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Sat, 11 Oct 2025 01:18:45 +0000 From: Aaron Tomlin To: gregkh@linuxfoundation.org, nathan@kernel.org, rafael@kernel.org, dakr@kernel.org Cc: riel@surriel.com, frederic@kernel.org, atomlin@atomlin.com, linux-kernel@vger.kernel.org Subject: [PATCH v3 2/2] tick/nohz: avoid showing '(null)' if nohz_full= not set Date: Fri, 10 Oct 2025 21:18:30 -0400 Message-ID: <20251011011830.6670-3-atomlin@atomlin.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20251011011830.6670-1-atomlin@atomlin.com> References: <20251011011830.6670-1-atomlin@atomlin.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: BL0PR02CA0056.namprd02.prod.outlook.com (2603:10b6:207:3d::33) To CWLP123MB3523.GBRP123.PROD.OUTLOOK.COM (2603:10a6:400:70::10) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CWLP123MB3523:EE_|LO0P123MB7766:EE_ X-MS-Office365-Filtering-Correlation-Id: 16616748-81de-4ad3-188c-08de08641f7c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014; 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Memory is only allocated to the cpumask data structure, in tick_nohz_full_setup(), when Linux kernel boot-time parameter "nohz_full=3D" is correctly specified (see housekeeping_setup()). If "nohz_full=3D" is not set and an attempt is made to read /sys/devices/system/cpu/nohz_full, '(null)' can be displayed: =E2=9D=AF cat /sys/devices/system/cpu/nohz_full (null) This patch changes the output to print a newline (or 0x0A) instead of '(null)', making it consistent with print_cpus_isolated() behaviour. Signed-off-by: Aaron Tomlin --- drivers/base/cpu.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index c792ec66462d..e3cb47eae982 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -305,7 +305,10 @@ static ssize_t nohz_full_show(struct device *dev, struct device_attribute *attr, char *buf) { - return sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(tick_nohz_full_mask)); + if (cpumask_available(tick_nohz_full_mask)) + return sysfs_emit(buf, "%*pbl\n", + cpumask_pr_args(tick_nohz_full_mask)); + return sysfs_emit(buf, "\n"); } static DEVICE_ATTR_RO(nohz_full); #endif --=20 2.49.0