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 C71F93A1E8B for ; Fri, 16 Jan 2026 20:09:52 +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=1768594194; cv=none; b=kZXGMqN2coVSAhxj54NYxYf6rQNSqkICoKS2OFaJR5h7FdDFn+lQIZbdU1r8BqaQSn+VTFWsrCJyPdB0paHCKOTCthvkf24E0Ig04Bjkrp/N/DQHEGNH5ke13FI2K29/8LO6XHoEFYmwSgkySKVyLqWMt8/jUn5l/S0NYn9NmhE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768594194; c=relaxed/simple; bh=xhvEhgTxpzw8FKi/2iavt8ArNhknjWDqN9Co8r6sfuQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fSVdxOuIp1dAwL61Q0bV6hkjbOZGYQLN0JSHPaaB60SjzNvxj8rzomVr/lkZIFnPmZRbg+RKZnpP+RTa1O3j3vbTFyDpzh91qR4JHpasngABTybgM/bXaKqxhIJg+RfOcB19bLN3XfdRSFRozbtvWYt24bWqn68S4IfQbjrUTDY= 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=axjmhudE; 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="axjmhudE" 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=cWzXywP779e9MNfrlQWmWyODpNBngl6JXST0EKlobYM=; b=axjmhudEl0bQt4bj5rAVrApBTg DI0+lVIl1EAUP2gSmGYDY4Y1MKi+VHPgtJUk9dl+BQ34h6hjNeccuo8QW1h3iDF/3dMJQEMiHWQKX Uw8tufpEDzudOBqal/AmKOKA7RPI0/be0E5Zpi/KPrX5HHiee4s0trWKdto/gQTVy361Udc0VdJMP 6mZcpjic1cG2yrnS7wAkNxdDPIJp6R+R90yj42xA13vLLGayUMZ5vJFLDsM8Idery3GMvpo3JBMgS DRrgGVrMOxcV11eDaWaS7dWzI5l0SplKGiHOpya/2rIpuv87grWIgtyU2kdoyKs5njumcYw6DLOHH m95WfhrA==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:57758) 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 1vgq8g-000000002fs-44Dn; Fri, 16 Jan 2026 20:09:47 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.98.2) (envelope-from ) id 1vgq8d-000000003t0-3rSt; Fri, 16 Jan 2026 20:09:43 +0000 Date: Fri, 16 Jan 2026 20:09:43 +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 08:07:52PM +0000, Russell King (Oracle) wrote: > 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. Sorry for a third reply... yesterday I started at about 10am, finished at 2am last night chasing a different stmmac regression. Yea, if there was more time, then I could push all the patches I have, but I don't, and the above patches were generated back when we were discussing the issue last time. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!