On Tue, Jan 01, 2019 at 12:44:35AM -0500, Qian Cai wrote:
> Running some mmap() workloads to put the system on low memory situation with
> swapping and OOM, and then it trigger this BUG(),
>
> void __noreturn do_task_dead(void)
> {
> /* Causes final put_task_struct in finish_task_switch(): */
> set_special_state(TASK_DEAD);
>
> /* Tell freezer to ignore us: */
> current->flags |= PF_NOFREEZE;
>
> __schedule(false);
> BUG();
>
> /* Avoid "noreturn function does return" - but don't continue if BUG()
> is a NOP: */
> for (;;)
> cpu_relax();
> }
This would mean that we somehow loose the TASK_DEAD state before hitting
schedule(), but that is something that should be avoided by
set_special_state(), which is supposed to serialize against concurrent
wake-ups.
Also see commit: b5bf9a90bbeb ("sched/core: Introduce set_special_state()")
How readily does this reproduce?
