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SubjectRe: [patch] disable_bh/enable_bh race fix [Re: Program to freeze keyboard in 2.1.131]


On Mon, 28 Dec 1998, Andrea Arcangeli wrote:
>
> But now I can' t see again why we doesn't wait_on_bh in synchronize_bh if
> we are running in a irq handler...

Basically, think about the interactions of

CPU#1 CPU#2

irq handler bottom half handler
wait_on_bh(); cli();

and I've solved it by simply prioiritizing in a very simple manner:
hardware interrupts have "higher priority" than bottom half handlers, and
as such a hardware interrupt will never wait for a bottom half handler.
Deadlock avoided.

Linus


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