From fc5377668c3d808e1d53c4aee152c836f55c3490 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Thu, 17 Sep 2009 19:35:28 +0200 Subject: tracing: Remove markers Now that the last users of markers have migrated to the event tracer we can kill off the (now orphan) support code. Signed-off-by: Christoph Hellwig Acked-by: Mathieu Desnoyers Cc: Steven Rostedt Cc: Frederic Weisbecker LKML-Reference: <20090917173527.GA1699@lst.de> Signed-off-by: Ingo Molnar --- Documentation/markers.txt | 104 ---------------------------------------------- 1 file changed, 104 deletions(-) delete mode 100644 Documentation/markers.txt (limited to 'Documentation') diff --git a/Documentation/markers.txt b/Documentation/markers.txt deleted file mode 100644 index d2b3d0e91b26..000000000000 --- a/Documentation/markers.txt +++ /dev/null @@ -1,104 +0,0 @@ - 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). 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 - -And, - -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_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(kernel_irq_entry); - /* write data to trace buffers ... */ -} - -* 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 -dmesg -- cgit v1.2.3-59-g8ed1b