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Mon, 1 Oct 2018 00:39:36 +0000 Received: from CY4PR21MB0776.namprd21.prod.outlook.com ([fe80::54e2:88e0:b622:b36]) by CY4PR21MB0776.namprd21.prod.outlook.com ([fe80::54e2:88e0:b622:b36%5]) with mapi id 15.20.1228.006; Mon, 1 Oct 2018 00:39:36 +0000 From: Sasha Levin To: "stable@vger.kernel.org" , "linux-kernel@vger.kernel.org" CC: vkuznets , Boris Ostrovsky , Sasha Levin Subject: [PATCH AUTOSEL 4.18 62/65] xen/manage: don't complain about an empty value in control/sysrq node Thread-Topic: [PATCH AUTOSEL 4.18 62/65] xen/manage: don't complain about an empty value in control/sysrq node Thread-Index: AQHUWR8ZQQZeM84ZYk+O9P7xsJBXvw== Date: Mon, 1 Oct 2018 00:38:41 +0000 Message-ID: <20181001003754.146961-62-alexander.levin@microsoft.com> References: <20181001003754.146961-1-alexander.levin@microsoft.com> In-Reply-To: <20181001003754.146961-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;CY4PR21MB0696;6:qoHKXAQ32xFDHtItHCW+VCirIyJCZxw2FlOLspra7j9MzHSlJanJOzd5MRsg1ujc2vx7LtHgN1+v7pwW2DDWyI6Wy1mbHHlZDTAlFSNkagoWPFDqVL+tKiV+RA29GrCA9h9tXGck9zccsOkTpAwqYBIwH8DTwkoenwvB93YxqIKvvEOSZCX7t5Tb3J7IYXRiwiiiuHEXkBYzvC4dqHWvd4o4OJrsHKasUtZlAZxybCPhxYoSQAOaTDNVJIO83LXF+bj49vmHS0vmLl2vQ2Icy+Aoz4DFF2gKSQGPKC7NtEaOATVXUNth+168d+PUcQP0vaCVergA9EXG82YmjEGv//QWZF06d5Ulbn7HDP7XvBlFmJkpYGtEA7S01seBipgITg9LC0vjsT7YbxypQNl3b/T1INQr9ZjueANZ2Yi8UOwb9pd1s6uzeSiuN6UTWimgEmZYZpJXXuSbPV+nWHejzQ==;5:q7/Rgcau7F7WtqMsj1WFYsWO7JGqnlA/QgY8QmADkxX0lgZW8mg8Yk6a+GL4K0UkmSH+JAH66/HMZMhiDDLqDvI2wk8r/o+wYqQ8vHcmJB1Wm42AhzvihdjNgAR1+nhg4W5FLfX9fG8yNlzzCUa2YhRXBVtAALxg/A30KyeeFxg=;7:zG/YUUN28EBHGbz32QjVVK6v+UZMrc+Nu3hpibyB7NNXmh1hCSch6VJ/8dsqzxutQMO7XLvelZ4f2xLHUZ2QEWCz8C0/m3QD5qC8LCzOfVixOvj69Bp10NruvIwxVQdsI0tXcCCKm3hzt4/3w4iDg5Zwgiq5g+T1IXXUaBkRJS/rjnj6L7CcvUWOMr9T8MiYHDA+xHauaJigSzZli1GNHhZXs1tDCvJyxBHw1kB0dNloMkzPtSxbcOPcd3fDx3Og x-ms-office365-filtering-correlation-id: 20c68a10-e02d-4117-45d0-08d627365d5b x-ms-office365-filtering-ht: Tenant x-microsoft-antispam: BCL:0;PCL:0;RULEID:(7020095)(4652040)(8989299)(4534165)(4627221)(201703031133081)(201702281549075)(8990200)(5600074)(711020)(4618075)(2017052603328)(7193020);SRVR:CY4PR21MB0696; 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received-spf: None (protection.outlook.com: microsoft.com does not designate permitted sender hosts) x-microsoft-antispam-message-info: 489aov1HjcykKrWZb6pgUu4EcdeQybWqm8mF5GX3oTduIOR08N3UILAkWAXzio2yB4BVrXzAsK6Tpn/31A+mz/wWRBTP0RahvW9vJwu60/e2nT22E+gRWPPpijTvssYLtzR4SHZuBenkTlMnXIorlYEi5hK0o3QWW9zojZqO1Ma0tXX9IT2KIvmwNHQ7jpsrDP0YgCIVsZqTaAkrjTBRdOvKirwxfHin+zyj+mxNUFd2/ISdB/C3lnL4ihELNozYMDcvSHHlQ3UhliEsTsRjpvJrVZE57B+6YCBlQnO1uVoz1FJS62PoKTeeHszdyGEypObQfttq7t5B8Uvm7KrxQov5m/sgyJ9lP8f0z0ikZ9g= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: 20c68a10-e02d-4117-45d0-08d627365d5b X-MS-Exchange-CrossTenant-originalarrivaltime: 01 Oct 2018 00:38:41.4605 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY4PR21MB0696 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Vitaly Kuznetsov [ Upstream commit 87dffe86d406bee8782cac2db035acb9a28620a7 ] When guest receives a sysrq request from the host it acknowledges it by writing '\0' to control/sysrq xenstore node. This, however, make xenstore watch fire again but xenbus_scanf() fails to parse empty value with "%c" format string: sysrq: SysRq : Emergency Sync Emergency Sync complete xen:manage: Error -34 reading sysrq code in control/sysrq Ignore -ERANGE the same way we already ignore -ENOENT, empty value in control/sysrq is totally legal. Signed-off-by: Vitaly Kuznetsov Reviewed-by: Wei Liu Signed-off-by: Boris Ostrovsky Signed-off-by: Sasha Levin --- drivers/xen/manage.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c index c93d8ef8df34..5bb01a62f214 100644 --- a/drivers/xen/manage.c +++ b/drivers/xen/manage.c @@ -280,9 +280,11 @@ static void sysrq_handler(struct xenbus_watch *watch, = const char *path, /* * The Xenstore watch fires directly after registering it and * after a suspend/resume cycle. So ENOENT is no error but - * might happen in those cases. + * might happen in those cases. ERANGE is observed when we get + * an empty value (''), this happens when we acknowledge the + * request by writing '\0' below. */ - if (err !=3D -ENOENT) + if (err !=3D -ENOENT && err !=3D -ERANGE) pr_err("Error %d reading sysrq code in control/sysrq\n", err); xenbus_transaction_end(xbt, 1); --=20 2.17.1