RE: [PATCH 4/9] mpt fusion: error recovery improvements, andsynchronizing internal commands

[James Bottomley <James.Bottomley@SteelEye.com>]

On Mon, 2007-09-24 at 19:26 -0600, Moore, Eric wrote:
> On Saturday, September 22, 2007 9:39 AM,  James Bottomley wrote:
> > 
> > Well, I'll put this in this time.  However, it contains a 
> > whole slew of
> > pointless changes like this:
> > 
> > 
> > > -                       mdelay (10);
> > > +                       udelay (10000);
> > 
> > and
> > 
> > > -               mdelay(1);
> > > +               udelay(1000);
> > 
> > Which is going to excite the janitors into a frenzy of replace udelay
> > with mdelay patches, which I can well do without ... please don't do
> > this type of change unless there's some actual reason for it.
> > 
> 
> I recall the reason for this change.  I found that medlay called during
> interrupt context didn't work well, whereas udelay did.  Oringally when
> mpt_fault_reset_work was added, this code was called using timers, which
> as you know, is called as part of softirq bottom half handler.  Since
> then, we converted mpt_fault_reset_work to being called using user
> context work task, so really its a non-issue I guess.

That shouldn't have happened ... if you look (include/linux/delay.h)
mdelay is implemented in terms of udelay, so the behaviour should be the
same.

There is a technical difference, though.  Because udelay is busy waiting
in a calculated processor loop, it can overflow for large values (and
large is defined to be anything > 1000) mdelay() is careful to call
udelay multiple times to avoid the potential overflow.

James