Re: [linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch

Andrea Arcangeli
2004-07-13T22:39:30Z

On Tue, Jul 13, 2004 at 03:25:32PM -0700, Andrew Morton wrote:
> local_irq_disable();
> <fiddle with per-cpu stuff>
> function_which_calls_cond_resched();
> <fiddle with per-cpu stuff>
> local_irq_enable();
>
> then we want might_sleep() to warn about the bug.

might_sleep currently _doesn't_ warn about any bug in the above case I
quoted.

the kmalloc example is trapped instead.

>From my part I don't like anybody to call schedule with irq disabled
(and I would definitely put a debug check in schedule() for that, guess
how I found about the missing sti in entry.S btw). But if you are ok
with people calling schedule with irq disabled then I cannot put a check
in there. sti doesn't cost that much, and the work-to-do and sched_yield
paths are _never_ fast paths, so they don't worth an hack like that.