tracing: Add trace_printk sample code

Add sample code to test trace_printk(). The trace_printk() functions should
never be used in production code. This makes testing it a bit more
difficult. Having a sample module that can test use cases of trace_printk()
can help out.

Currently it just tests trace_printk() where it will be converted into:

 trace_bputs()
 trace_puts()
 trace_bprintk()

as well as staying as the normal _trace_printk().

It also tests its use in interrupt context as that will test the auxilery
buffers.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/samples/Kconfig b/samples/Kconfig
index 559a58baff6ea5be2915ea6ed551a10c7adf3877..27a24571e96cbb456f219d7e24f1c7e5c787410f 100644 (file)
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -11,6 +11,13 @@ config SAMPLE_TRACE_EVENTS
        help
          This build trace event example modules.
 
+config SAMPLE_TRACE_PRINTK
+        tristate "Build trace_printk module - tests various trace_printk formats"
+       depends on EVENT_TRACING && m
+       help
+        This builds a module that calls trace_printk() and can be used to
+        test various trace_printk() calls from a module.
+
 config SAMPLE_KOBJECT
        tristate "Build kobject examples -- loadable modules only"
        depends on m

diff --git a/samples/Makefile b/samples/Makefile
index 2e3b523d7097cb2a6c6a9d46939921c7df3cd8f6..1a20169d85acf9a6e54cdaa0cd83650ac53b7d0c 100644 (file)
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -2,4 +2,4 @@
 
 obj-$(CONFIG_SAMPLES)  += kobject/ kprobes/ trace_events/ livepatch/ \
                           hw_breakpoint/ kfifo/ kdb/ hidraw/ rpmsg/ seccomp/ \
-                          configfs/ connector/ v4l/
+                          configfs/ connector/ v4l/ trace_printk/

diff --git a/samples/trace_printk/Makefile b/samples/trace_printk/Makefile
new file mode 100644 (file)
index 0000000..19900ab
--- /dev/null
+++ b/samples/trace_printk/Makefile
@@ -0,0 +1,6 @@
+# builds a module that calls various trace_printk routines
+# then to use one (as root):  insmod <module_name.ko>
+
+# This module can also be used to test the trace_printk code.
+
+obj-$(CONFIG_SAMPLE_TRACE_PRINTK) += trace-printk.o

diff --git a/samples/trace_printk/trace-printk.c b/samples/trace_printk/trace-printk.c
new file mode 100644 (file)
index 0000000..e9e0040
--- /dev/null
+++ b/samples/trace_printk/trace-printk.c
@@ -0,0 +1,56 @@
+#include <linux/module.h>
+#include <linux/kthread.h>
+#include <linux/irq_work.h>
+
+/* Must not be static to force gcc to consider these non constant */
+char *trace_printk_test_global_str =
+       "This is a dynamic string that will use trace_puts\n";
+
+char *trace_printk_test_global_str_irq =
+       "(irq) This is a dynamic string that will use trace_puts\n";
+
+char *trace_printk_test_global_str_fmt =
+       "%sThis is a %s that will use trace_printk\n";
+
+static struct irq_work irqwork;
+
+static void trace_printk_irq_work(struct irq_work *work)
+{
+       trace_printk("(irq) This is a static string that will use trace_bputs\n");
+       trace_printk(trace_printk_test_global_str_irq);
+
+       trace_printk("(irq) This is a %s that will use trace_bprintk()\n",
+                    "static string");
+
+       trace_printk(trace_printk_test_global_str_fmt,
+                    "(irq) ", "dynamic string");
+}
+
+static int __init trace_printk_init(void)
+{
+       init_irq_work(&irqwork, trace_printk_irq_work);
+
+       trace_printk("This is a static string that will use trace_bputs\n");
+       trace_printk(trace_printk_test_global_str);
+
+       /* Kick off printing in irq context */
+       irq_work_queue(&irqwork);
+
+       trace_printk("This is a %s that will use trace_bprintk()\n",
+                    "static string");
+
+       trace_printk(trace_printk_test_global_str_fmt, "", "dynamic string");
+
+       return 0;
+}
+
+static void __exit trace_printk_exit(void)
+{
+}
+
+module_init(trace_printk_init);
+module_exit(trace_printk_exit);
+
+MODULE_AUTHOR("Steven Rostedt");
+MODULE_DESCRIPTION("trace-printk");
+MODULE_LICENSE("GPL");