Messages in this thread | | | Date | Tue, 16 Oct 2018 16:41:28 +0200 | From | Juri Lelli <> | Subject | Re: INFO: rcu detected stall in do_idle |
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On 16/10/18 16:03, Peter Zijlstra wrote: > On Tue, Oct 16, 2018 at 03:24:06PM +0200, Thomas Gleixner wrote: > > 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? > > Sorta, just like FIFO-99 while(1);. Except we should be rejecting the > above configuration, because of the rule: > > runtime <= deadline <= period > > Juri, where were we supposed to check that?
Not if period == 0.
https://elixir.bootlin.com/linux/latest/source/kernel/sched/deadline.c#L2632 https://elixir.bootlin.com/linux/latest/source/kernel/sched/deadline.c#L2515
Now, maybe we should be checking also against the default 95% cap?
Best,
- Juri
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