[openwrt/openwrt] build: Add IRQSOFF and PREEMPT TRACER kernel config option

[LEDE Commits]

hauke pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/1926ffb5ab3ce15e20445f52e6a44a9d9c2295c5

commit 1926ffb5ab3ce15e20445f52e6a44a9d9c2295c5
Author: Hauke Mehrtens <hmehrtens at maxlinear.com>
AuthorDate: Thu Dec 3 18:49:12 2020 +0100

    build: Add IRQSOFF and PREEMPT TRACER kernel config option
    
    This adds the CONFIG_IRQSOFF_TRACER and the CONFIG_PREEMPT_TRACER kernel
    configuration option to the OpenWrt menu. This can be used to debug
    latencies in the system.
    The CONFIG_PREEMPT_TRACER option needs the CONFIG_PREEMPT option which is
    supposed to be used for Low-Latency Desktop and not used by many targets
    in OpenWrt.
    
    The help text is copied from the Linux kernel Kconfig.
    
    Signed-off-by: Hauke Mehrtens <hmehrtens at maxlinear.com>
---
 config/Config-kernel.in | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/config/Config-kernel.in b/config/Config-kernel.in
index 3f013aa2b2..22e2286b8d 100644
--- a/config/Config-kernel.in
+++ b/config/Config-kernel.in
@@ -266,6 +266,40 @@ config KERNEL_FUNCTION_PROFILER
 	depends on KERNEL_FUNCTION_TRACER
 	default n
 
+config KERNEL_IRQSOFF_TRACER
+	bool "Interrupts-off Latency Tracer"
+	depends on KERNEL_FTRACE
+	help
+	  This option measures the time spent in irqs-off critical
+	  sections, with microsecond accuracy.
+
+	  The default measurement method is a maximum search, which is
+	  disabled by default and can be runtime (re-)started
+	  via:
+
+	      echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
+
+	  (Note that kernel size and overhead increase with this option
+	  enabled. This option and the preempt-off timing option can be
+	  used together or separately.)
+
+config KERNEL_PREEMPT_TRACER
+	bool "Preemption-off Latency Tracer"
+	depends on KERNEL_FTRACE
+	help
+	  This option measures the time spent in preemption-off critical
+	  sections, with microsecond accuracy.
+
+	  The default measurement method is a maximum search, which is
+	  disabled by default and can be runtime (re-)started
+	  via:
+
+	      echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
+
+	  (Note that kernel size and overhead increase with this option
+	  enabled. This option and the irqs-off timing option can be
+	  used together or separately.)
+
 config KERNEL_DEBUG_KERNEL
 	bool
 	default n