From: Aaron Tomlin Date: Sat, 11 Oct 2025 01:18:30 +0000 (-0400) Subject: tick/nohz: avoid showing '(null)' if nohz_full= not set X-Git-Tag: v6.19-rc1~90^2~8 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f10c23fa159c5481dfe0025e619dc5ef844f6ce1;p=thirdparty%2Fkernel%2Flinux.git tick/nohz: avoid showing '(null)' if nohz_full= not set 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 --- diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index c792ec66462d8..e3cb47eae9822 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