Re: [PATCH scsi-misc-2.6 04/13] scsi: remove meaningless volatile qualifiers from structure definitions

[Christoph Hellwig <hch@infradead.org>]

On Thu, Mar 31, 2005 at 06:08:10PM +0900, Tejun Heo wrote:
>  	struct list_head    siblings;   /* list of all devices on this host */
>  	struct list_head    same_target_siblings; /* just the devices sharing same target id */
>  
> -	volatile unsigned short device_busy;	/* commands actually active on low-level */
> +	unsigned short device_busy;	/* commands actually active on
> +					 * low-level. protected by sdev_lock. */

You should probably switch it to just unsigned.  The other 16bit are wasted
due to alignment anyway, and some architectures produce better code for 32bit
accesses.

> -	volatile unsigned short host_busy;   /* commands actually active on low-level */
> -	volatile unsigned short host_failed; /* commands that failed. */
> +
> +	/*
> +	 * The following two fields are protected with host_lock;
> +	 * however, eh routines can safely access during eh processing
> +	 * without acquiring the lock.
> +	 */
> +	unsigned short host_busy;	   /* commands actually active on low-level */
> +	unsigned short host_failed;	   /* commands that failed. */

Here it would actually increase the struct size but might make sense anyway.

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