linux-kernel - Re: [RFC lockdep 4/4] lockdep/selftest: Add wait context selftests

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Message-ID: <20201208153111.GJ3025@boqun-archlinux>
Date:   Tue, 8 Dec 2020 23:31:11 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, rcu@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC lockdep 4/4] lockdep/selftest: Add wait context selftests

On Tue, Dec 08, 2020 at 03:33:24PM +0100, Peter Zijlstra wrote:
> On Tue, Dec 08, 2020 at 06:31:12PM +0800, Boqun Feng wrote:
> > These tests are added for two purposes:
> > 
> > *	Test the implementation of wait context checks and related
> > 	annotations.
> > 
> > *	Semi-document the rules for wait context nesting when
> > 	PROVE_RAW_LOCK_NESTING=y.
> 
> Documentation/locking/locktypes.rst should have that.
> 

Thanks for the pointer!

I miss it before, and it's really a comprehensive document for lock
nesting rules. Still I think more rules can be (and should be) put in
that document: a broader idea is the context nesting rule (e.g. whether
a spinlock_t is allowed in a hard irq handler). And the document
reminders me that I'm missing some locks (e.g local_lock) in the test
cases. So will improve both the document and the test cases in the next
version. In the meanwhile, feel free to point out any mistake or
misunderstanding of mine in the rules or the tests, I'm really still
learning through these locks with PREEMPT_RT into consideration, thanks!

Regards,
Boqun

> > The test cases are only avaible for PROVE_RAW_LOCK_NESTING=y, as wait
> > context checking makes more sense for that configuration.
> 
> Looks about right ;-)