linux-kernel - Re: [PATCH] dmaengine: pl330: initialize tasklet after spin_unlock

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Message-ID: <CAJKOXPfpD79R53VYDXB4hk0JFkC2L2pEHy7ihWwnn9DJMwxZ1A@mail.gmail.com>
Date:	Fri, 19 Feb 2016 15:06:49 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Anand Moon <linux.amoon@...il.com>
Cc:	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: pl330: initialize tasklet after spin_unlock_irqrestore

2016-02-19 2:21 GMT+09:00 Anand Moon <linux.amoon@...il.com>:
> From: Anand Moon <linux.amoon@...il.com>
>
> pl330_tasklet tasklet uses the same spinlock pch->lock for safe IRQ locking.
> It's safe to initialize pl330_tasklet tasklet after release of the locking.

This is tasklet init, not tasklet execution (which you are referring
to in first sentence). I don't get how usage of spinlock during
execution guarantees the safeness during init... Please describe why
this is safe.

Best regards,
Krzysztof

>
> Signed-off-by: Anand Moon <linux.amoon@...il.com>
> ---
>  drivers/dma/pl330.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> index 17ee758..df2cab1 100644
> --- a/drivers/dma/pl330.c
> +++ b/drivers/dma/pl330.c
> @@ -2091,10 +2091,10 @@ static int pl330_alloc_chan_resources(struct dma_chan *chan)
>                 return -ENOMEM;
>         }
>
> -       tasklet_init(&pch->task, pl330_tasklet, (unsigned long) pch);
> -
>         spin_unlock_irqrestore(&pch->lock, flags);
>
> +       tasklet_init(&pch->task, pl330_tasklet, (unsigned long) pch);
> +
>         return 1;
>  }
>
> --
> 1.9.1
>
> --
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