From: Clark Williams Date: Sat, 30 Jul 2011 21:55:53 -0500 Subject: [PATCH 214/353] sysfs: Add /sys/kernel/realtime entry Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=63cdf57144587bc178a94170e17c65477542af67 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 --- kernel/ksysfs.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c index 46ba853656f6..9a23632b6294 100644 --- a/kernel/ksysfs.c +++ b/kernel/ksysfs.c @@ -140,6 +140,15 @@ KERNEL_ATTR_RO(vmcoreinfo); #endif /* CONFIG_CRASH_CORE */ +#if defined(CONFIG_PREEMPT_RT_FULL) +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) @@ -230,6 +239,9 @@ static struct attribute * kernel_attrs[] = { #ifndef CONFIG_TINY_RCU &rcu_expedited_attr.attr, &rcu_normal_attr.attr, +#endif +#ifdef CONFIG_PREEMPT_RT_FULL + &realtime_attr.attr, #endif NULL };