linux-kernel - Re: [PATCH] cpuset and sched domains: sched_load

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Message-Id: <20071002135756.6eca39e0.pj@sgi.com>
Date:	Tue, 2 Oct 2007 13:57:56 -0700
From:	Paul Jackson <pj@....com>
To:	Randy Dunlap <randy.dunlap@...cle.com>
Cc:	akpm@...ux-foundation.org, nickpiggin@...oo.com.au,
	menage@...gle.com, linux-kernel@...r.kernel.org, dino@...ibm.com,
	cpw@....com, mingo@...e.hu
Subject: Re: [PATCH] cpuset and sched domains: sched_load_balance flag

Thanks for the review, Randy.  Good comments.

> > Acked-by: Paul Jackson <pj@....com>
> 
> Are there some attributions missing, else S-O-B ?

Yup - I should have written this line as:

	Signed-off-by: Paul Jackson <pj@....com>

> > +static int cpusets_overlap(struct cpuset *a, struct cpuset *b)
> 
> inline ?

It makes no difference to the code generated.  I tend to leave
out 'compiler optimization' hint words if I don't need them to
get the compiler to optimize.  In this case, of a single use
file static routine, the compiler inlines anyway.

> > +	q = NULL; csa = NULL; doms = NULL;
> 
> That's not kernel style.  Use either (Andrew would say the second one):
> 
> 	q = csa = doms = NULL;
> 
> or
> 	q = NULL;
> 	csa = NULL;
> 	doms = NULL;

You're right - and Andrew would be right as well, since the form:

	q = csa = doms = NULL;

generates a compiler warning, as not all three pointers are the
same type.

So three lines of code it must be.

> > +	if (q && !IS_ERR(q))
> > +		kfree(q);
> > +	if (csa)
> 
> Don't need the conditional: kfree(NULL) is OK.

Yup - you're right - about the 'csa' check.

However the if(q ...) check is needed, because I have another bug
here.  I allocated 'q' using kfifo_alloc(), so must free using
kfifo_free (or else leak the kfifo buffer memory.)  Calls to
kfifo_free() have to guard against NULL pointers before the call.

Thanks, Randy!

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@....com> 1.925.600.0401
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