From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [78.32.30.218]) (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 0C2733A7193; Tue, 8 Sep 2026 08:00:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=78.32.30.218 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788854425; cv=none; b=hKcduYdC8XSze8PKkGsmBqsLIggMEauPVwT3i6UyQOKzdyzuykqNYewJP4YMc3bwyWf2p2um+M63hb9Yw6+4rOgFpcxBwQvlW1BPWJ1B1D8UiLupWYczBNdBhIJKGRIGvCV0/7TEfUFwqtZnHyc72WEGsXsTNaThKK9XTuofo4Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788854425; c=relaxed/simple; bh=S/Lz+xHDUUf0g02gnrz++amUF5ofMaisuGHvWYpOAkk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=oFiVEVdb/xhSQ8KVEpComzU+r9ZVHO7tJsC71kjAQYoW6uJSddykOhJf75luI0nuv4EzLrZ416zZdZWhqqR0Ykn1ew3/FHBabzwRo6rTCLumRjZoGp41mZF89a8gVx8k8EzuVyUdpsegoJUE3EnV313QgzmOIkirrO0X8g0QnT8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk; spf=none smtp.mailfrom=armlinux.org.uk; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b=k2pFIpeN; arc=none smtp.client-ip=78.32.30.218 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="k2pFIpeN" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=uxn7PT+EAVFsbAjdQ2z3LbyFBgdM3inwgwbxduT95vI=; b=k2pFIpeNykpDXUpgGP6rmLNoV1 v/gsW08BVVUZfDPnDaCOYq/EPmKDFUni7x5/8twmANTmNfp5sQYO6M5iMkWl7C/Yj8eByFi0NSjP5 +pKn3gZs8uXX5sMu1Rwbj/XeNHpvtcP2iheVMIB9c8X8dDZWr122N2kazWTQ16RAvx+Ca1sHX+TFH ZtTLGhonByGtkYC2q3cf/86RHDlQDw9Ts/EgBNsL7k3mrWZZKvQpqmnPtBKewzJQHfSco39iq1brj m7SiZUcp6mag/2vpZ39mmJo8N3iPN8A5fDIP7p9oxcTGE7fua+tmzCqrAI/TrTSDeYeaqTt9EuUlm zRqHERBQ==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:51328) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1x3qkT-00000000835-1isj; Tue, 08 Sep 2026 09:00:09 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.98.2) (envelope-from ) id 1x3qkO-000000003sU-2C7X; Tue, 08 Sep 2026 09:00:04 +0100 Date: Tue, 8 Sep 2026 09:00:04 +0100 From: Russell King To: Sebastian Andrzej Siewior Cc: Steven Rostedt , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, linux-perf-users@vger.kernel.org, loongarch@lists.linux.dev, Mark Rutland , Ian Rogers , Peter Zijlstra , "Luis Claudio R. Goncalves" , Catalin Marinas , James Clark , Huacai Chen , Adrian Hunter , Oleg Nesterov , Alexander Shishkin , Ingo Molnar , Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim , Waiman Long , WANG Xuerui , Will Deacon , Clark Williams Subject: Re: [PATCH v2] ARM, ARM64, LONGARCH: Delay HW BP notification to task_work() Message-ID: References: <20260814085118.OPEA_Ssn@linutronix.de> <20260903160710.vVf4gEL2@linutronix.de> <20260903133146.07095885@gandalf.local.home> <20260904155404.ESPFg3zi@linutronix.de> <20260908075455.OffmMhrB@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260908075455.OffmMhrB@linutronix.de> Sender: "Russell King,,," On Tue, Sep 08, 2026 at 09:54:55AM +0200, Sebastian Andrzej Siewior wrote: > On 2026-09-07 15:46:09 [+0100], Russell King wrote: > > On Fri, Sep 04, 2026 at 05:54:04PM +0200, Sebastian Andrzej Siewior wrote: > > > On 2026-09-03 13:31:46 [-0400], Steven Rostedt wrote: > > > > On Thu, 3 Sep 2026 17:47:24 +0100 > > > > Russell King wrote: > > > > > > > > > What do you expect to happen with this? Which arch maintainer should > > > > > apply this patch that affects three different independently maintained > > > > > architectures? > > > > > > Well, if you as the ARM person are fine with ARM part, an ACK would be > > > appreciated. If you have something to object, it would be nice to let me > > > know so I can adjust accordingly. > > > > First, I only just looked at the email - you may have noticed I'm not > > very active with the kernel anymore, as I'm a full-time carer at the > > moment. > > > > Second, I'm not fine with the patch as-is, because it's not clear how > > it could be merged in its current form. It would be inappropriate to > > give an Ack, because an Ack means I'm fine with it. I'm not. > > > > Third, I haven't actually reviewed the patch itself (see first point). > > > > Looking deeper now, I see nothing in the linked report, nor in your > > write-up that identifies what is responsible for the context being > > inappropriate to deliver the SIGTRAP. See the first point - I'm not > > The linked report shows a backtrace by "BUG: sleeping function" > originating from el0_breakpt() -> perf_bp_event() following by sending a > signal force_sig_fault() followed by rt_spin_lock() and > __might_resched(). It also contains a reproducer. > > The first sentence has the part > | The hardware event is > | delivered with disabled interrupts and perf intrastrucure expects > | disabled interrupts while the overflow callback is invoked. *Where* are interrupts disabled? > > This is what happens, followed by > > | The callback then sends a SIGTRAP signal for which it acquires > | sighand_struct::siglock, a spinlock_t which becomes a sleeping lock and > | must not be acquired in atomic context. > > This is not really specific to PREEMPT_RT as we enforce to not allow > raw_spinlock_t -> spinlock_t on !PREEMPT_RT via lockdep, too. > > > able to read lots of code to work that out, and presumably you've > > already done that ground work to come up with a fix. This is *vital* > > information when someone looks back at why this change was made as > > it helps to understand how the problem occurs. This is, after all, > > the whole point of commit messages - to help people look back and > > understand why a change was made. The "what the changes are" part > > is already covered by the patch showing what the changes were. It's > > the stuff that *isn't* in the patch that needs to be in the commit > > message. > > > > So... don't describe the code changes in a commit message. > > I think both parts (describing the issue and the change) are part of the > commit message. > > > So no, an Ack is not appropriate. > > Sebastian > -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!