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 4F77639A80D for ; Fri, 16 Jan 2026 20:08:00 +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=1768594082; cv=none; b=dp+DjG7n4LoYLjyrLc0XaH7KyvtscFFwOxzZ+YM5M65yvKUIIbU0p2jr8OQodwooFZ0X5vnAZL0rkiOF0QwUwoHBXEbnlQZiLaApPQPjWxoJc0sGKEbxkhoVrTiXNAUI4Fmq3ISraf5XOKoTeYeg+ujvLXN0PK+vCsYvxe08beo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768594082; c=relaxed/simple; bh=2jq1stjitaI0nTvWAgqxycAKxoY9ArOYtGHmxExYUWA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=AAP2IWRDnsMxT8zceRO6s9//H2uftDKK4Xz9AB57eLdigXXHLeljvran02OpaLdrBlv8mZx3JSO1zgFAnSTtKS4dVPpshP6VjY4hGnDCTfQb6WAQzKY4eK5ZooO0I2+qFbwRSTWIHxr0QEXPAG4AM5q1quCFdMj/KVpZhAH959U= 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=QglP77Js; 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="QglP77Js" 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=Ib6Pre9AmKy6Deo0H6hsuR4Gt6AAwQyo8gA6MlsNCkY=; b=QglP77Js6qujevNNS3mbM4CkX+ AEMTT8Nmnpo1KVZ9wjSZxrd1RGfh/6taL+va6bS5b6nvPh/i73q4B3jAwpDcFoZfGx0N27ZXnJJ12 0smF8bbpIOGVpoOh3JX25Bqm8XjFnnlKg1lSn4rywesI2gLhAmsSc+PcMGmugpmp4QZdjkCr9azg+ g0jBA7xGJ3iBq64LcCB3DUCdsIs72RgnOSH090EM4XnSf6Gs2/0kCckyrEkAOzoJRHsNjSj7F8OIZ n1RUhRZ3vnSiyU7MBSPQmfgARR5Q8mSPhMbDeHpBqvMlb0ikEO9S9Oluubw8QE4drnPUuefwCbeA2 HvLFHhHg==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:47356) 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 1vgq6t-000000002eY-3ff9; Fri, 16 Jan 2026 20:07:55 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.98.2) (envelope-from ) id 1vgq6q-000000003rz-0o2T; Fri, 16 Jan 2026 20:07:52 +0000 Date: Fri, 16 Jan 2026 20:07:51 +0000 From: "Russell King (Oracle)" To: Sebastian Andrzej Siewior Cc: linux-arm-kernel@lists.infradead.org, linux-rt-devel@lists.linux.dev, Arnd Bergmann , Linus Walleij , "Yadi.hu" , Bryan Brattlof Subject: Re: [PATCH v4 1/2] ARM: mm: fault: Enable interrupts before invoking __do_user_fault() Message-ID: References: <20260116170041.1059997-1-bigeasy@linutronix.de> <20260116170041.1059997-2-bigeasy@linutronix.de> <20260116181201.v-z31XJY@linutronix.de> Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Russell King (Oracle) On Fri, Jan 16, 2026 at 08:01:20PM +0000, Russell King (Oracle) wrote: > On Fri, Jan 16, 2026 at 07:12:01PM +0100, Sebastian Andrzej Siewior wrote: > > On 2026-01-16 17:33:48 [+0000], Russell King (Oracle) wrote: > > > On Fri, Jan 16, 2026 at 06:00:40PM +0100, Sebastian Andrzej Siewior wrote: > > > > From: "Yadi.hu" > > > > > > > > A page fault from userland for a kernel address originates from from > > > > do_sect_fault() (!LPAE) or do_page_fault() and ends in __do_user_fault() > > > > by sending a signal. > > > > > > > > Sending a signal requires to acquire sighand_struct::siglock which is a > > > > spinlock_t. On PREEMPT_RT spinlock_t becomes a sleeping spin lock which > > > > requires interrupts to be enabled. Since the calling context is user > > > > land, interrupts must have been enabled so it is fine to enable them in > > > > this case. > > > > > > > > Enable interrupts in do_kernel_address_page_fault() unconditional in the > > > > user_mode case(). > > > > Enable interrupts in do_sect_fault() if they were previously enabled. > > > > > > Do you need any of this? __do_user_fault() now calls > > > local_irq_enable() as almost the first thing it does. > > > > Different path(s): > > > > LPAE > > | BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 > > | in_atomic(): 0, irqs_disabled(): 128, non_block: 0, pid: 639, name: arm-segfault > > | preempt_count: 0, expected: 0 > > | RCU nest depth: 0, expected: 0 > > | CPU: 0 UID: 0 PID: 639 Comm: arm-segfault3 Tainted: G W 6.19.0-rc5-dirty #7 PREEMPT_RT > > | Tainted: [W]=WARN > > | Hardware name: QEMU QEMU Virtual Machine, BIOS unknown 02/02/2022 > > | Call trace: > > | unwind_backtrace from show_stack+0x18/0x1c > > | show_stack from dump_stack_lvl+0x34/0x44 > > | dump_stack_lvl from __might_resched+0x180/0x1c0 > > | __might_resched from rt_spin_lock+0x3c/0x1f0 > > | rt_spin_lock from force_sig_info_to_task+0x24/0x184 > > | force_sig_info_to_task from force_sig_fault+0x50/0x74 > > | force_sig_fault from do_kernel_address_page_fault+0xa8/0xb4 > > | do_kernel_address_page_fault from do_DataAbort+0x38/0xac > > | do_DataAbort from __dabt_usr+0x50/0x60 > > > > !LPAE > > | BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 > > | in_atomic(): 0, irqs_disabled(): 128, non_block: 0, pid: 622, name: arm-segfault > > | preempt_count: 0, expected: 0 > > | RCU nest depth: 0, expected: 0 > > | CPU: 0 UID: 0 PID: 622 Comm: arm-segfault Tainted: G W 6.19.0-rc5-dirty #8 PREEMPT_RT > > | Tainted: [W]=WARN > > | Hardware name: QEMU QEMU Virtual Machine, BIOS unknown 02/02/2022 > > | Call trace: > > | unwind_backtrace from show_stack+0x18/0x1c > > | show_stack from dump_stack_lvl+0x34/0x44 > > | dump_stack_lvl from __might_resched+0x180/0x1c0 > > | __might_resched from rt_spin_lock+0x3c/0x1f0 > > | rt_spin_lock from force_sig_info_to_task+0x24/0x184 > > | force_sig_info_to_task from force_sig_fault+0x50/0x74 > > | force_sig_fault from do_sect_fault+0x30/0x80 > > | do_sect_fault from do_DataAbort+0x44/0xb8 > > | do_DataAbort from __dabt_usr+0x50/0x60 > > Right, because I haven't pushed all the patches out. What was pushed out > was the basic set of fixes during the last merge window: > > fd2dee1c6e22 ARM: fix branch predictor hardening (fixes) > 7733bc7d299d ARM: fix hash_name() fault > 40b466db1dff ARM: allow __do_kernel_fault() to report execution of memory faults > dea20281ac88 ARM: group is_permission_fault() with is_translation_fault() > edb924a7211c ARM: 9464/1: fix input-only operand modification in load_unaligned_zeropad() > > which were sent out on the 8th December, but I still have these: > > 1055c9d604f9 ARM: provide individual is_translation_fault() and is_permission_fault() > 47ce12a37f82 ARM: move FSR fault status definitions before fsr_fs() > eefbf2e97ad5 ARM: use BIT() and GENMASK() for fault status register fields > 5f1e55bed37f ARM: move is_permission_fault() and is_translation_fault() to fault.h > ad1c1212ae15 ARM: move vmalloc() lazy-page table population > 92442d814d99 ARM: ensure interrupts are enabled in __do_user_fault() > > and, because they weren't fixes, it would've been inappropriate to > post these. However, I was on vacation from the 11th December through > to the 2nd January, had the madness of the huge email mountain, and > been working on stmmac and internal work issues since, I've not had any > time to look at anything else. > > However, these changes will negate the need for your patch 1. Oh, and, as I've said on netdev recently, I have lots of patches. I don't have time to push all patches all the time. Those that I think are the highest priority get the attention - so if something goes quiet, the patches don't get progressed (because something else has taken over.) I haven't published these yet to my external git tree because they're currently on top of my raw private "development" branch containing... $ git lg origin..rmk | wc -l 473 many of those behind those I mentioned above. At some point I need to move them to their own separate branch, or to the "misc" branch after sending them to the mailing list... but the latter means spending time writing a covering message summarising the changes, and the key thing is "time". I've wasted almost all of today running a bisect for a stmmac issue that takes out my _entire_ network at home. It's wasted because what I thought was a good commit turns out, on re-testing, to have been bad, and right now I have no idea what a good commit is, and whether that even exists before the platform support was merged. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!