On Thu, Sep 27, 2018 at 7:50 PM, Cong Wang <xiyou.wangc...@gmail.com> wrote: > On Thu, Sep 27, 2018 at 1:11 AM Dmitry Vyukov <dvyu...@google.com> wrote: >> >> Would a stack trace for call_rcu be helpful here? I have this idea for >> a long time, but never get around to implementing it: >> https://bugzilla.kernel.org/show_bug.cgi?id=198437 > > Yes. Generally speaking, showing backtrace of call_rcu() > or schedule_work(0 etc. is very helpful, we are more interested > in who calls call_rcu() than what that RCU callback does. > > BTW, yesterday I asked syzbot to test this: > https://github.com/congwang/linux/commit/b7815584cf1c0bbb79e8f6fe3e4b66ba10375560 > I still don't get any result.
I see that test job. It's in some dead loop, now trying to run for 37'th time. I've just pushed a fix a bug that could have caused it (fuzzing the fuzzer, we should go deeper!): https://github.com/google/syzkaller/commit/98b28ead6ceaf22064b9715cc1950848d2bdef0b If it won't help, I will take a look tomorrow. > For this specific bug, we should hold a refcnt in dev->qdisc, I don't > even see how call_rcu() could be invoked, unless of course we mess > up with qdisc refcnt.
