linux-kernel - Re: [patch 1/3] mmu

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Date:	Thu, 31 Jan 2008 19:03:43 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Jack Steiner <steiner@....com>
Subject: Re: [patch 1/3] mmu_notifier: Core code

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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