From 9cfe06f8cd5c8c3ad6ab323973e87dde670642b8 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Tue, 14 Apr 2009 21:37:03 -0400 Subject: tracing/events: add trace-events-sample This patch adds a sample to the samples directory on how to create and use TRACE_EVENT trace points. Signed-off-by: Steven Rostedt --- samples/Kconfig | 7 ++ samples/Makefile | 2 +- samples/trace_events/Makefile | 8 ++ samples/trace_events/trace-events-sample.c | 56 +++++++++++++ samples/trace_events/trace-events-sample.h | 124 +++++++++++++++++++++++++++++ 5 files changed, 196 insertions(+), 1 deletion(-) create mode 100644 samples/trace_events/Makefile create mode 100644 samples/trace_events/trace-events-sample.c create mode 100644 samples/trace_events/trace-events-sample.h (limited to 'samples') diff --git a/samples/Kconfig b/samples/Kconfig index 4b02f5a0e65..93f41c05109 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -19,6 +19,13 @@ config SAMPLE_TRACEPOINTS help This build tracepoints example modules. +config SAMPLE_TRACE_EVENTS + tristate "Build trace_events examples" + depends on EVENT_TRACING + default m + help + This build trace event example modules. + config SAMPLE_KOBJECT tristate "Build kobject examples" help diff --git a/samples/Makefile b/samples/Makefile index 10eaca89fe1..13e4b470b53 100644 --- a/samples/Makefile +++ b/samples/Makefile @@ -1,3 +1,3 @@ # Makefile for Linux samples code -obj-$(CONFIG_SAMPLES) += markers/ kobject/ kprobes/ tracepoints/ +obj-$(CONFIG_SAMPLES) += markers/ kobject/ kprobes/ tracepoints/ trace_events/ diff --git a/samples/trace_events/Makefile b/samples/trace_events/Makefile new file mode 100644 index 00000000000..06c6dea1eb8 --- /dev/null +++ b/samples/trace_events/Makefile @@ -0,0 +1,8 @@ +# builds the trace events example kernel modules; +# then to use one (as root): insmod + +PWD := $(shell pwd) + +CFLAGS_trace-events-sample.o := -I$(PWD)/samples/trace_events/ + +obj-$(CONFIG_SAMPLE_TRACE_EVENTS) += trace-events-sample.o diff --git a/samples/trace_events/trace-events-sample.c b/samples/trace_events/trace-events-sample.c new file mode 100644 index 00000000000..f33b3ba744a --- /dev/null +++ b/samples/trace_events/trace-events-sample.c @@ -0,0 +1,56 @@ +#include +#include + +/* + * Any file that uses trace points, must include the header. + * But only one file, must include the header by defining + * CREATE_TRACE_POINTS first. This will make the C code that + * creates the handles for the trace points. + */ +#define CREATE_TRACE_POINTS +#include "trace-events-sample.h" + + +static void simple_thread_func(int cnt) +{ + set_current_state(TASK_INTERRUPTIBLE); + schedule_timeout(HZ); + trace_foo_bar("hello", cnt); + + if (!(cnt % 10)) + /* It is really important that I say "hi!" */ + printk(KERN_EMERG "hi!\n"); +} + +static int simple_thread(void *arg) +{ + int cnt = 0; + + while (!kthread_should_stop()) + simple_thread_func(cnt++); + + return 0; +} + +static struct task_struct *simple_tsk; + +static int __init trace_event_init(void) +{ + simple_tsk = kthread_run(simple_thread, NULL, "event-sample"); + if (IS_ERR(simple_tsk)) + return -1; + + return 0; +} + +static void __exit trace_event_exit(void) +{ + kthread_stop(simple_tsk); +} + +module_init(trace_event_init); +module_exit(trace_event_exit); + +MODULE_AUTHOR("Steven Rostedt"); +MODULE_DESCRIPTION("trace-events-sample"); +MODULE_LICENSE("GPL"); diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h new file mode 100644 index 00000000000..eab46443e61 --- /dev/null +++ b/samples/trace_events/trace-events-sample.h @@ -0,0 +1,124 @@ +/* + * Notice that this file is not protected like a normal header. + * We also must allow for rereading of this file. The + * + * || defined(TRACE_HEADER_MULTI_READ) + * + * serves this purpose. + */ +#if !defined(_TRACE_EVENT_SAMPLE_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_EVENT_SAMPLE_H + +/* + * All trace headers should include tracepoint.h, until we finally + * make it into a standard header. + */ +#include + +/* + * If TRACE_SYSTEM is defined, that will be the directory created + * in the ftrace directory under /debugfs/tracing/events/ + * + * The define_trace.h belowe will also look for a file name of + * TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here. + * + * If you want a different system than file name, you can override + * the header name by defining TRACE_INCLUDE_FILE + * + * If this file was called, goofy.h, then we would define: + * + * #define TRACE_INCLUDE_FILE goofy + * + */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM trace-events-sample + +/* + * The TRACE_EVENT macro is broken up into 5 parts. + * + * name: name of the trace point. This is also how to enable the tracepoint. + * A function called trace_foo_bar() will be created. + * + * proto: the prototype of the function trace_foo_bar() + * Here it is trace_foo_bar(char *foo, int bar). + * + * args: must match the arguments in the prototype. + * Here it is simply "foo, bar". + * + * struct: This defines the way the data will be stored in the ring buffer. + * There are currently two types of elements. __field and __array. + * a __field is broken up into (type, name). Where type can be any + * type but an array. + * For an array. there are three fields. (type, name, size). The + * type of elements in the array, the name of the field and the size + * of the array. + * + * __array( char, foo, 10) is the same as saying char foo[10]. + * + * fast_assign: This is a C like function that is used to store the items + * into the ring buffer. + * + * printk: This is a way to print out the data in pretty print. This is + * useful if the system crashes and you are logging via a serial line, + * the data can be printed to the console using this "printk" method. + * + * Note, that for both the assign and the printk, __entry is the handler + * to the data structure in the ring buffer, and is defined by the + * TP_STRUCT__entry. + */ +TRACE_EVENT(foo_bar, + + TP_PROTO(char *foo, int bar), + + TP_ARGS(foo, bar), + + TP_STRUCT__entry( + __array( char, foo, 10 ) + __field( int, bar ) + ), + + TP_fast_assign( + strncpy(__entry->foo, foo, 10); + __entry->bar = bar; + ), + + TP_printk("foo %s %d", __entry->foo, __entry->bar) +); +#endif + +/***** NOTICE! The #if protection ends here. *****/ + + +/* + * There are several ways I could have done this. If I left out the + * TRACE_INCLUDE_PATH, then it would default to the kernel source + * include/trace/events directory. + * + * I could specify a path from the define_trace.h file back to this + * file. + * + * #define TRACE_INCLUDE_PATH ../../samples/trace_events + * + * But I chose to simply make it use the current directory and then in + * the Makefile I added: + * + * CFLAGS_trace-events-sample.o := -I$(PWD)/samples/trace_events/ + * + * This will make sure the current path is part of the include + * structure for our file so that we can find it. + * + * I could have made only the top level directory the include: + * + * CFLAGS_trace-events-sample.o := -I$(PWD) + * + * And then let the path to this directory be the TRACE_INCLUDE_PATH: + * + * #define TRACE_INCLUDE_PATH samples/trace_events + * + * But then if something defines "samples" or "trace_events" then we + * could risk that being converted too, and give us an unexpected + * result. + */ +#undef TRACE_INCLUDE_PATH +#define TRACE_INCLUDE_PATH . +#include -- cgit v1.2.3 From fd6da10a617f483348ee32bcfe53fd20c302eca1 Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Wed, 6 May 2009 10:32:13 +0800 Subject: tracing/events: don't say hi when loading the trace event sample The sample is useful for testing, and I'm using it. But after loading the module, it keeps saying hi every 10 seconds, this may be disturbing. Also Steven said commenting out the "hi" helped in causing races. :) [ Impact: make testing a bit easier ] Signed-off-by: Li Zefan Acked-by: Steven Rostedt Acked-by: Frederic Weisbecker LKML-Reference: <4A00F6AD.2070008@cn.fujitsu.com> Signed-off-by: Ingo Molnar --- samples/trace_events/trace-events-sample.c | 4 ---- 1 file changed, 4 deletions(-) (limited to 'samples') diff --git a/samples/trace_events/trace-events-sample.c b/samples/trace_events/trace-events-sample.c index f33b3ba744a..aabc4e97091 100644 --- a/samples/trace_events/trace-events-sample.c +++ b/samples/trace_events/trace-events-sample.c @@ -16,10 +16,6 @@ static void simple_thread_func(int cnt) set_current_state(TASK_INTERRUPTIBLE); schedule_timeout(HZ); trace_foo_bar("hello", cnt); - - if (!(cnt % 10)) - /* It is really important that I say "hi!" */ - printk(KERN_EMERG "hi!\n"); } static int simple_thread(void *arg) -- cgit v1.2.3 From 96d17980fabeb757706d2d6db5a28580a6156bfc Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Wed, 6 May 2009 10:32:32 +0800 Subject: tracing/events: make SAMPLE_TRACE_EVENTS default to n Normally a config should be default to n. This patch also makes the sample module-only, like SAMPLE_MARKERS and SAMPLE_TRACEPOINTS. [ Impact: don't build trace event sample by default ] Signed-off-by: Li Zefan Acked-by: Steven Rostedt Acked-by: Frederic Weisbecker LKML-Reference: <4A00F6C0.8090803@cn.fujitsu.com> Signed-off-by: Ingo Molnar --- samples/Kconfig | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'samples') diff --git a/samples/Kconfig b/samples/Kconfig index 93f41c05109..b75d28cba3f 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -20,9 +20,8 @@ config SAMPLE_TRACEPOINTS This build tracepoints example modules. config SAMPLE_TRACE_EVENTS - tristate "Build trace_events examples" - depends on EVENT_TRACING - default m + tristate "Build trace_events examples -- loadable modules only" + depends on EVENT_TRACING && m help This build trace event example modules. -- cgit v1.2.3 From 35cf723e99c0e26ddf51f037dffaa4ff2c2c9106 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 6 May 2009 12:33:38 +0200 Subject: tracing: small trave_events sample Makefile cleanup Use -I$(src) to add the current directory the include path. [ Impact: cleanup ] Signed-off-by: Christoph Hellwig Acked-by: Steven Rostedt LKML-Reference: Signed-off-by: Ingo Molnar --- samples/trace_events/Makefile | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'samples') diff --git a/samples/trace_events/Makefile b/samples/trace_events/Makefile index 06c6dea1eb8..0d428dc6728 100644 --- a/samples/trace_events/Makefile +++ b/samples/trace_events/Makefile @@ -1,8 +1,6 @@ # builds the trace events example kernel modules; # then to use one (as root): insmod -PWD := $(shell pwd) - -CFLAGS_trace-events-sample.o := -I$(PWD)/samples/trace_events/ +CFLAGS_trace-events-sample.o := -I$(src) obj-$(CONFIG_SAMPLE_TRACE_EVENTS) += trace-events-sample.o -- cgit v1.2.3 From 71e1c8ac42ae4038ddb1367cce7097ab868dc532 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 6 May 2009 21:20:39 -0400 Subject: tracing: update sample with TRACE_INCLUDE_FILE When creating trace events for ftrace, the header file with the TRACE_EVENT macros must also have a macro called TRACE_SYSTEM. This macro describes the name of the system the TRACE_EVENTS are defined for. It also doubles as a way for the define_trace.h file to include the file that included it. For example: in irq.h #define TRACE_SYSTEM irq [...] #include The define_trace will use TRACE_SYSTEM to include irq.h. But if the name of the trace system does not match the name of the trace header file, one can override it with: Which will change define_trace.h to inclued foo_trace.h instead of foo.h The sample comments this, but people that use the sample code will more likely use the code and not read the comments. This patch changes the sample code to use the TRACE_INCLUDE_FILE to better show developers how to use it. [ Impact: make sample less confusing to developers ] Reported-by: Christoph Hellwig Signed-off-by: Steven Rostedt --- samples/trace_events/trace-events-sample.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'samples') diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h index eab46443e61..128a897687c 100644 --- a/samples/trace_events/trace-events-sample.h +++ b/samples/trace_events/trace-events-sample.h @@ -31,7 +31,7 @@ * */ #undef TRACE_SYSTEM -#define TRACE_SYSTEM trace-events-sample +#define TRACE_SYSTEM sample /* * The TRACE_EVENT macro is broken up into 5 parts. @@ -120,5 +120,10 @@ TRACE_EVENT(foo_bar, * result. */ #undef TRACE_INCLUDE_PATH +#undef TRACE_INCLUDE_FILE #define TRACE_INCLUDE_PATH . +/* + * TRACE_INCLUDE_FILE is not needed if the filename and TRACE_SYSTEM are equal + */ +#define TRACE_INCLUDE_FILE trace-events-sample #include -- cgit v1.2.3