diff mbox

IRQF_SAMPLE_RANDOM question...

Message ID 200904090954.54601.rgetz@blackfin.uclinux.org
State Not Applicable, archived
Delegated to: David Miller
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Commit Message

Robin Getz April 9, 2009, 1:54 p.m. UTC 
On Wed 8 Apr 2009 15:51, Matt Mackall pondered:
> On Tue, 2009-04-07 at 17:44 -0400, Robin Getz wrote:
> > Is that "Everything in general, with a few exceptions", or
> > "__Everything__"?
> 
> Everything. We want every input point to better document the type of
> entropy source.

OK - any objections to something like this?

something like:

--------
ERROR: Don't use IRQF_SAMPLE_RANDOM(): see 
Documentation/feature-removal-schedule.txt
#10: FILE: serial/bfin_5xx.c:650:
+       if (request_irq(uart->port.irq, bfin_serial_rx_int, IRQF_DISABLED | 
IRQF_SAMPLE_RANDOM,
--------

My only real question is on the date... In a previous email:

On Mon 6 Apr 2009 15:01, Matt Mackall pondered:
> I'm eventually going to move the RNG away from the strict theoretical
>  entropy accounting model to a more pragmatic one which will be much
>  happier with iffy entropy sources, but that's a ways off.

I was not sure what "a ways off" was defined as - or are the two (removal of 
IRQF_SAMPLE_RANDOM, and the pragmatic entropy accounting model) separate in 
your mind? I guess various add_*_randomness functions can be added today, and 
change how they are accounted for in the future?

-Robin
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Comments

Matt Mackall April 9, 2009, 5 p.m. UTC | #1 
On Thu, 2009-04-09 at 09:54 -0400, Robin Getz wrote:
> On Wed 8 Apr 2009 15:51, Matt Mackall pondered:
> > On Tue, 2009-04-07 at 17:44 -0400, Robin Getz wrote:
> > > Is that "Everything in general, with a few exceptions", or
> > > "__Everything__"?
> > 
> > Everything. We want every input point to better document the type of
> > entropy source.
> 
> OK - any objections to something like this?

Hmm, this is a purely internal interface. Not sure if we need to bother
with scheduling it. My plan was to simply get the new code in and sweep
the kernel.
Robin Getz April 10, 2009, 12:41 a.m. UTC | #2 
On Thu 9 Apr 2009 13:00, Matt Mackall pondered:
> On Thu, 2009-04-09 at 09:54 -0400, Robin Getz wrote:
> > On Wed 8 Apr 2009 15:51, Matt Mackall pondered:
> > > On Tue, 2009-04-07 at 17:44 -0400, Robin Getz wrote:
> > > > Is that "Everything in general, with a few exceptions", or
> > > > "__Everything__"?
> > > 
> > > Everything. We want every input point to better document the type of
> > > entropy source.
> > 
> > OK - any objections to something like this?
> 
> Hmm, this is a purely internal interface. Not sure if we need to bother
> with scheduling it. My plan was to simply get the new code in and sweep
> the kernel. 

Yeah - it just stops people from putting in more places you need to change 
later.
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Chris Peterson April 10, 2009, 1:29 a.m. UTC | #3 
> Hmm, this is a purely internal interface. Not sure if we need to bother
> with scheduling it. My plan was to simply get the new code in and sweep
> the kernel.

Matt, sounds like you're volunteering? :)

From my understanding, the roadmap looks something like:

1. Add checkpatch warning about IRQF_SAMPLE_RANDOM
2. Add any new add_*_randomness() functions (e.g. RTC and main clocks?
Serial or USB interrupts?)
3. Remove IRQF_SAMPLE_RANDOM macro (and checkpatch warning)
4. Add "pragmatic entropy accounting model"?


chris
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Matt Mackall April 10, 2009, 2:27 a.m. UTC | #4 
On Thu, 2009-04-09 at 18:29 -0700, Chris Peterson wrote:
> > Hmm, this is a purely internal interface. Not sure if we need to bother
> > with scheduling it. My plan was to simply get the new code in and sweep
> > the kernel.
> 
> Matt, sounds like you're volunteering? :)
> 
> >From my understanding, the roadmap looks something like:
> 
> 1. Add checkpatch warning about IRQF_SAMPLE_RANDOM
> 2. Add any new add_*_randomness() functions (e.g. RTC and main clocks?
> Serial or USB interrupts?)
> 3. Remove IRQF_SAMPLE_RANDOM macro (and checkpatch warning)
> 4. Add "pragmatic entropy accounting model"?

Yeah, I just sat down with Ted Tso this evening and hashed out a new
design. More to come.
diff mbox

Patch

===================================================================
--- Documentation/feature-removal-schedule.txt  (revision 6236)
+++ Documentation/feature-removal-schedule.txt  (working copy)
@@ -6,6 +6,19 @@ 

 ---------------------------

+What:  IRQF_SAMPLE_RANDOM
+Check: IRQF_SAMPLE_RANDOM
+When:  July 2009
+Why:   Many of IRQF_SAMPLE_RANDOM users are technically bogus as entropy
+       sources in the kernel's current entropy model. To resolve this, every
+       input point to the kernel's entropy pool needs to better document the
+       type of entropy source it actually is. This will be replaced with
+       additional add_*_randomness functions in drivers/char/random.c
+
+Who:   Robin Getz <rgetz@blackfin.uclinux.org> & Matt Mackall 
<mpm@selenic.com>
+
+---------------------------
+

Then if someone attempts to add it, and runs checkpatch, it will generate