Re: [PATCH 1/7] block: Avoid that blk_drain_queue() finishes early

[Tejun Heo <tj@kernel.org>]

On Sun, Oct 28, 2012 at 06:47:22PM -0700, Tejun Heo wrote:
> Hello,
> 
> On Fri, Oct 26, 2012 at 02:01:23PM +0200, Bart Van Assche wrote:
> > Code like "drain |= q->nr_rqs[i]" might result in blk_drain_queue()
> > to finish early if the expression at the RHS is a multiple of 256
> > since the drain variable is only eight bits wide. Avoid this by
> > changing the type of the drain variable from bool into unsigned.
> 
> No, it doesn't happen that way.  One of the reasons we have bool at
> all is to avoid this type of problems caused by implicit type-casting.
> 
> Why do you keep pushing this?  It's WRONG.  Please drop it.

>From C99 std draft.

 6.3 Conversions
 6.3.1.2 Boolean type

  When any scalar value is converted to _Bool, the result is 0 if the
  value compares equal to 0; otherwise, the result is 1.

It doesn't care the width or signedness of the type being converted.
If the origin value equals zero, it converts to 0; otherwise 1.

Thanks.

-- 
tejun