Re: [regression] Crash in wb_clear_pending()

From: Christoph Hellwig
Date: Tue Jul 06 2010 - 21:47:55 EST


On Tue, Jul 06, 2010 at 08:47:33AM +0200, Ingo Molnar wrote:
> Yeah, i agree - especially since the smaller patch is still pretty large (not
> a oneliner), plus it does not appear that the precise failure mode is fully
> understood either.

The two failure modes we saw are very precicely understood:

- access to ->state after it's been freed
- access to ->state after the caller which has the bdi_work struct on
stack has been woken up.

But I seriously fear that there are even more dragons hidden in this
maze of bit wakeups and rcu, so replacing it with a proper completion
seems by far safer to me.

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