Messages in this thread | | | Date | Tue, 16 Oct 2018 15:24:06 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: INFO: rcu detected stall in do_idle |
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On Sat, 13 Oct 2018, syzbot wrote: > syzbot found the following crash on: > > HEAD commit: 6b3944e42e2e afs: Fix cell proc list > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1545a479400000 > kernel config: https://syzkaller.appspot.com/x/.config?x=88e9a8a39dc0be2d > dashboard link: https://syzkaller.appspot.com/bug?extid=385468161961cee80c31 > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14825d5e400000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=122cc531400000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+385468161961cee80c31@syzkaller.appspotmail.com > > sshd (5193) used greatest stack depth: 15496 bytes left > sched: DL replenish lagged too much > hrtimer: interrupt took 417330 ns > rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
It does reproduce here but with a kworker stall. Looking at the reproducer:
*(uint32_t*)0x20000000 = 0; *(uint32_t*)0x20000004 = 6; *(uint64_t*)0x20000008 = 0; *(uint32_t*)0x20000010 = 0; *(uint32_t*)0x20000014 = 0; *(uint64_t*)0x20000018 = 0x9917; *(uint64_t*)0x20000020 = 0xffff; *(uint64_t*)0x20000028 = 0; syscall(__NR_sched_setattr, 0, 0x20000000, 0);
which means:
struct sched_attr { .size = 0, .policy = 6, .flags = 0, .nice = 0, .priority = 0, .deadline = 0x9917, .runtime = 0xffff, .period = 0, }
policy 6 is SCHED_DEADLINE
That makes the thread hog the CPU and prevents all kind of stuff to run.
Peter, is that expected behaviour?
Thanks,
tglx
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