lkml.org 
[lkml]   [2020]   [Nov]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH] kfence: Avoid stalling work queue task without allocations
    On Wed, 11 Nov 2020 at 16:01, Anders Roxell <anders.roxell@linaro.org> wrote:
    >
    > On Wed, 11 Nov 2020 at 09:29, Marco Elver <elver@google.com> wrote:
    > >
    > > On Wed, 11 Nov 2020 at 00:23, Anders Roxell <anders.roxell@linaro.org> wrote:
    > > [...]
    > > >
    > > > I gave them a spin on next-20201105 [1] and on next-20201110 [2].
    > > >
    > > > I eventually got to a prompt on next-20201105.
    > > > However, I got to this kernel panic on the next-20201110:
    > > >
    > > > [...]
    > > > [ 1514.089966][ T1] Testing event system initcall: OK
    > > > [ 1514.806232][ T1] Running tests on all trace events:
    > > > [ 1514.857835][ T1] Testing all events:
    > > > [ 1525.503262][ C0] hrtimer: interrupt took 10902600 ns
    > > > [ 1623.861452][ C0] BUG: workqueue lockup - pool cpus=0 node=0
    > > > flags=0x0 nice=0 stuck for 65s!
    > > > [...]
    > > > [ 7823.104349][ T28] Tainted: G W
    > > > 5.10.0-rc3-next-20201110-00008-g8dc06700529d #3
    > > > [ 7833.206491][ T28] "echo 0 >
    > > > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
    > > > [ 7840.750700][ T28] task:kworker/0:1 state:D stack:26640 pid:
    > > > 1872 ppid: 2 flags:0x00000428
    > > > [ 7875.642531][ T28] Workqueue: events toggle_allocation_gate
    > > > [ 7889.178334][ T28] Call trace:
    > > > [ 7897.066649][ T28] __switch_to+0x1cc/0x1e0
    > > > [ 7905.326856][ T28] 0xffff00000f7077b0
    > > > [ 7928.354644][ T28] INFO: lockdep is turned off.
    > > > [ 7934.022572][ T28] Kernel panic - not syncing: hung_task: blocked tasks
    > > > [ 7934.032039][ T28] CPU: 0 PID: 28 Comm: khungtaskd Tainted: G
    > > > W 5.10.0-rc3-next-20201110-00008-g8dc06700529d #3
    > > > [ 7934.045586][ T28] Hardware name: linux,dummy-virt (DT)
    > > > [ 7934.053677][ T28] Call trace:
    > > > [ 7934.060276][ T28] dump_backtrace+0x0/0x420
    > > > [ 7934.067635][ T28] show_stack+0x38/0xa0
    > > > [ 7934.091277][ T28] dump_stack+0x1d4/0x278
    > > > [ 7934.098878][ T28] panic+0x304/0x5d8
    > > > [ 7934.114923][ T28] check_hung_uninterruptible_tasks+0x5e4/0x640
    > > > [ 7934.123823][ T28] watchdog+0x138/0x160
    > > > [ 7934.131561][ T28] kthread+0x23c/0x260
    > > > [ 7934.138590][ T28] ret_from_fork+0x10/0x18
    > > > [ 7934.146631][ T28] Kernel Offset: disabled
    > > > [ 7934.153749][ T28] CPU features: 0x0240002,20002004
    > > > [ 7934.161476][ T28] Memory Limit: none
    > > > [ 7934.171272][ T28] ---[ end Kernel panic - not syncing: hung_task:
    > > > blocked tasks ]---
    > > >
    > > > Cheers,
    > > > Anders
    > > > [1] https://people.linaro.org/~anders.roxell/output-next-20201105-test.log
    > > > [2] https://people.linaro.org/~anders.roxell/output-next-20201110-test.log
    > >
    > > Thanks for testing. The fact that it passes on next-20201105 but not
    > > on 20201110 is strange. If you boot with KFENCE disabled (boot param
    > > kfence.sample_interval=0), does it boot?
    >
    > This is my qemu cmdline with kfence.sample_interval=0
    > $ qemu-system-aarch64 --enable-kvm -cpu cortex-a53 -kernel
    > Image-20201110-test -serial stdio -monitor none -nographic -m 2G -M
    > virt -fsdev local,id=root,path=/srv/kvm/tmp/stretch/arm64-test,security_model=none,writeout=immediate
    > -device virtio-rng-pci -device
    > virtio-9p-pci,fsdev=root,mount_tag=/dev/root -append "root=/dev/root
    > rootfstype=9p rootflags=trans=virtio console=ttyAMA0,38400n8
    > earlycon=pl011,0x9000000 initcall_debug softlockup_panic=0
    > security=none kpti=no kfence.sample_interval=0"
    >
    > This is the result, I managed to get to the prompt. see
    > https://people.linaro.org/~anders.roxell/output-next-20201110-test-2.log

    Hmm, you still have a ton of

    BUG: workqueue lockup - pool ...

    and other warnings in that log though that weren't there in
    next-20201105, so I do not trust the results until those are fixed. To
    me it looks like KFENCE's timer helps uncover a new problem, but
    trying to work around this new problem in KFENCE seems wrong for now.
    We need to understand why these "BUG: workqueue lockup" warnings are
    there. I Cc'd a bunch of folks in that other email that might be able
    to help.

    Thanks,
    -- Marco

    \
     
     \ /
      Last update: 2020-11-11 16:23    [W:4.074 / U:0.080 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site