On Fri, Sep 13, 2019 at 10:35 PM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, 13 Sep 2019, syzbot wrote: > > > syzbot has found a reproducer for the following crash on: > > > > HEAD commit: f0df5c1b usb-fuzzer: main usb gadget fuzzer driver > > git tree: https://github.com/google/kasan.git usb-fuzzer > > console output: https://syzkaller.appspot.com/x/log.txt?x=1146550d600000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5 > > dashboard link: https://syzkaller.appspot.com/bug?extid=b24d736f18a1541ad550 > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11203fa5600000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=162cd335600000 > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+b24d736f18a1541ad550@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > yurex 3-1:0.101: yurex_interrupt - unknown status received: -71 > > yurex 5-1:0.101: yurex_interrupt - unknown status received: -71 > > yurex 6-1:0.101: yurex_interrupt - unknown status received: -71 > > rcu: INFO: rcu_sched self-detected stall on CPU > > Andrey: > > This problem may be a result of overloading dummy_timer. The kernel > config you are using has CONFIG_HZ=100, but dummy-hcd needs > CONFIG_HZ=1000 (see the comment on line 1789). That is, lower values > of HZ will occasionally lead to trouble, and this may be an example. > > Can you change the config value for HZ and see if the bug still > reproduces? Hi Alan, I've tried running the reproducer with CONFIG_HZ=1000 and still got the same stall message. It's accompanied by countless "yurex 6-1:0.101: yurex_interrupt - unknown status received: -71" messages, so I believe this is an issue in the yurex driver. Why does dumy_hcd require CONFIG_HZ=1000? The comment doesn't really explain the reason. Thanks!
