linux-kernel - Re: [RFC PATCH 1/3] lockdep/irq: Be more strict about IRQ-threadable code end

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Message-ID: <20200323153039.GA5755@lenoir>
Date:   Mon, 23 Mar 2020 16:30:40 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH 1/3] lockdep/irq: Be more strict about IRQ-threadable
 code end

On Mon, Mar 23, 2020 at 02:53:20PM +0100, Peter Zijlstra wrote:
> On Mon, Mar 23, 2020 at 04:32:05AM +0100, Frederic Weisbecker wrote:
> > --- a/kernel/irq/handle.c
> > +++ b/kernel/irq/handle.c
> > @@ -144,18 +144,24 @@ irqreturn_t __handle_irq_event_percpu(struct irq_desc *desc, unsigned int *flags
> >  
> >  	for_each_action_of_desc(desc, action) {
> >  		irqreturn_t res;
> > +		bool threadable;
> >  
> >  		/*
> >  		 * If this IRQ would be threaded under force_irqthreads, mark it so.
> >  		 */
> > -		if (irq_settings_can_thread(desc) &&
> > -		    !(action->flags & (IRQF_NO_THREAD | IRQF_PERCPU | IRQF_ONESHOT)))
> > +		threadable = (irq_settings_can_thread(desc) &&
> > +			      !(action->flags & (IRQF_NO_THREAD | IRQF_PERCPU | IRQF_ONESHOT)));
> > +
> > +		if (threadable)
> >  			trace_hardirq_threaded();
> >  
> >  		trace_irq_handler_entry(irq, action);
> >  		res = action->handler(irq, action->dev_id);
> >  		trace_irq_handler_exit(irq, action, res);
> >  
> > +		if (threadable)
> > +			trace_hardirq_unthreaded();
> 
> AFAICT this doesn't work for nested IRQ handlers.

So current->hardirq_threaded should be a counter perhaps?

> 
> >  		if (WARN_ONCE(!irqs_disabled(),"irq %u handler %pS enabled interrupts\n",
> >  			      irq, action->handler))
> >  			local_irq_disable();
> > -- 
> > 2.25.0
> >