From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 B6E493346A5 for ; Tue, 5 May 2026 09:39:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777973994; cv=none; b=uEkdOEdf3C2e4nxAhTXuFOwqG/rLzocYaguZewt2oeRIdGcr6WAxt5nTDvKaX+x4KfT8ESF7EcdToEYJtr159aREErecQCu0623Q6GOhTjVLTEgcJmeYRnIDEZk3ZYI2YVBKMfjI8KhBd8MwOZh51bE4xN8AZuIaCA5jAfW0DO0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777973994; c=relaxed/simple; bh=pXWil8ibvG15Q8+3JxUm9O4lJcLqf9F/Aer9XZ+zJX0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=cHDOabFA1WWuUikaPiwGCw8gMjayutLZ/fFfN74g3+4ONiIY4D4e9z5v2nS5KkS9bYRZVZyavn2KyQugxxW84g967iaJF3+khdrdb8M24OGGVT/NAAyINVdgoJupzfnJfyWD3bTfa742W79vcK9gseIdWs0be6lKfh/w1u/lYE8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mbDD/Pwh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mbDD/Pwh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4C53BC2BCB4; Tue, 5 May 2026 09:39:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777973994; bh=pXWil8ibvG15Q8+3JxUm9O4lJcLqf9F/Aer9XZ+zJX0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=mbDD/PwhHZvBbiXqvrZ829g7Zr0GlAam2Cbodb21mf0/2oO39lrnHVPdhYYYUxR7+ 0lcxgYNt/PFSQlS8XlS8KkJpQq9QSP4rw2MDFXpPaRS+zoiAP0U8CRSYp+55qw8kYs A2R9x3Zo5frHpeErQ9fJ/Rs7aqXc21MG45N4+QXu/F3EOEs6x1O+jvnboJfh7VgycL y03c6y41I4Bhg2FPhep+VPOuyDsY3X1U6W9W4qDPnj1lqC0z8NeEryUjPHfPqnp8c5 EbSMnEa5H+PfPWs8WEYY+NQrobukbVsX2G3VzHPRcobkbeVwddlsKDfwR1BFEGeAL7 LFaZhyN5B5Zyg== Message-ID: <3df439b7-2c28-44f5-81ed-5d4747e7096f@kernel.org> Date: Tue, 5 May 2026 11:39:51 +0200 Precedence: bulk X-Mailing-List: linux-gpio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC] pinctrl: intel: Stop setting IRQF_NO_THREAD ? To: Andy Shevchenko , Mika Westerberg Cc: Andy Shevchenko , Linus Walleij , linux-gpio@vger.kernel.org References: <18ab52bd-9171-4667-a600-0f52ab7017ac@kernel.org> <20250623061517.GU2824380@black.fi.intel.com> From: Hans de Goede Content-Language: en-US, nl In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Andy, On 5-May-26 11:10, Andy Shevchenko wrote: > On Mon, Jun 23, 2025 at 09:15:17AM +0300, Mika Westerberg wrote: >> On Sat, Jun 21, 2025 at 10:49:33AM +0200, Hans de Goede wrote: > >>> While debugging the following lockdep report: >>> >>> ============================= >>> [ BUG: Invalid wait context ] >>> ... >>> swapper/10/0 is trying to lock: >>> ffff88819c271888 (&tp->xfer_wait){....}-{3:3}, >>> at: __wake_up (kernel/sched/wait.c:106 kernel/sched/wait.c:127) >>> ... >>> Call Trace: >>> >>> ... >>> __raw_spin_lock_irqsave (./include/linux/spinlock_api_smp.h:111) >>> __wake_up (kernel/sched/wait.c:106 kernel/sched/wait.c:127) >>> vsc_tp_isr (drivers/misc/mei/vsc-tp.c:110) mei_vsc_hw >>> __handle_irq_event_percpu (kernel/irq/handle.c:158) >>> handle_irq_event (kernel/irq/handle.c:195 kernel/irq/handle.c:210) >>> handle_edge_irq (kernel/irq/chip.c:833) >>> ... >>> >>> >>> I realized after a while that the root-cause here is the IRQF_NO_THREAD >>> usage in pinctrl-intel.c. This was introduced in 1a7d1cb81eb2 ("pinctrl: >>> intel: Prevent force threading of the interrupt handler") to avoid problems >>> caused by using request_irq() for what should be a chained irq handler >>> (which itself is a workaround because of a shared IRQ on some platforms). >>> >>> Generally speaking using IRQF_NO_THREAD is undesirable for 2 reasons: >>> >>> 1. It introduces extra latency on PREEMPT-RT kernels >>> 2. Setting IRQF_NO_THREAD requires all interrupt handlers for GPIO >>> interrupts to use raw-spinlocks only since normal spinlocks can >>> sleep in PREEMPT-RT kernels and with IRQF_NO_THREAD the interrupt >>> handlers will run in an atomic context >>> >>> 2. is what is causing the lockdep report above, by simply using a >>> wake_up(&wq_head) call in an interrupt handler, since wait-queues >>> use normal spinlocks not raw spinlocks. >>> >>> I've tried just removing the IRQF_NO_THREAD flag and that fixes >>> the lockdep report. I've also tried reproducing the problem for >>> which the flag was added in commit 1a7d1cb81eb2 by using a kernel >>> with CONFIG_IRQ_FORCED_THREADING and "threadirqs" on the kernel >>> commandline. And the problem not reproduce. I'm not sure this is >>> 100% proof that the flag is no longer necessary though ... >> >> Can you try also with CONFIG_PREEMPT_RT and see if that triggers the issue? >> If not then: >> >>> So 2 questions: >>> >>> 1. Should we maybe just drop the flag ? >>> 2. Or should we have 2 different code-paths for GPIO controllers >>> with/without shared IRQs and use a chained-irq approach for the >>> not shared case, to at least reduce the usage of the flag ? >> >> I would just drop the flag then. > > Hans, any conclusion on this? I worked around this issue in the affected driver. I have not looked further into actually dropping IRQF_NO_THREAD from the Intel pinctrl/ GPIO drivers. I do think that dropping IRQF_NO_THREAD from the Intel pinctrl/GPIO drivers is probably a good idea, but this will need someone to drive this forward including dealing with any regressions this may lead to. Regards, Hans