Re: SMP problem with (en|dis)able_bh().

MOLNAR Ingo (mingo@chiara.csoma.elte.hu)
Wed, 13 Jan 1999 16:48:27 +0100 (CET)


On Mon, 11 Jan 1999, Patrik Rak wrote:

> Now imagine the situation when processor A is going to disable bottom
> halves, while B is going to enable it. Now it might go like this (note
> that many other similar scenarios are possible):
>
> A clears the bit in bh_mask
>
> B decrements bh_mask_count
>
> B sets the bit in bh_mask
>
> A increments bh_mask_count
>
> So, the result is that A thinks that the particular bottom half handler is
> disabled but it actually is not.

fortunately only the console code uses this function, which is mostly
protected by the kernel lock. So i dont think this is an 'active' bug, but
good spotting nevertheless ...

-- mingo

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