Re: [PATCH] BUG(): sched.c: Line 944

Ingo Molnar
2002-09-17T15:41:22Z

On Tue, 17 Sep 2002, Linus Torvalds wrote:

> void schedule(void)
> {
> BUG_ON(in_atomic());
> BUG_ON(current->state & TASK_ZOMBIE);
> do_schedule();
> }
>
> void exit_schedule(void)
> {
> BUG_ON(!(current->state & TASK_ZOMBIE));
> do_schedule();
> }

i'd rather do it the other way around - ie. do a:

if (unlikely(current->state == TASK_ZOMBIE)) {
... exit checks ...
} else {
... normal checks ...
}

this test is cheaper than a function call. I'd say the ZOMBIE check alone
is not significant enough to introduce a function split in the hotpath.
This check is also easier to remove later on.

TASK_ZOMBIE is only ever allowed to be set for exiting tasks. [and if
TASK_ZOMBIE handling is broken then it will trigger the normal atomic
tests so it's not like we are silently ignoring those errors.]

Ingo