linux-kernel - Re: [PATCH tip/core/rcu 06/19] rcu: Add warning to detect half-interrupts

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Message-Id: <20190313180730.GU13351@linux.ibm.com>
Date:   Wed, 13 Mar 2019 11:07:30 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Joel Fernandes <joel@...lfernandes.org>,
        linux-kernel@...r.kernel.org, rcu@...r.kernel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        mathieu.desnoyers@...icios.com, josh@...htriplett.org,
        luto@...nel.org, byungchul.park@....com
Subject: Re: [PATCH tip/core/rcu 06/19] rcu: Add warning to detect
 half-interrupts

On Wed, Mar 13, 2019 at 12:51:25PM -0400, Steven Rostedt wrote:
> On Wed, 13 Mar 2019 08:51:55 -0700
> "Paul E. McKenney" <paulmck@...ux.ibm.com> wrote:
> 
> > Does this mean that there is a better approach that Joel's suggestion?
> > I believe he would end up with something like this:
> > 
> > 	WARN_ON_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && !in_irq());
> > 
> > It would be nice if there is something like this:
> > 
> > 	lockdep_assert_in_irq_handler();
> > 
> > But I haven't seen this.  (Not that I have looked particularly hard for
> > such a thing, mind you!)
> 
> That would be trivial to implement:
> 
> #define lockdep_assert_in_irq() do {
> 		WARN_ON(debug_locks && !current->hardirq_context);
> 	} while (0)

Looks good to me!

Joel, does this work for you?  I could be wrong, but I suspect that Steve
is suggesting that you incorporate the above into your eventual patch.  ;-)

							Thanx, Paul