Marc Zyngier <maz@xxxxxxxxxx> writes:
> On Sat, 1 Feb 2020 09:31:17 +0800
> Ming Lei <tom.leiming@xxxxxxxxx> wrote:
>> On Sat, Feb 1, 2020 at 2:02 AM John Garry <john.garry@xxxxxxxxxx> wrote:
>>
>> gic_set_affinity shouldn't have switched out, so looks like one gic
>> issue.
>
> Given that gic_set_affinity doesn't sleep, this looks pretty unlikely.
> And __irq_set_affinity() holds a spinlock with irq disabled, so I can't
> really explain how you'd get there. I've just booted a lockdep enabled
> v5.5 on my D05, moved SPIs around (because that's the only way to reach
> this code), and nothing caught fire.
>
> Either the stack trace isn't reliable (when I read things like
> "80d:00h:35m:42s" in the trace, I'm a bit suspicious), or CPU hotplug is
> doing something really funky here.
The hotplug code cannot end up in schedule either and it holds desc lock
as normal affinity setting. The other backtrace is more complete,
[ 728.741808] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:80d:00h:35m:42s]
[ 728.747895] rcu: 48-...0: (0 ticks this GP) idle=b3e/1/0x4000000000000000 softirq=5548/5548 fqs=2626
[ 728.757197] (detected by 63, t=5255 jiffies, g=40989, q=1890)
[ 728.763018] Task dump for CPU 48:
[ 728.766321] irqbalance R running task 0 1272 1 0x00000002
[ 728.773358] Call trace:
[ 728.775801] __switch_to+0xbc/0x218
[ 728.779283] gic_set_affinity+0x16c/0x1d8
[ 728.783282] irq_do_set_affinity+0x30/0xd0
[ 728.787365] irq_set_affinity_locked+0xc8/0xf0
[ 728.791796] __irq_set_affinity+0x4c/0x80
[ 728.795794] write_irq_affinity.isra.7+0x104/0x120
[ 728.800572] irq_affinity_proc_write+0x1c/0x28
[ 728.805008] proc_reg_write+0x78/0xb8
[ 728.808660] __vfs_write+0x18/0x38
[ 728.812050] vfs_write+0xb4/0x1e0
[ 728.815352] ksys_write+0x68/0xf8
[ 728.818655] __arm64_sys_write+0x18/0x20
[ 728.822567] el0_svc_common.constprop.2+0x64/0x160
[ 728.827345] el0_svc_handler+0x20/0x80
[ 728.831082] el0_sync_handler+0xe4/0x188
[ 728.834991] el0_sync+0x140/0x180
But the __switch_to() there definitely does not make any sense at all.
Thanks,
tglx
