Re: [PATCH] arm: sched: stop sched_clock() during suspend

[Kevin Hilman <khilman@deeprootsystems.com>]

Russell King - ARM Linux <linux@arm.linux.org.uk> writes:

> On Tue, Oct 23, 2012 at 12:28:32AM +0200, Linus Walleij wrote:
>> On Mon, Oct 22, 2012 at 7:05 PM, Kevin Hilman
>> <khilman@deeprootsystems.com> wrote:
>> 
>> > However, in light of RT throttling, this a correctness issue for process
>> > accounting, so I agree that this should be done for all platforms
>> > instead of providing an optional 'needs suspend' version of the API,
>> > even though it means printk times no longer reflect time spent
>> > suspended.
>> 
>> Maybe we should get printk() to use the best clocksource
>> instead.
>> 
>> The reason AFAICT that printk() is using sched_clock() is that
>> it's supposed to be fast. But now it seems that it's not going
>> to return what printk() needs anymore.
>
> No, printk() does not need this.  You think it does, but it doesn't.  What
> we have is a difference between ARM and x86, and this difference is breaking
> the scheduler.
>
> The fact that the printk timestamp increments while suspended is a bug.  It
> doesn't on x86.

Russell, I agree that it's a bug, but does it qualify as a something
you're willing to take for v3.7-rc?

For OMAP, we need to know if this will go for v3.7 or not because
there's a regression in the OMAP I2C driver, and if this doesn't go in,
we'll need to revert something in the I2C driver until it does.

Thanks,

Kevin