Please review all modules for unload races

[willy en thepuffingroup.com]

On Sun, Jan 30, 2000 at 07:09:00PM +1100, Keith Owens wrote:
> 	static int open_foo(struct inode *inode, struct file *file)
> 	{
> 		MOD_INC_USE_COUNT;	/* must be first */
> 		if (request_irq(FOO_IRQ, foo_interrupt, 0, "FOO", NULL)) {
> 			MOD_DEC_USE_COUNT;	/* failure path */
> 			return -EBUSY;
> 		}
> 		return 0;
> 	}

>From a performance and readability PoV, the following idiom is generally
preferred:

	static int open_foo(struct inode *inode, struct file *file)
	{
		int retval;
		MOD_INC_USE_COUNT;
		retval = -EBUSY;
		if (request_irq(FOO_IRQ, foo_interrupt, 0, "FOO", NULL))
			goto fail;
		return 0;
	fail:
		MOD_DEC_USE_COUNT;
		return retval;
	}

This keeps the failure (uncommon) case out of the normal path and ensures
that _all_ failing calls call MOD_DEC_USE_COUNT.  I'm quite a big fan of
`only two return statements per function' because it allows for easier
printk-based debugging.  Oh, and it drives the anti-goto fanatics wild,
so it's also worthwhile.


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