From dcf884dcf755fc4740836e965c6ccf4c2859beb3 Mon Sep 17 00:00:00 2001 From: Clark Williams Date: Sat, 30 Jul 2011 21:55:53 -0500 Subject: [PATCH 154/166] sysfs: Add /sys/kernel/realtime entry Add a /sys/kernel entry to indicate that the kernel is a realtime kernel. Clark says that he needs this for udev rules, udev needs to evaluate if its a PREEMPT_RT kernel a few thousand times and parsing uname output is too slow or so. Are there better solutions? Should it exist and return 0 on !-rt? Signed-off-by: Clark Williams Signed-off-by: Peter Zijlstra Signed-off-by: Thomas Gleixner --- kernel/ksysfs.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) Index: linux-5.15.32-rt39/kernel/ksysfs.c =================================================================== --- linux-5.15.32-rt39.orig/kernel/ksysfs.c +++ linux-5.15.32-rt39/kernel/ksysfs.c @@ -138,6 +138,15 @@ KERNEL_ATTR_RO(vmcoreinfo); #endif /* CONFIG_CRASH_CORE */ +#if defined(CONFIG_PREEMPT_RT) +static ssize_t realtime_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%d\n", 1); +} +KERNEL_ATTR_RO(realtime); +#endif + /* whether file capabilities are enabled */ static ssize_t fscaps_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) @@ -229,6 +238,9 @@ static struct attribute * kernel_attrs[] &rcu_expedited_attr.attr, &rcu_normal_attr.attr, #endif +#ifdef CONFIG_PREEMPT_RT + &realtime_attr.attr, +#endif NULL };