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charset="utf-8" The /sys/devices/system/cpu/nohz_full file is a read-only attribute that reports the CPUs configured for tickless operation (CONFIG_NO_HZ_FULL=3Dy). The current definition uses the generic DEVICE_ATTR macro, which unnecessarily requires specifying the file mode (0444) and a NULL store operation pointer. This patch converts the definition to use the dedicated DEVICE_ATTR_RO macro. This correctly expresses the read-only nature of the attribute, removes the redundant mode field, and simplifies the code. As a related cleanup, rename the show function from print_cpus_nohz_full() to the standard nohz_full_show() for consistency with common sysfs attribute naming conventions. Signed-off-by: Aaron Tomlin --- drivers/base/cpu.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index fa0a2eef93ac..c792ec66462d 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -301,12 +301,13 @@ static ssize_t print_cpus_isolated(struct device *dev, static DEVICE_ATTR(isolated, 0444, print_cpus_isolated, NULL); =20 #ifdef CONFIG_NO_HZ_FULL -static ssize_t print_cpus_nohz_full(struct device *dev, - struct device_attribute *attr, char *buf) +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)); } -static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL); +static DEVICE_ATTR_RO(nohz_full); #endif =20 #ifdef CONFIG_CRASH_HOTPLUG --=20 2.49.0 From nobody Wed Dec 17 19:17:02 2025 Received: from LO3P265CU004.outbound.protection.outlook.com (mail-uksouthazon11020105.outbound.protection.outlook.com [52.101.196.105]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B26D83AC1C for ; 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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