linux-kernel - Re: [PATCH 6/9] lockdep: Introduce wait-type checks

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Message-ID: <73527658125791c2faed1fdfc47dca37e1860493.camel@siemens.com>
Date: Mon, 17 Nov 2025 15:28:39 +0000
From: "Sverdlin, Alexander" <alexander.sverdlin@...mens.com>
To: "o.rempel@...gutronix.de" <o.rempel@...gutronix.de>,
	"bigeasy@...utronix.de" <bigeasy@...utronix.de>
CC: "mingo@...nel.org" <mingo@...nel.org>, "peterz@...radead.org"
	<peterz@...radead.org>, "rostedt@...dmis.org" <rostedt@...dmis.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>, "paulmck@...nel.org"
	<paulmck@...nel.org>, "torvalds@...ux-foundation.org"
	<torvalds@...ux-foundation.org>, "joel@...lfernandes.org"
	<joel@...lfernandes.org>, "will@...nel.org" <will@...nel.org>
Subject: Re: [PATCH 6/9] lockdep: Introduce wait-type checks

Hi Sebstian,

On Mon, 2025-11-17 at 16:13 +0100, bigeasy@...utronix.de wrote:
> > > > > >   counter_push_event+0x68/0x430 [counter]
> > > > > >   interrupt_cnt_isr+0x40/0x78 [interrupt_cnt]
> > > > > >   __handle_irq_event_percpu+0xa4/0x398
> …
> > > Does that help?
> > 
> > Mmm. Not yet... Does this mean we are not allowed to use "spinlock_t" in
> > IRQs any longer? Where has this been announced? This probably means that
> > the majority of IRQ handlers were already converted tree-wide?
> > 
> > This also would mean that spin_lock_irqsave() shall not exist at all
> > so that we are forced to use raw_spin_lock_irqsave()?
> 
> As I tried to explain, if you use IRQF_NO_THREAD then the handler will
> not be threaded. Looking at drivers/counter/interrupt-cnt.c, it does
> 
> >          irq_set_status_flags(priv->irq, IRQ_NOAUTOEN);
> >          ret = devm_request_irq(dev, priv->irq, interrupt_cnt_isr,
> >                                 IRQF_TRIGGER_RISING | IRQF_NO_THREAD,
> >                                 dev_name(dev), counter);
> >          if (ret)
> 
> So the irq-core does not thread the handler as requested. So it must not
> use spinlock_t in such a case.
> And judging from the code, that IRQF_NO_THREAD should be removed. Not
> sure why you are the only seeing that splat.

thanks for looking into that! I've totally missed IRQF_NO_THREAD!
I'll post a patch removing it...

-- 
Alexander Sverdlin
Siemens AG
www.siemens.com