linux-kernel - Re: [PATCH v3] kunit: added lockdep support

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Date:   Sat, 15 Aug 2020 10:30:29 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Uriel Guajardo <urielguajardojr@...il.com>
Cc:     brendanhiggins@...gle.com, peterz@...radead.org, mingo@...hat.com,
        will@...nel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com,
        urielguajardo@...gle.com, alan.maguire@...cle.com
Subject: Re: [PATCH v3] kunit: added lockdep support


* Uriel Guajardo <urielguajardojr@...il.com> wrote:

> From: Uriel Guajardo <urielguajardo@...gle.com>
> 
> KUnit will fail tests upon observing a lockdep failure. Because lockdep
> turns itself off after its first failure, only fail the first test and
> warn users to not expect any future failures from lockdep.
> 
> Similar to lib/locking-selftest [1], we check if the status of
> debug_locks has changed after the execution of a test case. However, we
> do not reset lockdep afterwards.
> 
> Like the locking selftests, we also fix possible preemption count
> corruption from lock bugs.

> --- a/lib/kunit/Makefile
> +++ b/lib/kunit/Makefile

> +void kunit_check_lockdep(struct kunit *test, struct kunit_lockdep *lockdep) {
> +	int saved_preempt_count = lockdep->preempt_count;
> +	bool saved_debug_locks = lockdep->debug_locks;
> +
> +	if (DEBUG_LOCKS_WARN_ON(preempt_count() != saved_preempt_count))
> +		preempt_count_set(saved_preempt_count);
> +
> +#ifdef CONFIG_TRACE_IRQFLAGS
> +	if (softirq_count())
> +		current->softirqs_enabled = 0;
> +	else
> +		current->softirqs_enabled = 1;
> +#endif
> +
> +	if (saved_debug_locks && !debug_locks) {
> +		kunit_set_failure(test);
> +		kunit_warn(test, "Dynamic analysis tool failure from LOCKDEP.");
> +		kunit_warn(test, "Further tests will have LOCKDEP disabled.");
> +	}


So this basically duplicates what the boot-time locking self-tests do, 
in a poor fashion?

Instead of duplicating unit tests, the right solution would be to 
generalize the locking self-tests and use them both during bootup and 
in kunit.

Thanks,

	Ingo