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Date: Fri, 7 Oct 2022 14:09:11 -0400
From: Waiman Long <longman@...hat.com>
To: kernel test robot <yujie.liu@...el.com>
Cc: lkp@...ts.01.org, lkp@...el.com, linux-kernel@...r.kernel.org,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Valentin Schneider <vschneid@...hat.com>,
Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
Johannes Weiner <hannes@...xchg.org>,
Will Deacon <will@...nel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Lai Jiangshan <jiangshanlai@...il.com>
Subject: Re: [sched] 3cf68f7aae:
WARNING:at_kernel/rcu/update.c:#rcutorture_sched_setaffinity
On 9/25/22 22:51, kernel test robot wrote:
> Hi Waiman,
>
> While this report is for v9 patch, we found that the issue also happens
> on v10 patch, so we send this report FYI. Thanks.
>
> Greeting,
>
> FYI, we noticed the following commit (built with gcc-11):
>
> commit: 3cf68f7aaecb7f1482f3183a5925641632658667 ("[PATCH v9 2/7] sched: Use user_cpus_ptr for saving user provided cpumask in sched_setaffinity()")
> url: https://github.com/intel-lab-lkp/linux/commits/Waiman-Long/sched-Persistent-user-requested-affinity/20220917-023345
> base: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git 6879c2d3b96039ff1668b4328a4d0dd3ea952cff
> patch link: https://lore.kernel.org/lkml/20220916183217.1172225-3-longman@redhat.com
>
> in testcase: rcutorture
> version:
> with following parameters:
>
> runtime: 300s
> test: cpuhotplug
> torture_type: trivial
>
> test-description: rcutorture is rcutorture kernel module load/unload test.
> test-url: https://www.kernel.org/doc/Documentation/RCU/torture.txt
> dl_task_check_affinity
>
> on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
>
> caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
>
>
> [ 95.904059][ T543] ------------[ cut here ]------------
> [ 95.904506][ T543] rcutorture_sched_setaffinity: sched_setaffinity() returned -22
> [ 95.905105][ T543] WARNING: CPU: 0 PID: 543 at kernel/rcu/update.c:495 rcutorture_sched_setaffinity+0x45/0x50
> [ 95.905843][ T543] Modules linked in: rcutorture torture
> [ 95.906279][ T543] CPU: 0 PID: 543 Comm: rcu_torture_fak Tainted: G W 6.0.0-rc5-00091-g3cf68f7aaecb #1
> [ 95.907111][ T543] EIP: rcutorture_sched_setaffinity+0x45/0x50
> [ 95.907640][ T543] Code: 94 d0 82 00 75 ee 89 44 24 08 b9 88 5e f9 81 b2 01 89 4c 24 04 c7 04 24 00 d9 5f 82 88 15 8a 94 d0 82 89 45 fc e8 db 4d dc 00 <0f> 0b 8b 45 fc 89 ec 5d c3 66 90 55 31 c0 80 3d dc 65 65 83 00 89
> [ 95.909113][ T543] EAX: 0000003e EBX: 00000000 ECX: e756ff14 EDX: 00001794
> [ 95.909666][ T543] ESI: ee381d00 EDI: 00000002 EBP: ed37ff44 ESP: ed37ff34
> [ 95.910203][ T543] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00010282
> [ 95.910816][ T543] CR0: 80050033 CR2: 77d40bb0 CR3: 06a9a000 CR4: 000406b0
> [ 95.911357][ T543] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> [ 95.911895][ T543] DR6: fffe0ff0 DR7: 00000400
> [ 95.912255][ T543] Call Trace:
> [ 95.912529][ T543] synchronize_rcu_trivial+0x57/0xf0 [rcutorture]
> [ 95.913034][ T543] rcu_torture_fakewriter+0x108/0x280 [rcutorture]
> [ 95.913532][ T543] kthread+0xcd/0xf0
> [ 95.913839][ T543] ? rcu_read_unlock+0x60/0x60 [rcutorture]
> [ 95.914311][ T543] ? kthread_complete_and_exit+0x20/0x20
> [ 95.914734][ T543] ret_from_fork+0x19/0x24
> [ 95.915065][ T543] irq event stamp: 66091
> [ 95.915386][ T543] hardirqs last enabled at (66099): [<810d5f79>] __up_console_sem+0x69/0x80
> [ 95.916046][ T543] hardirqs last disabled at (66106): [<810d5f5d>] __up_console_sem+0x4d/0x80
> [ 95.916711][ T543] softirqs last enabled at (66072): [<81f8e014>] __do_softirq+0x284/0x4a3
> [ 95.917377][ T543] softirqs last disabled at (66063): [<8100b544>] do_softirq_own_stack+0x24/0x30
> [ 95.918043][ T543] ---[ end trace 0000000000000000 ]---
>
>
> If you fix the issue, kindly add following tag
> | Reported-by: kernel test robot <yujie.liu@...el.com>
> | Link: https://lore.kernel.org/r/202209260935.35aecc5a-yujie.liu@intel.com
>
>
> To reproduce:
>
> # build kernel
> cd linux
> cp config-6.0.0-rc5-00091-g3cf68f7aaecb .config
> make HOSTCC=gcc-11 CC=gcc-11 ARCH=i386 olddefconfig prepare modules_prepare bzImage modules
> make HOSTCC=gcc-11 CC=gcc-11 ARCH=i386 INSTALL_MOD_PATH=<mod-install-dir> modules_install
> cd <mod-install-dir>
> find lib/ | cpio -o -H newc --quiet | gzip > modules.cgz
>
>
> git clone https://github.com/intel/lkp-tests.git
> cd lkp-tests
> bin/lkp qemu -k <bzImage> -m modules.cgz job-script # job-script is attached in this email
>
> # if come across any failure that blocks the test,
> # please remove ~/.lkp and /lkp dir to run from a clean state.
>
>
The warning happens in the following code:
490 long rcutorture_sched_setaffinity(pid_t pid, const struct
cpumask *in_mask)
491 {
492 int ret;
493
494 ret = sched_setaffinity(pid, in_mask);
495 WARN_ONCE(ret, "%s: sched_setaffinity() returned %d\n",
__func__, ret);
496 return ret;
497 }
792 static void synchronize_rcu_trivial(void)
793 {
794 int cpu;
795
796 for_each_online_cpu(cpu) {
797 rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu));
798 WARN_ON_ONCE(raw_smp_processor_id() != cpu);
799 }
800 }
The original sched_setaffinity() code hide the failure due to racing in
cpuset's cpus_allowed change. So it won't fail even if the new cpu being
set is different from the mask given by the caller. The patch changes
the code that will return a failure code instead. In this particular
failure, the calling synchronize_rcu_trivial() should have triggered its
WARN_ON_ONCE() check. Since this warning has been triggered before, it
won't show up a second time. As a result, you have two warnings instead
of one.
-Longman
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