: 8250: Workaround to avoid irq=0 for console Thread-Index: AQHQn3XM4Pt7XBRbREauQ4fcrjoxhw== Date: Fri, 5 Jun 2015 09:55:48 +0000 Message-ID: <55717224.9060104@cp.jp.nec.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="utf-8" Content-ID: MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by nfs id t55A9mUa009980 This patch set provides a workaround to avoid the following problem. It's based on Linux 4.1-rc3 mainstream kernel. I've tested this patch set on x86-64 machine and KVM. Problem -------------------------- There're cases where autoconfig_irq() fails during boot. In these cases, 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. I saw the original problem on RHEL6.6. Fix -------------------------- serial: 8250: Fix autoconfig_irq() to avoid race conditions Fix one of autoconfig_irq() failure case. serial: 8250: Allow to skip autoconfig_irq() for a console Provide a workaround to avoid other autoconfig_irq() failure cases. Conditions of Reproduction -------------------------- - Build with CONFIG_SERIAL_8250_DETECT_IRQ. - Need non-PnP console serial or PnP console with no CONFIG_SERIAL_8250_PNP - Kick printk() repeatedly on the CPU which can handle an interrupt from a console serial during autoconfig_irq(). The CPU is basically cpu0. - Disable the interrupt of the CPU for longer during autoconfig_irq(). Note -------------------------- Ideally, I think autoconfig_irq() should be fixed completely, but it's hard from the following points as long as auto_irq algorithm is used. - How long it should wait for an interrrupt - How to assure the interrupt of the CPU enabled during auto_irq - How to know which CPU can handle an interrupt from a serial. Do you have any other idea? In my opinion, providing a workaround is better than applying big changes to the old function for legacy devices. Taichi Kageyama (2): serial: 8250: Fix autoconfig_irq() to avoid race conditions serial: 8250: Allow to skip autoconfig_irq() for a console drivers/tty/serial/8250/8250_core.c | 23 +++++++++++++++++++++++ 1 files changed, 23 insertions(+), 0 deletions(-) {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I