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Subject: sysfs: Add /sys/kernel/realtime entry
From: Clark Williams <williams@redhat.com>
Date: Sat Jul 30 21:55:53 2011 -0500
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.0/older/patches-5.0.7-rt5.tar.xz
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 <williams@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
kernel/ksysfs.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
--- 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)
@@ -231,6 +240,9 @@ static struct attribute * kernel_attrs[]
&rcu_expedited_attr.attr,
&rcu_normal_attr.attr,
#endif
+#ifdef CONFIG_PREEMPT_RT_FULL
+ &realtime_attr.attr,
+#endif
NULL
};
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