Re: [patch 1/3] mmu_notifier: Core code

From: Christoph Lameter
Date: Thu Jan 31 2008 - 22:03:54 EST


On Thu, 31 Jan 2008, Jack Steiner wrote:

> I currently unlink the mmu_notifier when the last GRU mapping is closed. For
> example, if a user does a:
>
> gru_create_context();
> ...
> gru_destroy_context();
>
> the mmu_notifier is unlinked and all task tables allocated
> by the driver are freed. Are you suggesting that I leave tables
> allocated until the task terminates??

You are in user space and calling into the kernel somehow. The
mmap_sem is not held at that point so its no trouble to use the unregister
function. After that wait for rcu and then free your tables.

> I assumed that I would need to use call_rcu() or synchronize_rcu()
> before the table is actually freed. That's still on my TODO list.

Right.

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