[Xen-devel] Re: [PATCH] blkfront: Move blkif_interrupt into a tasklet.

[Daniel Stodden <daniel.stodden@xxxxxxxxxx>]

This is upstream/xen/blkfront at
git://xenbits.xensource.com/people/dstodden/linux.git

Daniel

On Mon, 2010-08-23 at 02:54 -0400, Daniel Stodden wrote:
> Response processing doesn't really belong into hard irq context.
> 
> Another potential problem this avoids is that switching interrupt cpu
> affinity in Xen domains can presently lead to event loss, if
> RING_FINAL_CHECK is run from hard irq context.
> 
> Signed-off-by: Daniel Stodden <daniel.stodden@xxxxxxxxxx>
> Cc: Tom Kopec <tek@xxxxxxx>
> ---
>  drivers/block/xen-blkfront.c |   16 ++++++++++++++--
>  1 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 6c00538..75576d3 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -86,6 +86,7 @@ struct blkfront_info
>       struct blkif_front_ring ring;
>       struct scatterlist sg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
>       unsigned int evtchn, irq;
> +     struct tasklet_struct tasklet;
>       struct request_queue *rq;
>       struct work_struct work;
>       struct gnttab_free_callback callback;
> @@ -676,13 +677,14 @@ static void blkif_completion(struct blk_shadow *s)
>               gnttab_end_foreign_access(s->req.seg[i].gref, 0, 0UL);
>  }
>  
> -static irqreturn_t blkif_interrupt(int irq, void *dev_id)
> +static void
> +blkif_do_interrupt(unsigned long data)
>  {
> +     struct blkfront_info *info = (struct blkfront_info *)data;
>       struct request *req;
>       struct blkif_response *bret;
>       RING_IDX i, rp;
>       unsigned long flags;
> -     struct blkfront_info *info = (struct blkfront_info *)dev_id;
>       int error;
>  
>       spin_lock_irqsave(&info->io_lock, flags);
> @@ -743,6 +745,15 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
>  
>  out:
>       spin_unlock_irqrestore(&info->io_lock, flags);
> +}
> +
> +
> +static irqreturn_t
> +blkif_interrupt(int irq, void *dev_id)
> +{
> +     struct blkfront_info *info = (struct blkfront_info *)dev_id;
> +
> +     tasklet_schedule(&info->tasklet);
>  
>       return IRQ_HANDLED;
>  }
> @@ -893,6 +904,7 @@ static int blkfront_probe(struct xenbus_device *dev,
>       info->connected = BLKIF_STATE_DISCONNECTED;
>       INIT_WORK(&info->work, blkif_restart_queue);
>       spin_lock_init(&info->io_lock);
> +     tasklet_init(&info->tasklet, blkif_do_interrupt, (unsigned long)info);
>  
>       for (i = 0; i < BLK_RING_SIZE; i++)
>               info->shadow[i].req.id = i+1;



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