Re: [PATCH v4] rcu-tasks: Make rude RCU-Tasks work well with CPU hotplug

From: Paul E. McKenney
Date: Wed Dec 21 2022 - 14:33:34 EST

On Mon, Dec 19, 2022 at 02:21:01AM +0000, Zhang, Qiang1 wrote:
> >Greeting,
> >FYI, we noticed WARNING:at_kernel/rcu/rcutorture.c:#rcu_torture_fwd_prog_cr[rcutorture] due to commit (built with gcc-11):
> >
> >commit: 572a17843591d3c03ad891492939a06833fdd17d ("[PATCH v4] rcu-tasks: Make rude RCU-Tasks work well with CPU hotplug")
> >url: https://github.com/intel-lab-lkp/linux/commits/Zqiang/rcu-tasks-Make-rude-RCU-Tasks-work-well-with-CPU-hotplug/20221201-074127
> >base: https://git.kernel.org/cgit/linux/kernel/git/paulmck/linux-rcu.git dev
> >patch link: https://lore.kernel.org/all/20221130234533.1983769-1-qiang1.zhang@xxxxxxxxx/
> >patch subject: [PATCH v4] rcu-tasks: Make rude RCU-Tasks work well with CPU hotplug
> >
> >in testcase: rcutorture
> >version:
> >with following parameters:
> >
> > runtime: 300s
> > test: cpuhotplug
> > torture_type: tasks-rude
> >
> >test-description: rcutorture is rcutorture kernel module load/unload test.
> >test-url: https://www.kernel.org/doc/Documentation/RCU/torture.txt
> >
> >on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 8G
> >
> >caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> >
> >
> >[ 106.051532][ T583] rcu_torture_fwd_prog: Starting forward-progress test 0
> >[ 106.052085][ T583] rcu_torture_fwd_prog_cr: Starting forward-progress test 0
> >[ 133.611262][ T583] rcu_torture_fwd_prog_cr: Waiting for CBs: rcu_barrier_tasks_rude+0x0/0x10() 0
> >[ 146.800051][ T583] ------------[ cut here ]------------
> >[ 146.800411][ T583] WARNING: CPU: 1 PID: 583 at kernel/rcu/rcutorture.c:2806 rcu_torture_fwd_prog_cr+0x22c/0x2a7 [rcutorture]
> >[ 146.801075][ T583] Modules linked in: rcutorture torture ipmi_msghandler crc32c_intel serio_raw processor fuse
> >[ 146.801894][ T583] CPU: 1 PID: 583 Comm: rcu_torture_fwd Not tainted 6.1.0-rc1-00180-g572a17843591 #1 0cc09f902db70bae111a0c12c137296733dde4a9
> >[ 146.802916][ T583] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-debian-1.16.0-5 04/01/2014
> >[ 146.803693][ T583] EIP: rcu_torture_fwd_prog_cr+0x22c/0x2a7 [rcutorture]
> >[ 146.804177][ T583] Code: 89 d8 e8 fc c5 ff ff e8 67 49 03 00 83 c4 10 84 c0 75 79 a0 96 c6 10 ef 84 c0 75 70 e8 c8 ee ff ff 84 c0 75 67 83 fe 63 7f 02 <0f> 0b 8b 45 f0 8b 15 40 25 8a c2 ff 75 e8 ff 75 e0 01 f8 2b 45 dc
> >[ 146.805599][ T583] EAX: 00000000 EBX: ecee3800 ECX: 00000000 EDX: 00000000
> >[ 146.805992][ T583] ESI: 00000000 EDI: 0000c350 EBP: ed9d5f64 ESP: ed9d5f40
> >[ 146.806491][ T583] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00010293
> >[ 146.807010][ T583] CR0: 80050033 CR2: 08082ff0 CR3: 2daaf000 CR4: 000406d0
> >[ 146.807484][ T583] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> >[ 146.808031][ T583] DR6: fffe0ff0 DR7: 00000400
> >[ 146.808384][ T583] Call Trace:
> >[ 146.808634][ T583] rcu_torture_fwd_prog.cold+0x3b/0xee [rcutorture 6754ed9afe4685f50ef7fade6309181c73794538]
> >[ 146.809348][ T583] kthread+0xc8/0xf0
> >[ 146.809635][ T583] ? rcu_torture_fwd_prog_cbfree+0x80/0x80 [rcutorture 6754ed9afe4685f50ef7fade6309181c73794538]
> >[ 146.810347][ T583] ? kthread_complete_and_exit+0x20/0x20
> >[ 146.810734][ T583] ret_from_fork+0x1c/0x28
> >[ 146.811075][ T583] irq event stamp: 205883
> >[ 146.811400][ T583] hardirqs last enabled at (205891): [<c114bb06>] __up_console_sem+0x66/0x80
> >[ 146.811960][ T583] hardirqs last disabled at (205898): [<c114baed>] __up_console_sem+0x4d/0x80
> >[ 146.812583][ T583] softirqs last enabled at (205880): [<c1ecb40b>] __do_softirq+0x2bb/0x440
> >[ 146.813079][ T583] softirqs last disabled at (205871): [<c10845f0>] call_on_stack+0x40/0x50
> >[ 146.813567][ T583] ---[ end trace 0000000000000000 ]---
> >[ 146.813926][ T583] rcu_torture_fwd_prog_cr Duration 2411 barrier: 3960 pending 50000 n_launders: 0 n_launders_sa: 0 n_max_gps: 0 n_max_cbs: 50000 cver 1 gps 0
> >[ 147.914266][ T583] rcu_torture_fwd_cb_hist: Callback-invocation histogram 0 (duration 6702 jiffies): 1s/10: 0:0 2s/10:
> >[ 149.453780][ T557] ------------[ cut here ]------------
> >[ 149.454322][ T557] rcu_torture_writer: rtort_pipe_count: 4
> >[ 149.454817][ T557] WARNING: CPU: 1 PID: 557 at kernel/rcu/rcutorture.c:1583 rcu_torture_writer+0x71d/0xc80 [rcutorture]
>
>
> This is not a bug. this is caused by grace period taking too long time, the previous callback
> has not been completed. from the dmesg, can be found that the cpuhotplug test is being
> performed periodically, this may cause the rude RCU-Tasks grace period to take more time,
> due to we need to acquire the cpus_read_lock, and the CPU0 always bootup failed, that is to
> say, only one CPU of your system is online at this time.

Onlining of a CPU failing with EIO is a new one on me. Especially
persistent failure.

Thanx, Paul

> Thanks
> Zqiang
>
> >[ 149.455687][ T557] Modules linked in: rcutorture torture ipmi_msghandler crc32c_intel serio_raw processor fuse
> >[ 149.456490][ T557] CPU: 1 PID: 557 Comm: rcu_torture_wri Tainted: G W 6.1.0-rc1-00180-g572a17843591 #1 0cc09f902db70bae111a0c12c137296733dde4a9
> >[ 149.457660][ T557] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-debian-1.16.0-5 04/01/2014
> >[ 149.458484][ T557] EIP: rcu_torture_writer+0x71d/0xc80 [rcutorture]
> >[ 149.458990][ T557] Code: 05 00 00 8d 43 f4 39 c6 74 c3 e8 0e a0 0b d2 83 ff 63 0f 87 3d 05 00 00 ff 73 fc 68 88 a0 10 ef 68 f4 9a 10 ef e8 10 01 d2 d2 <0f> 0b a1 30 c6 10 ef 83 c4 0c 85 c0 75 95 b8 01 00 00 00 87 05 30
> >[ 149.460472][ T557] EAX: 00000027 EBX: ef10d630 ECX: e49c0f28 EDX: e49c0f24
> >[ 149.461022][ T557] ESI: ef10d694 EDI: 0000004f EBP: ece35f8c ESP: ece35f18
> >[ 149.461539][ T557] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00010292
> >[ 149.462101][ T557] CR0: 80050033 CR2: 08082ff0 CR3: 2daaf000 CR4: 000406d0
> >[ 149.462642][ T557] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> >[ 149.463172][ T557] DR6: fffe0ff0 DR7: 00000400
> >[ 149.463526][ T557] Call Trace:
> >[ 149.463795][ T557] ? lockdep_hardirqs_on_prepare+0xa4/0x160
> >[ 149.464333][ T557] ? _raw_spin_unlock_irqrestore+0x45/0x60
> >[ 149.464795][ T557] ? trace_hardirqs_on+0x35/0xe0
> >[ 149.465191][ T557] kthread+0xc8/0xf0
> >[ 149.465506][ T557] ? rcu_torture_pipe_update+0x130/0x130 [rcutorture 6754ed9afe4685f50ef7fade6309181c73794538]
> >[ 149.466327][ T557] ? kthread_complete_and_exit+0x20/0x20
> >[ 149.466771][ T557] ret_from_fork+0x1c/0x28
> >[ 149.467136][ T557] irq event stamp: 45753
> >[ 149.467457][ T557] hardirqs last enabled at (45761): [<c114bb06>] __up_console_sem+0x66/0x80
> >[ 149.468145][ T557] hardirqs last disabled at (45770): [<c114baed>] __up_console_sem+0x4d/0x80
> >[ 149.468803][ T557] softirqs last enabled at (41056): [<ef1037a0>] rcu_torture_pipe_update+0xe0/0x130 [rcutorture]
> >[ 149.469602][ T557] softirqs last disabled at (41054): [<ef10377c>] rcu_torture_pipe_update+0xbc/0x130 [rcutorture]
> >[ 149.470401][ T557] ---[ end trace 0000000000000000 ]---
>