On Tue, Mar 6, 2012 at 12:26 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>
> Subject: genirq: Clear action->thread_mask if IRQ_ONESHOT is not set
Umm. Apparently this patch fixes the bug, but the patch itself is just insane.
> - if (new->flags & IRQF_ONESHOT && thread_mask == ~0UL) {
> - ret = -EBUSY;
> - goto out_mask;
> + if (new->flags & IRQF_ONESHOT) {
> + if (thread_mask == ~0UL) {
> + ret = -EBUSY;
> + goto out_mask;
> + }
> + new->thread_mask = new->flags & IRQF_ONESHOT;
> }
> - new->thread_mask = 1 << ffz(thread_mask);
WHAT?
You just checked that "new->flags & IRQF_ONESHOT" nonzero, and inside
that if-statement, you then do
new->thread_mask = new->flags & IRQF_ONESHOT;
which is just crazy. Why don't you just do
new->thread_mask = IRQF_ONESHOT;
if that is what you actually meant?
What is that code actually *supposed* to do?
Also, what was the meaning of that old insane line:
new->thread_mask = 1 << ffz(thread_mask);
which you removed? It was crap, I agree, but what was the thinking
behind it? And the reason it was crap is because that's a crazy
expression that could be written better ways (*), and it needs a
comment on what the heck the point of it was..
So stop with these "random code" snippets, and explain what the f*&^
the code is meant to do, AND THEN WRITE THE CODE IN A SANE MANNER
instead of posting these kinds of insane patches.
Because right now it really looks like the "random monkey" approach to
programming.
Linus
(*) "1 << ffz(a)" can be written as
a = ~a; /* Turn the zero bits into 1 bits */
a &= -a; /* .. and find the first one. */
without ever doing any insane bit scanning.
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