f9f96ebf13
MFC after: 1 week
195 lines
6.9 KiB
Groff
195 lines
6.9 KiB
Groff
.\"
|
|
.\" Copyright (c) 2015 Netflix Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
|
|
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
|
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
|
.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
|
|
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd November 12, 2015
|
|
.Dt KERN_TESTFRWK 9
|
|
.Os
|
|
.Sh NAME
|
|
.Nm kern_testfrwk
|
|
.Nd A kernel testing framework
|
|
.Sh SYNOPSIS
|
|
kld_load kern_testfrwk
|
|
.Sh DESCRIPTION
|
|
.\" This whole section is not written in manual page style and should be ripped
|
|
.\" out and replaced. -CEM
|
|
So what is this sys/tests directory in the kernel all about?
|
|
.Pp
|
|
Have you ever wanted to test a part of the FreeBSD kernel in some way and you
|
|
had no real way from user-land to make what you want to occur happen?
|
|
Say an error path or situation where locking occurs in a particular manner that
|
|
happens only once in a blue moon?
|
|
.Pp
|
|
If so, then the kernel test framework is just what you are looking for.
|
|
It is designed to help you create the situation you want.
|
|
.Pp
|
|
There are two components to the system: the test framework and your test.
|
|
This document will describe both components and use the test submitted with the
|
|
initial commit of this code to discuss the test
|
|
.Xr ( callout_test 4 ) .
|
|
All of the tests become kernel loadable modules.
|
|
The test you write should have a dependency on the test framework.
|
|
That way it will be loaded automatically with your test.
|
|
For example, you can see how to do this in the bottom of callout_test.c in
|
|
.Pa sys/tests/callout_test/callout_test.c .
|
|
.Pp
|
|
The framework itself is in
|
|
.Pa sys/tests/framework/kern_testfrwk.c .
|
|
Its job is to manage the tests that are loaded.
|
|
(More than one can be loaded.)
|
|
The idea is pretty simple; you load the test framework and then load your test.
|
|
.Pp
|
|
When your test loads, you register your tests with the kernel test framework.
|
|
You do that through a call to
|
|
.Fn kern_testframework_register .
|
|
Usually this is done at the module load event as shown below:
|
|
.Bd -literal -offset indent
|
|
switch (type) {
|
|
case MOD_LOAD:
|
|
err = kern_testframework_register("callout_test",
|
|
run_callout_test);
|
|
.Ed
|
|
.Pp
|
|
Here the test is "callout_test" and it is registered to run the function
|
|
.Fn run_callout_test
|
|
passing it a
|
|
.Fa struct kern_test *ptr .
|
|
The
|
|
.Vt kern_test
|
|
structure is defined in
|
|
.Pa kern_testfrwk.h .
|
|
.Bd -literal -offset indent
|
|
struct kern_test {
|
|
char name[TEST_NAME_LEN];
|
|
int num_threads; /* Fill in how many threads you want */
|
|
int tot_threads_running; /* Private to framework */
|
|
uint8_t test_options[TEST_OPTION_SPACE];
|
|
};
|
|
.Ed
|
|
.Pp
|
|
The user sends this structure down via a sysctl to start your test.
|
|
He or she places the same name you registered ("callout_test"
|
|
in our example) in the
|
|
.Va name
|
|
field.
|
|
The user can also set the number of threads to run with
|
|
.Va num_threads .
|
|
.Pp
|
|
The framework will start the requested number of kernel threads, all running
|
|
your test at the same time.
|
|
The user does not specify anything in
|
|
.Va tot_threads_running ;
|
|
it is private to the framework.
|
|
As the framework calls each of your tests, it will set the
|
|
.Va tot_threads_running
|
|
to the index of the thread that your call is made from.
|
|
For example, if the user sets
|
|
.Va num_threads
|
|
to 2, then the function
|
|
.Fn run_callout_test
|
|
will be called once with
|
|
.Va tot_threads_running
|
|
to 0, and a second time with
|
|
.Va tot_threads_running
|
|
set to 1.
|
|
.Pp
|
|
The
|
|
.Va test_options
|
|
field is a test-specific set of information that is an opaque blob.
|
|
It is passed in from user space and has a maximum size of 256 bytes.
|
|
You can pass arbitrary test input in the space.
|
|
In the case of callout_test we reshape that to:
|
|
.Bd -literal -offset indent
|
|
struct callout_test {
|
|
int number_of_callouts;
|
|
int test_number;
|
|
};
|
|
.Ed
|
|
.Pp
|
|
So the first lines of
|
|
.Fn run_callout_test
|
|
does the following to get at the user specific data:
|
|
.\" This is a bad example and violates strict aliasing. It should be replaced.
|
|
.Bd -literal -offset indent
|
|
struct callout_test *u;
|
|
size_t sz;
|
|
int i;
|
|
struct callout_run *rn;
|
|
int index = test->tot_threads_running;
|
|
|
|
u = (struct callout_test *)test->test_options;
|
|
.Ed
|
|
.Pp
|
|
That way it can access:
|
|
.Va u->test_number
|
|
(there are two types of tests provided with this test)
|
|
and
|
|
.Va u->number_of_callouts
|
|
(how many simultaneous callouts to run).
|
|
.Pp
|
|
Your test can do anything with these bytes.
|
|
So the callout_test in question wants to create a situation where multiple
|
|
callouts are all run, that is the
|
|
.Va number_of_callouts ,
|
|
and it tries to cancel the callout with the new
|
|
.Fn callout_async_drain .
|
|
The threads do this by acquiring the lock in question, and then
|
|
starting each of the callouts.
|
|
It waits for the callouts to all go off (the executor spins waits).
|
|
This forces the situation that the callouts have expired and are all waiting on
|
|
the lock that the executor holds.
|
|
After the callouts are all blocked, the executor calls
|
|
.Fn callout_async_drain
|
|
on each callout and releases the lock.
|
|
.Pp
|
|
.\" callout_test(4) specific documentation should probably be moved to its own
|
|
.\" page.
|
|
After all the callouts are done, a total status is printed
|
|
showing the results via
|
|
.Xr printf 9 .
|
|
The human tester can run
|
|
.Xr dmesg 8
|
|
to see the results.
|
|
In this case it is expected that if you are running test 0, all the callouts
|
|
expire on the same CPU so only one callout_drain function would have been
|
|
called.
|
|
the number of zero_returns should match the number of callout_drains that were
|
|
called, i.e., 1.
|
|
The one_returns should be the remainder of the callouts.
|
|
If the test number was 1, the callouts were spread across all CPUs.
|
|
The number of zero_returns will again match the number of drain calls made
|
|
which matches the number of CPUs that were put in use.
|
|
.Pp
|
|
More than one thread can be used with this test, though in the example case it
|
|
is probably not necessary.
|
|
.Pp
|
|
You should not need to change the framework.
|
|
Just add tests and register them after loading.
|
|
.Sh AUTHORS
|
|
The kernel test framework was written by
|
|
.An Randall Stewart Aq Mt rrs@FreeBSD.org
|
|
with help from
|
|
.An John Mark Gurney Aq Mt jmg@FreeBSD.org .
|