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

[Andrew Morton]

Andrea Arcangeli <andrea@xxxxxxx> wrote:
>
> > Sleeping with local interrupts disabled is usually a bug, so we should
> > prefer to keep that check in might_sleep().
> 
> either it's _always_ a bug including for entry.S or sched_yield, or it's
> _never_ a bug. I don't understand the "usually".

If some code does:


	local_irq_disable();
	<fiddle with per-cpu stuff>
	kmalloc(GFP_KERNEL);
	<fiddle with per-cpu stuff>
	local_irq_enable();

or

	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.

The fact that a couple of scheduler-internal fastpaths happen to know that
they can call schedule() with interrupts disabled is not relevant to this.
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