path: root/Documentation
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authorAvik Sil <avik.sil@linaro.org>2011-03-31 11:06:38 +0000
committerAvik Sil <avik.sil@linaro.org>2011-03-31 11:06:38 +0000
commitebb688e3183bd5891312bdb8f4e2f520d70b36b6 (patch)
treec30d1abefaccc8cd1baa4944aae3348668e13bde /Documentation
parent8061f3a885ec3538bf405ff3957c205b1ab2aae4 (diff)
parentb2afcd30fff4c24290a63a2497de301864d9726d (diff)
Merge remote branch 'lttng/2.6.38-lttng-0.247'
Conflicts: arch/arm/kernel/traps.c arch/arm/mach-omap2/clock34xx.c arch/arm/mach-omap2/pm34xx.c
Diffstat (limited to 'Documentation')
3 files changed, 118 insertions, 1 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index f4a04c0c7ed..d46f541baf8 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -794,6 +794,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
that can be changed at run time by the
set_graph_function file in the debugfs tracing directory.
+ force_tsc_sync=1
+ Force TSC resynchronization when SMP CPUs go online.
+ See also idle=poll and disable frequency scaling.
[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
support via parallel port (up to 5 devices per port)
diff --git a/Documentation/markers.txt b/Documentation/markers.txt
new file mode 100644
index 00000000000..e25df7cd03b
--- /dev/null
+++ b/Documentation/markers.txt
@@ -0,0 +1,113 @@
+ Using the Linux Kernel Markers
+ Mathieu Desnoyers
+This document introduces Linux Kernel Markers and their use. It provides
+examples of how to insert markers in the kernel and connect probe functions to
+them and provides some examples of probe functions.
+* Purpose of markers
+A marker placed in code provides a hook to call a function (probe) that you can
+provide at runtime. A marker can be "on" (a probe is connected to it) or "off"
+(no probe is attached). When a marker is "off" it has no effect, except for
+adding a tiny time penalty (checking a condition for a branch) and space
+penalty (adding a few bytes for the function call at the end of the
+instrumented function and adds a data structure in a separate section). The
+immediate values are used to minimize the impact on data cache, encoding the
+condition in the instruction stream. When a marker is "on", the function you
+provide is called each time the marker is executed, in the execution context of
+the caller. When the function provided ends its execution, it returns to the
+caller (continuing from the marker site).
+You can put markers at important locations in the code. Markers are
+lightweight hooks that can pass an arbitrary number of parameters,
+described in a printk-like format string, to the attached probe function.
+They can be used for tracing and performance accounting.
+* Usage
+In order to use the macro trace_mark, you should include linux/marker.h.
+#include <linux/marker.h>
+trace_mark(subsystem_event, "myint %d mystring %s", someint, somestring);
+Where :
+- subsystem_event is an identifier unique to your event
+ - subsystem is the name of your subsystem.
+ - event is the name of the event to mark.
+- "myint %d mystring %s" is the formatted string for the serializer. "myint" and
+ "mystring" are repectively the field names associated with the first and
+ second parameter.
+- someint is an integer.
+- somestring is a char pointer.
+Connecting a function (probe) to a marker is done by providing a probe (function
+to call) for the specific marker through marker_probe_register() and can be
+activated by calling marker_arm(). Marker deactivation can be done by calling
+marker_disarm() as many times as marker_arm() has been called. Removing a probe
+is done through marker_probe_unregister(); it will disarm the probe.
+marker_synchronize_unregister() must be called between probe unregistration and
+the first occurrence of
+- the end of module exit function,
+ to make sure there is no caller left using the probe;
+- the free of any resource used by the probes,
+ to make sure the probes wont be accessing invalid data.
+This, and the fact that preemption is disabled around the probe call, make sure
+that probe removal and module unload are safe. See the "Probe example" section
+below for a sample probe module.
+The marker mechanism supports inserting multiple instances of the same marker.
+Markers can be put in inline functions, inlined static functions, and
+unrolled loops as well as regular functions.
+The naming scheme "subsystem_event" is suggested here as a convention intended
+to limit collisions. Marker names are global to the kernel: they are considered
+as being the same whether they are in the core kernel image or in modules.
+Conflicting format strings for markers with the same name will cause the markers
+to be detected to have a different format string not to be armed and will output
+a printk warning which identifies the inconsistency:
+"Format mismatch for probe probe_name (format), marker (format)"
+Another way to use markers is to simply define the marker without generating any
+function call to actually call into the marker. This is useful in combination
+with tracepoint probes in a scheme like this :
+void probe_tracepoint_name(unsigned int arg1, struct task_struct *tsk);
+DEFINE_MARKER_TP(marker_channel, marker_eventname, tracepoint_name,
+ probe_tracepoint_name, "arg1 %u pid %d");
+notrace void probe_tracepoint_name(unsigned int arg1, struct task_struct *tsk)
+ struct marker *marker = &GET_MARKER(marker_channel, marker_eventname);
+ /* write data to trace buffers ... */
+* Optimization for a given architecture
+To force use of a non-optimized version of the markers, _trace_mark() should be
+used. It takes the same parameters as the normal markers, but it does not use
+the immediate values based on code patching.
+* Probe / marker example
+See the example provided in samples/markers/src
+Compile them with your kernel.
+Run, as root :
+modprobe marker-example (insmod order is not important)
+modprobe probe-example
+cat /proc/marker-example (returns an expected error)
+rmmod marker-example probe-example
diff --git a/Documentation/trace/tracepoints.txt b/Documentation/trace/tracepoints.txt
index c0e1ceed75a..d380250339a 100644
--- a/Documentation/trace/tracepoints.txt
+++ b/Documentation/trace/tracepoints.txt
@@ -106,7 +106,7 @@ used to export the defined tracepoints.
See the example provided in samples/tracepoints
Compile them with your kernel. They are built during 'make' (not
-'make modules') when CONFIG_SAMPLE_TRACEPOINTS=m.
+'make modules') when CONFIG_SAMPLE=y and CONFIG_SAMPLE_TRACEPOINTS=m.
Run, as root :
modprobe tracepoint-sample (insmod order is not important)