From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 1D3A3481650; Fri, 4 Sep 2026 13:38:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788529100; cv=none; b=kzzPSAarbLsWkCzg5ETHSRPb7yJX843Jxazj1A2LNR/eUGCIFEFSMGoJYgFLT9Yt8NXA9BVyE0MnjMkh90zL/WrSQHJfy984xWrC80Y+mlJ1gIScZrUnjeb//DEAViac5OgHWBUUZa+uSkOsT9ERe27LoAVk0PdctvPGV2kspys= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788529100; c=relaxed/simple; bh=S8m151s5d1xnf5HLA4fOnXWVZvWn3GVZ8dF3521nopA=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=ZSI+NqYMwuDvyTZRqWXYQcRdwUv8TikH1XYEA/0XUhR9vb2FTtfYWOzUOCvaLJmLRQh1DezPjdiBTFaMXmCelwAsNCVCQmntVsgpkBf3BmMMPGiFJ2ZCxdPis6XFh5HXeG2VykwkQ0OKROc3paMx+8W4MGhrH1zc3kjJWg/73as= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bxUcu7dw; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bxUcu7dw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A4B791F00A3D; Fri, 4 Sep 2026 13:38:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788529098; bh=Bruh2vl+R4oOMZk7fJd+aHtzf3TUbalFwgoHSNuqAwc=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=bxUcu7dwF8RFPTmk5viCVWbKFUiVjWW5ZMvD09sDEFKcO9+C/kc0q48S72Iw0hTPt qYejGUfLuhsuk4/uC5PaJ7OkbsykbgxGuB51YBQBx2QB7yVJWc4GEMOkEhMKRRivMo gaA7lE10TAUdmvy0cfnb8G188AgudVFm0ksYyCbMQlTDaJomSB4sYfGWLfxPe60n2t gxa+AIczvSelGe01IMBDG8ceNbveaN+yWw+sieIMhsSlR606Mky+VrAXfTqknPQgFb tnePVJfI+38DrcuujJPodJI2FTU50wDav9XXVRiLYiXP0Mp1LeTea2NvYBDz/K0LJu J6L+khA/Htqqg== Received: from sofa.misterjones.org ([185.219.108.64] helo=lobster-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1x2U7U-00000004sGq-1lgr; Fri, 04 Sep 2026 13:38:16 +0000 Date: Fri, 04 Sep 2026 14:40:50 +0100 Message-ID: <87wlt13zj1.wl-maz@kernel.org> From: Marc Zyngier To: Thomas Gleixner Cc: Mayank Rungta , Wim Van Sebroeck , Guenter Roeck , Radu Rendec , linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, "Kirill A. Shutemov" , Douglas Anderson Subject: Re: [PATCH v3 1/5] genirq: Synchronize in-flight handlers during NMI teardown In-Reply-To: <87fqzp8jex.ffs@fw13> References: <20260902-qcom-wdt-nmi-series-v3-0-f3999362a9ea@google.com> <20260902-qcom-wdt-nmi-series-v3-1-f3999362a9ea@google.com> <87fqzp8jex.ffs@fw13> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: tglx@kernel.org, mrungta@google.com, wim@linux-watchdog.org, linux@roeck-us.net, radu@rendec.net, linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, kas@kernel.org, dianders@chromium.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Fri, 04 Sep 2026 10:17:42 +0100, Thomas Gleixner wrote: > > On Wed, Sep 02 2026 at 18:54, Mayank Rungta wrote: > > diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c > > index 2fbff2618a1e..a9973b61163a 100644 > > --- a/kernel/irq/manage.c > > +++ b/kernel/irq/manage.c > > @@ -1379,6 +1379,14 @@ static bool irq_supports_nmi(struct irq_desc *desc) > > if (d->chip->irq_bus_lock || d->chip->irq_bus_sync_unlock) > > return false; > > > > + /* > > + * NMIs cannot set IRQD_IRQ_INPROGRESS because they cannot acquire > > + * spinlocks. Synchronous disable and teardown require querying the > > + * hardware state via ->irq_get_irqchip_state(). > > + */ > > + if (!d->chip->irq_get_irqchip_state) > > + return false; > > + > > return d->chip->flags & IRQCHIP_SUPPORTS_NMI; > > } > > > > @@ -2034,11 +2042,20 @@ static const void *__cleanup_nmi(unsigned int irq, struct irq_desc *desc) > > struct irqaction *action = NULL; > > const char *devname = NULL; > > > > + guard(mutex)(&desc->request_mutex); > > + > > scoped_guard(raw_spinlock_irqsave, &desc->lock) { > > - irq_nmi_teardown(desc); > > + irq_settings_clr_disable_unlazy(desc); > > + irq_shutdown(desc); > > + } > > > > - desc->istate &= ~IRQS_NMI; > > + /* > > + * Ensure all in-flight NMI handlers on other CPUs complete before > > + * clearing desc->action or tearing down NMI state. > > + */ > > + __synchronize_hardirq(desc, true); > > NMIs are strictly per CPU interrupts. So how is this supposed to work > correctly when looking at irqchip_state(ACTIVE) ? > > Marc? I have no idea what this is trying to achieve. This can only work for a global interrupt, not for a CPU-private interrupt, since in general you can't observe the state of the interrupt on another CPU. My guess is that the OP is trying to trigger an NMI using a global interrupt, which we never intended to be supported. That's not to say that it cannot be supported, but this patch seems to be breaking the core use case... M. -- Jazz isn't dead. It just smells funny.