From f10c23fa159c5481dfe0025e619dc5ef844f6ce1 Mon Sep 17 00:00:00 2001 From: Aaron Tomlin Date: Fri, 10 Oct 2025 21:18:30 -0400 Subject: tick/nohz: avoid showing '(null)' if nohz_full= not set MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In the context of CONFIG_NO_HZ_FULL=y, tick_nohz_full_mask (of type cpumask_var_t) is initialised to 0. Memory is only allocated to the cpumask data structure, in tick_nohz_full_setup(), when Linux kernel boot-time parameter "nohz_full=" is correctly specified (see housekeeping_setup()). If "nohz_full=" is not set and an attempt is made to read /sys/devices/system/cpu/nohz_full, '(null)' can be displayed: ❯ 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 Link: https://patch.msgid.link/20251011011830.6670-3-atomlin@atomlin.com Signed-off-by: Greg Kroah-Hartman --- drivers/base/cpu.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'drivers/base/cpu.c') 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 -- cgit v1.2.3