From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from metis.whiteo.stw.pengutronix.de (metis.whiteo.stw.pengutronix.de [185.203.201.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0FEEF2EA743 for ; Tue, 18 Nov 2025 09:54:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.203.201.7 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763459691; cv=none; b=j/NhdUV6j1wrVVjpKFjUlUzcnQTKymWojHhC2l+kx2xL+v2mcqoBhDQqk3AsCz1Xmok7bLWgJvj1v2cF6zSbygyJ8FXXAKilnfPMGMhxKtlNg7dpR4vPW3RPJ7IA4anMYVYJRtz6fOmDlI0I3MBPYyNql2rSgG1i9/itPhk70FM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763459691; c=relaxed/simple; bh=04lIDrwEueqoNF1FBuMpRNyxK8Qa6McA1a3QAb2yqGQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=DnKNUbVupw1UHvEMbUCKXaIegapLpVAie4I6EAFtrLdrBy/FyiN0iDwSiJ2s+4GCWp7CUgabuAFU9BkjPefFPpC/RkKBf1KymCHWpuPwX82tuJIcoiniY1dqdIbTaQKcYrHTkF3DfFtHsJe10uJdk2An7zOa9syNMfvikSecXUY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de; spf=pass smtp.mailfrom=pengutronix.de; arc=none smtp.client-ip=185.203.201.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=pengutronix.de Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1vLIPe-0002Fj-NI; Tue, 18 Nov 2025 10:54:14 +0100 Received: from pty.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::c5]) by drehscheibe.grey.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1vLIPd-0013pp-2g; Tue, 18 Nov 2025 10:54:13 +0100 Received: from ore by pty.whiteo.stw.pengutronix.de with local (Exim 4.96) (envelope-from ) id 1vLIPd-00AAvN-2F; Tue, 18 Nov 2025 10:54:13 +0100 Date: Tue, 18 Nov 2025 10:54:13 +0100 From: Oleksij Rempel To: "Sverdlin, Alexander" Cc: "a.fatoum@pengutronix.de" , "kernel@pengutronix.de" , "linux-iio@vger.kernel.org" , "Jonathan.Cameron@huawei.com" , "wbg@kernel.org" , "linux-kernel@vger.kernel.org" , "paulmck@kernel.org" , "bigeasy@linutronix.de" , "stable@vger.kernel.org" Subject: Re: [PATCH] counter: interrupt-cnt: Drop IRQF_NO_THREAD flag Message-ID: References: <20251118083603.778626-1-alexander.sverdlin@siemens.com> Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: ore@pengutronix.de X-SA-Exim-Scanned: No (on metis.whiteo.stw.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-iio@vger.kernel.org On Tue, Nov 18, 2025 at 09:51:02AM +0000, Sverdlin, Alexander wrote: > Hi Oleksij! > > On Tue, 2025-11-18 at 10:12 +0100, Oleksij Rempel wrote: > > > An IRQ handler can either be IRQF_NO_THREAD or acquire spinlock_t, as > > > CONFIG_PROVE_RAW_LOCK_NESTING warns: > > > ============================= > > > [ BUG: Invalid wait context ] > > > 6.18.0-rc1+git... #1 > > > ----------------------------- > > > some-user-space-process/1251 is trying to lock: > > > (&counter->events_list_lock){....}-{3:3}, at: counter_push_event [counter] > > > other info that might help us debug this: > > > context-{2:2} > > > no locks held by some-user-space-process/.... > > > stack backtrace: > > > CPU: 0 UID: 0 PID: 1251 Comm: some-user-space-process 6.18.0-rc1+git... #1 PREEMPT > > > Call trace: > > >   show_stack (C) > > >   dump_stack_lvl > > >   dump_stack > > >   __lock_acquire > > >   lock_acquire > > >   _raw_spin_lock_irqsave > > >   counter_push_event [counter] > > >   interrupt_cnt_isr [interrupt_cnt] > > >   __handle_irq_event_percpu > > >   handle_irq_event > > >   handle_simple_irq > > >   handle_irq_desc > > >   generic_handle_domain_irq > > >   gpio_irq_handler > > >   handle_irq_desc > > >   generic_handle_domain_irq > > >   gic_handle_irq > > >   call_on_irq_stack > > >   do_interrupt_handler > > >   el0_interrupt > > >   __el0_irq_handler_common > > >   el0t_64_irq_handler > > >   el0t_64_irq > > > > > > ... and Sebastian correctly points out. Remove IRQF_NO_THREAD as an > > > alternative to switching to raw_spinlock_t, because the latter would limit > > > all potential nested locks to raw_spinlock_t only. > > > > > > Cc: Sebastian Andrzej Siewior > > > Cc: stable@vger.kernel.org > > > Link: https://lore.kernel.org/all/20251117151314.xwLAZrWY@linutronix.de/ > > > Fixes: a55ebd47f21f ("counter: add IRQ or GPIO based counter") > > > Signed-off-by: Alexander Sverdlin > > > --- > > >   drivers/counter/interrupt-cnt.c | 3 +-- > > >   1 file changed, 1 insertion(+), 2 deletions(-) > > > > > > diff --git a/drivers/counter/interrupt-cnt.c b/drivers/counter/interrupt-cnt.c > > > index 6c0c1d2d7027d..e6100b5fb082e 100644 > > > --- a/drivers/counter/interrupt-cnt.c > > > +++ b/drivers/counter/interrupt-cnt.c > > > @@ -229,8 +229,7 @@ static int interrupt_cnt_probe(struct platform_device *pdev) > > >   > > >    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); > > > +        IRQF_TRIGGER_RISING, dev_name(dev), counter); > > >    if (ret) > > >    return ret; > > >   > > > > Hm, I guess it will break the requirement to handle at least 10kHz > > interrupts. May be we should move only counter_push_event() to the > > thread? or using delayed worker? > > > > Right now I do not have needed system for testing to come with better > > proposal. > > I thought about possible performance implications of the patch. > But the performance regression would happen only with PREEMPT_RT. > However, it must have been broken (and by that I mean really broken, like > "scheduling in atomic") from the very beginning in PREEMPT_RT and > I suppose your initial tests were performed not with PREEMPT_RT kernel. Ack. > So overall there shall be no possible performance regression in reality. Ok, thank you! Reviewed-by: Oleksij Rempel -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |