linux-kernel - Re: [PATCH] iommu/amd: Use wait_event in put_pasid_state

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Message-ID: <20150204163450.GD5029@twins.programming.kicks-ass.net>
Date:	Wed, 4 Feb 2015 17:34:50 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Joerg Roedel <joro@...tes.org>
Cc:	iommu@...ts.linux-foundation.org,
	Benjamin LaHaise <bcrl@...ck.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>, linux-aio@...ck.org,
	linux-kernel@...r.kernel.org, Oded Gabbay <oded.gabbay@....com>,
	jroedel@...e.de
Subject: Re: [PATCH] iommu/amd: Use wait_event in put_pasid_state_wait

On Wed, Feb 04, 2015 at 04:10:22PM +0100, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@...e.de>
> 
> Now that I learned about possible spurious wakeups this
> place needs fixing too. Replace the self-coded sleep variant
> with the generic wait_event() helper.
> 
> Signed-off-by: Joerg Roedel <jroedel@...e.de>
> ---
>  drivers/iommu/amd_iommu_v2.c | 9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
> 
> diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
> index b6398d7..5cc1409 100644
> --- a/drivers/iommu/amd_iommu_v2.c
> +++ b/drivers/iommu/amd_iommu_v2.c
> @@ -266,14 +266,7 @@ static void put_pasid_state(struct pasid_state *pasid_state)
>  
>  static void put_pasid_state_wait(struct pasid_state *pasid_state)
>  {
> -	DEFINE_WAIT(wait);
> -
> -	prepare_to_wait(&pasid_state->wq, &wait, TASK_UNINTERRUPTIBLE);
> -
> -	if (!atomic_dec_and_test(&pasid_state->count))
> -		schedule();
> -
> -	finish_wait(&pasid_state->wq, &wait);
> +	wait_event(pasid_state->wq, !atomic_read(&pasid_state->count));
>  	free_pasid_state(pasid_state);
>  }

You just lost your atomic_dec.
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