linux-kernel - Re: [PATCH] drm/ttm: remove unneeded preempt

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Date:	Wed, 14 Nov 2012 09:54:06 +0100
From:	Thomas Hellstrom <thellstrom@...are.com>
To:	Akinobu Mita <akinobu.mita@...il.com>
CC:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/ttm: remove unneeded preempt_disable/enable

On 11/09/2012 01:10 PM, Akinobu Mita wrote:
> It is unnecessary to disable preemption explicitly while calling
> copy_highpage().  Because copy_highpage() will do it again through
> kmap_atomic/kunmap_atomic.
>
> Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
> Cc: dri-devel@...ts.freedesktop.org
> Cc: David Airlie <airlied@...ux.ie>
> ---
>   drivers/gpu/drm/ttm/ttm_tt.c | 4 ----
>   1 file changed, 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
> index bf82601..7d759a4 100644
> --- a/drivers/gpu/drm/ttm/ttm_tt.c
> +++ b/drivers/gpu/drm/ttm/ttm_tt.c
> @@ -308,9 +308,7 @@ int ttm_tt_swapin(struct ttm_tt *ttm)
>   		if (unlikely(to_page == NULL))
>   			goto out_err;
>   
> -		preempt_disable();
>   		copy_highpage(to_page, from_page);
> -		preempt_enable();
>   		page_cache_release(from_page);
>   	}
>   
> @@ -358,9 +356,7 @@ int ttm_tt_swapout(struct ttm_tt *ttm, struct file *persistent_swap_storage)
>   			ret = PTR_ERR(to_page);
>   			goto out_err;
>   		}
> -		preempt_disable();
>   		copy_highpage(to_page, from_page);
> -		preempt_enable();
>   		set_page_dirty(to_page);
>   		mark_page_accessed(to_page);
>   		page_cache_release(to_page);

Reviewed-by: Thomas Hellstrom <thellstrom@...are.com>

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