ring-buffer: Add ring buffer startup selftest

When testing my large changes to the ftrace system, there was
a bug that looked like the ring buffer was dropping events.
I wrote up a quick integrity checker of the ring buffer to
see if it was.

Although the bug ended up being something stupid I did in ftrace,
and had nothing to do with the ring buffer, I figured if I spent
the time to write up this test, I might as well include it in the
kernel.

I cleaned it up a bit, as the original version was rather ugly.
Not saying this version is pretty, but it's a beauty queen
compared to what I original wrote.

To enable the start up test, set CONFIG_RING_BUFFER_STARTUP_TEST.

Note, it runs for 10 seconds, so it will slow your boot time
by at least 10 more seconds.

What it does is documented in both the comments and the Kconfig
help.

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

1 files changed, 23 insertions, 0 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index f78eab251897..0b5ecf5517fa 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -565,6 +565,29 @@ config RING_BUFFER_BENCHMARK
 
           If unsure, say N.
 
+config RING_BUFFER_STARTUP_TEST
+       bool "Ring buffer startup self test"
+       depends on RING_BUFFER
+       help
+         Run a simple self test on the ring buffer on boot up. Late in the
+         kernel boot sequence, the test will start that kicks off
+         a thread per cpu. Each thread will write various size events
+         into the ring buffer. Another thread is created to send IPIs
+         to each of the threads, where the IPI handler will also write
+         to the ring buffer, to test/stress the nesting ability.
+         If any anomalies are discovered, a warning will be displayed
+         and all ring buffers will be disabled.
+
+         The test runs for 10 seconds. This will slow your boot time
+         by at least 10 more seconds.
+
+         At the end of the test, statics and more checks are done.
+         It will output the stats of each per cpu buffer. What
+         was written, the sizes, what was read, what was lost, and
+         other similar details.
+
+         If unsure, say N
+
 endif # FTRACE
 
 endif # TRACING_SUPPORT