From: Stephen Boyd <sboyd@kernel.org>
To: Brendan Higgins <brendanhiggins@google.com>
Cc: Frank Rowand <frowand.list@gmail.com>,
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Subject: Re: [PATCH v5 01/18] kunit: test: add KUnit test runner core
Date: Tue, 25 Jun 2019 20:40:59 -0700 [thread overview]
Message-ID: <20190626034100.B238520883@mail.kernel.org> (raw)
In-Reply-To: <CAFd5g46Jhxsz6_VXHEVYvTeDRwwzgKpr=aUWLL5b3S4kUukb8g@mail.gmail.com>
Quoting Brendan Higgins (2019-06-25 13:28:25)
> On Wed, Jun 19, 2019 at 5:15 PM Stephen Boyd <sboyd@kernel.org> wrote:
> >
> > Quoting Brendan Higgins (2019-06-17 01:25:56)
> > > diff --git a/kunit/test.c b/kunit/test.c
> > > new file mode 100644
> > > index 0000000000000..d05d254f1521f
> > > --- /dev/null
> > > +++ b/kunit/test.c
> > > @@ -0,0 +1,210 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > > + * Base unit test (KUnit) API.
> > > + *
> > > + * Copyright (C) 2019, Google LLC.
> > > + * Author: Brendan Higgins <brendanhiggins@google.com>
> > > + */
> > > +
> > > +#include <linux/sched/debug.h>
> > > +#include <kunit/test.h>
> > > +
> > > +static bool kunit_get_success(struct kunit *test)
> > > +{
> > > + unsigned long flags;
> > > + bool success;
> > > +
> > > + spin_lock_irqsave(&test->lock, flags);
> > > + success = test->success;
> > > + spin_unlock_irqrestore(&test->lock, flags);
> >
> > I still don't understand the locking scheme in this code. Is the
> > intention to make getter and setter APIs that are "safe" by adding in a
> > spinlock that is held around getting and setting various members in the
> > kunit structure?
>
> Yes, your understanding is correct. It is possible for a user to write
> a test such that certain elements may be updated in different threads;
> this would most likely happen in the case where someone wants to make
> an assertion or an expectation in a thread created by a piece of code
> under test. Although this should generally be avoided, it is possible,
> and there are occasionally good reasons to do so, so it is
> functionality that we should support.
>
> Do you think I should add a comment to this effect?
No, I think the locking should be removed.
>
> > In what situation is there more than one thread reading or writing the
> > kunit struct? Isn't it only a single process that is going to be
>
> As I said above, it is possible that the code under test may spawn a
> new thread that may make an expectation or an assertion. It is not a
> super common use case, but it is possible.
Sure, sounds super possible and OK.
>
> > operating on this structure? And why do we need to disable irqs? Are we
> > expecting to be modifying the unit tests from irq contexts?
>
> There are instances where someone may want to test a driver which has
> an interrupt handler in it. I actually have (not the greatest) example
> here. Now in these cases, I expect someone to use a mock irqchip or
> some other fake mechanism to trigger the interrupt handler and not
> actual hardware; technically speaking in this case, it is not going to
> be accessed from a "real" irq context; however, the code under test
> should think that it is in an irq context; given that, I figured it is
> best to just treat it as a real irq context. Does that make sense?
Can you please describe the scenario in which grabbing the lock here,
updating a single variable, and then releasing the lock right after
does anything useful vs. not having the lock? I'm looking for a two CPU
scenario like below, but where it is a problem. There could be three
CPUs, or even one CPU and three threads if you want to describe the
extra thread scenario.
Here's my scenario where it isn't needed:
CPU0 CPU1
---- ----
kunit_run_test(&test)
test_case_func()
....
[mock hardirq]
kunit_set_success(&test)
[hardirq ends]
...
complete(&test_done)
wait_for_completion(&test_done)
kunit_get_success(&test)
We don't need to care about having locking here because success or
failure only happens in one place and it's synchronized with the
completion.
>
> > > +
> > > + return success;
> > > +}
> > > +
> > > +static void kunit_set_success(struct kunit *test, bool success)
> > > +{
> > > + unsigned long flags;
> > > +
> > > + spin_lock_irqsave(&test->lock, flags);
> > > + test->success = success;
> > > + spin_unlock_irqrestore(&test->lock, flags);
> > > +}
next prev parent reply other threads:[~2019-06-26 3:41 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-17 8:25 [PATCH v5 00/18] kunit: introduce KUnit, the Linux kernel unit testing framework Brendan Higgins
2019-06-17 8:25 ` [PATCH v5 01/18] kunit: test: add KUnit test runner core Brendan Higgins
2019-06-20 0:15 ` Stephen Boyd
2019-06-25 20:28 ` Brendan Higgins
2019-06-25 21:44 ` Luis Chamberlain
2019-06-25 22:14 ` Brendan Higgins
2019-06-25 23:02 ` Luis Chamberlain
2019-06-26 6:41 ` Brendan Higgins
2019-06-26 22:02 ` Luis Chamberlain
2019-06-27 0:05 ` Brendan Higgins
2019-06-26 3:40 ` Stephen Boyd [this message]
2019-06-26 23:00 ` Brendan Higgins
2019-06-27 18:16 ` Stephen Boyd
2019-06-28 8:09 ` Brendan Higgins
2019-06-25 22:33 ` Luis Chamberlain
2019-06-26 0:07 ` Brendan Higgins
2019-06-26 3:36 ` Luis Chamberlain
2019-06-26 22:16 ` Brendan Higgins
2019-06-17 8:25 ` [PATCH v5 02/18] kunit: test: add test resource management API Brendan Higgins
2019-06-17 8:25 ` [PATCH v5 03/18] kunit: test: add string_stream a std::stream like string builder Brendan Higgins
2019-06-17 8:25 ` [PATCH v5 04/18] kunit: test: add kunit_stream a std::stream like logger Brendan Higgins
2019-06-17 8:26 ` [PATCH v5 05/18] kunit: test: add the concept of expectations Brendan Higgins
2019-06-17 8:26 ` [PATCH v5 06/18] kbuild: enable building KUnit Brendan Higgins
2019-06-25 22:13 ` Luis Chamberlain
2019-06-25 22:41 ` Brendan Higgins
2019-06-25 23:03 ` Luis Chamberlain
2019-06-17 8:26 ` [PATCH v5 07/18] kunit: test: add initial tests Brendan Higgins
2019-06-25 23:22 ` Luis Chamberlain
2019-06-26 7:53 ` Brendan Higgins
2019-07-02 17:52 ` Brendan Higgins
2019-07-02 20:57 ` Luis Chamberlain
2019-06-17 8:26 ` [PATCH v5 08/18] objtool: add kunit_try_catch_throw to the noreturn list Brendan Higgins
2019-06-17 8:26 ` [PATCH v5 09/18] kunit: test: add support for test abort Brendan Higgins
2019-06-17 8:26 ` [PATCH v5 10/18] kunit: test: add tests for kunit " Brendan Higgins
2019-06-17 8:26 ` [PATCH v5 11/18] kunit: test: add the concept of assertions Brendan Higgins
2019-06-17 8:26 ` [PATCH v5 12/18] kunit: test: add tests for KUnit managed resources Brendan Higgins
2019-06-17 8:26 ` [PATCH v5 13/18] kunit: tool: add Python wrappers for running KUnit tests Brendan Higgins
2019-06-26 0:01 ` Luis Chamberlain
2019-06-26 8:02 ` Brendan Higgins
2019-06-26 22:03 ` Luis Chamberlain
2019-06-27 0:23 ` Brendan Higgins
2019-06-17 8:26 ` [PATCH v5 14/18] kunit: defconfig: add defconfigs for building " Brendan Higgins
2019-06-17 8:26 ` [PATCH v5 15/18] Documentation: kunit: add documentation for KUnit Brendan Higgins
2019-06-17 8:26 ` [PATCH v5 16/18] MAINTAINERS: add entry for KUnit the unit testing framework Brendan Higgins
2019-06-17 8:26 ` [PATCH v5 17/18] kernel/sysctl-test: Add null pointer test for sysctl.c:proc_dointvec() Brendan Higgins
2019-06-26 2:17 ` Luis Chamberlain
2019-06-27 4:07 ` Iurii Zaikin
2019-06-27 6:10 ` Luis Chamberlain
2019-06-28 8:01 ` Brendan Higgins
2019-06-28 21:37 ` Luis Chamberlain
2019-06-17 8:26 ` [PATCH v5 18/18] MAINTAINERS: add proc sysctl KUnit test to PROC SYSCTL section Brendan Higgins
2019-06-26 2:19 ` Luis Chamberlain
2019-06-20 1:17 ` [PATCH v5 00/18] kunit: introduce KUnit, the Linux kernel unit testing framework Frank Rowand
2019-06-21 14:59 ` shuah
2019-06-21 18:13 ` Theodore Ts'o
2019-06-21 19:20 ` shuah
2019-06-22 0:54 ` Brendan Higgins
2019-07-03 23:40 ` Brendan Higgins
2019-06-21 23:35 ` Brendan Higgins
2019-06-26 2:38 ` Luis Chamberlain
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