From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 39C32C433F5 for ; Wed, 22 Dec 2021 18:19:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344556AbhLVSTO (ORCPT ); Wed, 22 Dec 2021 13:19:14 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:60172 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233546AbhLVSTO (ORCPT ); Wed, 22 Dec 2021 13:19:14 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id C784361BDF; Wed, 22 Dec 2021 18:19:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96714C36AE5; Wed, 22 Dec 2021 18:19:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1640197153; bh=dfqJKK811rMxuyT1U4YfZICZU/vmelBIfBL2C0++wKc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=m2p0xptdbVkaUdxXMr0HQ8gpS1rpJKIOWIL7GLw8fcnhDxXd1ZcUgTfBMsFtHZHXp DD1KzVInXn7w+qvy99ukdgq3FB23iVN9Z5pENZIi+w+hSiDVsMBSDL/n4YfsZ6uAFY POCL4VZpp6yv/qSOx02PC5Iw9AQ8CNsSqlQD7skgw0rqQmg8ppT5yJX9Q2ALPFSfPU Wb5eih0h+E95JzfOlPURzlhbvmB2kIywy3vWtDpcJhxJK/HZDYJ6U3zUELijn0kMlz dRaTva03/8+rVqu5vyz8GQX12e7X+/rOzNZc5Uh6V3c/QLBjsWXQR7VR+gcP4ueBYP VJXdgK8qrmMWg== Date: Wed, 22 Dec 2021 11:19:07 -0700 From: Nathan Chancellor To: "Eric W. Biederman" Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Linus Torvalds , Alexey Gladkov , Kyle Huey , Oleg Nesterov , Kees Cook , Al Viro , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Alexander Gordeev , Martin Schwidefsky Subject: Re: [PATCH 09/10] kthread: Ensure struct kthread is present for all kthreads Message-ID: References: <87a6ha4zsd.fsf@email.froward.int.ebiederm.org> <20211208202532.16409-9-ebiederm@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211208202532.16409-9-ebiederm@xmission.com> Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org Hi Eric, On Wed, Dec 08, 2021 at 02:25:31PM -0600, Eric W. Biederman wrote: > Today the rules are a bit iffy and arbitrary about which kernel > threads have struct kthread present. Both idle threads and thread > started with create_kthread want struct kthread present so that is > effectively all kernel threads. Make the rule that if PF_KTHREAD > and the task is running then struct kthread is present. > > This will allow the kernel thread code to using tsk->exit_code > with different semantics from ordinary processes. > > To make ensure that struct kthread is present for all > kernel threads move it's allocation into copy_process. > > Add a deallocation of struct kthread in exec for processes > that were kernel threads. > > Move the allocation of struct kthread for the initial thread > earlier so that it is not repeated for each additional idle > thread. > > Move the initialization of struct kthread into set_kthread_struct > so that the structure is always and reliably initailized. > > Clear set_child_tid in free_kthread_struct to ensure the kthread > struct is reliably freed during exec. The function > free_kthread_struct does not need to clear vfork_done during exec as > exec_mm_release called from exec_mmap has already cleared vfork_done. > > Signed-off-by: "Eric W. Biederman" This patch as commit 40966e316f86 ("kthread: Ensure struct kthread is present for all kthreads") in -next causes an ARCH=arm multi_v5_defconfig kernel to fail to boot in QEMU. I had to apply commit 6692c98c7df5 ("fork: Stop protecting back_fork_cleanup_cgroup_lock with CONFIG_NUMA") to get it to build and I applied commit dd621ee0cf8e ("kthread: Warn about failed allocations for the init kthread") to avoid the known runtime warning. $ make -skj"$(nproc)" ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- distclean multi_v5_defconfig all $ qemu-system-arm \ -initrd rootfs.cpio \ -append earlycon \ -machine palmetto-bmc \ -no-reboot \ -dtb arch/arm/boot/dts/aspeed-bmc-opp-palmetto.dtb \ -display none \ -kernel arch/arm/boot/zImage \ -m 512m \ -nodefaults \ -serial mon:stdio qemu-system-arm: warning: nic ftgmac100.0 has no peer qemu-system-arm: warning: nic ftgmac100.1 has no peer Booting Linux on physical CPU 0x0 Linux version 5.16.0-rc1-00016-g40966e316f86-dirty (nathan@archlinux-ax161) (arm-linux-gnueabi-gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2) #1 PREEMPT Wed Dec 22 18:08:53 UTC 2021 CPU: ARM926EJ-S [41069265] revision 5 (ARMv5TEJ), cr=00093177 CPU: VIVT data cache, VIVT instruction cache OF: fdt: Machine model: Palmetto BMC earlycon: ns16550a0 at MMIO 0x1e784000 (options '') printk: bootconsole [ns16550a0] enabled Memory policy: Data cache writethrough cma: Reserved 16 MiB at 0x5b000000 Zone ranges: DMA [mem 0x0000000040000000-0x000000005edfffff] Normal empty HighMem [mem 0x000000005ee00000-0x000000005fffffff] Movable zone start for each node Early memory node ranges node 0: [mem 0x0000000040000000-0x000000005bffffff] node 0: [mem 0x000000005c000000-0x000000005dffffff] node 0: [mem 0x000000005e000000-0x000000005edfffff] node 0: [mem 0x000000005ee00000-0x000000005fffffff] Initmem setup node 0 [mem 0x0000000040000000-0x000000005fffffff] Built 1 zonelists, mobility grouping on. Total pages: 130084 Kernel command line: earlycon Dentry cache hash table entries: 65536 (order: 6, 262144 bytes, linear) Inode-cache hash table entries: 32768 (order: 5, 131072 bytes, linear) mem auto-init: stack:off, heap alloc:off, heap free:off Memory: 433140K/524288K available (9628K kernel code, 2019K rwdata, 2368K rodata, 340K init, 661K bss, 74764K reserved, 16384K cma-reserved, 0K highmem) SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1 rcu: Preemptible hierarchical RCU implementation. rcu: RCU event tracing is enabled. Trampoline variant of Tasks RCU enabled. rcu: RCU calculated value of scheduler-enlistment delay is 10 jiffies. NR_IRQS: 16, nr_irqs: 16, preallocated irqs: 16 i2c controller registered, irq 16 random: get_random_bytes called from start_kernel+0x408/0x624 with crng_init=0 clocksource: FTTMR010-TIMER2: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 79635851949 ns sched_clock: 32 bits at 24MHz, resolution 41ns, wraps every 89478484971ns Switching to timer-based delay loop, resolution 41ns Console: colour dummy device 80x30 printk: console [tty0] enabled printk: bootconsole [ns16550a0] disabled After that, it just hangs. The rootfs is available at https://github.com/ClangBuiltLinux/boot-utils in the images/arm folder. If there is any more information that I can provide or changes to test, please let me know. Cheers, Nathan