Re: random.c changes for sparse irq_desc are crap

[Yinghai Lu]

On Wed, Dec 31, 2008 at 3:40 PM, Matt Mackall <mpm@xxxxxxxxxxx> wrote:
> On Wed, 2008-12-31 at 15:07 -0800, Yinghai Lu wrote:
>> Matt Mackall wrote:
>> > I just noticed you merged a change that pointlessly converts two
>> > random.c functions into ugly random.h inlines without going through the
>> > maintainer.
>> >
>> > I also don't like the look of the newly-introduced sparse variants of
>> > these functions. Failure to find an irq descriptor in
>> > get_timer_rand_state is a BUG_ON should-never-happen sort of condition,
>> > not something to silently ignore. Letting the code try to dereference
>> > NULL is preferred here: we'll actually be able to find and fix the
>> > broken driver that's throwing around meaningless irq vectors.
>> >
>> > Throwing away the timer_state pointer in the set_timer_rand_state
>> > function is similarly bogus in addition to being a memory leak.
>> >
>> > Please fix this up.
>> >
>>
>> want something like this?
>
> Not quite.
>
> First, please turn these back into normal functions in random.c.
> Inlining functions is generally discouraged these days unless you have a
> good reason and numbers to back it up.

Ingo wanted to hide that #ifdef to .h

>
> Second, as I tried to explain above, BUG_ON(!desc) is doing very little
> that the subsequent desc->timer_rand_state wouldn't already do
> (generating a traceback). In cases where dereferencing NULL should never
> happen, it's preferable to not add the extra check and just let the oops
> happen. We'll still get a backtrace if anything ever goes wrong, but we
> won't have wasted any code space or CPU cycles when it doesn't.

ok

YH
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