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DateFri, 7 Jan 2011 00:32:41 -0800
From"Paul E. McKenney" <>
SubjectRe: [GIT PULL] RCU changes for v2.6.38
On Fri, Jan 07, 2011 at 12:54:57AM +0100, Ingo Molnar wrote:
>
> * Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
> > On Thu, Jan 6, 2011 at 1:08 AM, Ingo Molnar <mingo@elte.hu> wrote:
> > >
> > > Please pull the latest core-rcu-for-linus git tree from:
> >
> > So I pulled, but I'm not convinced about the crazy busy-looping
> > SRCU_SYNCHRONIZE_DELAY thing.
> >
> > Why does it do a silly udelay(), instead of just looping over the
> > srcu_readers_active_idx() for a few times? You're wasting CPU time
> > anyway, why ask the user how many usecs to waste?
> >
> > IOW, why isn't that "wait for no active readers" a nice helper
> > function, and why doesn't it do
> >
> > for (i = 0; i < CONFIG_SRCU_SYNCHRONIZE_DELAY; i++) {
> > if (!srcu_readers_active_idx(sp, idx))
> > return;
> > udelay(1);
> > }
> > while (srcu_readers_active_idx(sp, idx))
> > schedule_timeout_interruptible(1);
> >
> > instead? And is it really sane to ask the kernel configurator to come
> > up with a random value (ie that "CONFIG_SRCU_SYNCHRONIZE_DELAY" is
> > just stupid and wrong)?
> >
> > Please fix this. And don't make people answer unanswerable questions.
> > If YOU and Paul don't know the answer, why the hell do you expect
> > somebody who does a "make config" to know the answer?
> >
> > Either pick a number, or pick an algorithm that self-tunes.
> >
> > Don't use the Kconfig system as a way to tell people that it's their
> > fault when you made a bad decision. Really.
>
> Fully agreed - we'll fix this.

I am on it!

Thanx, Paul


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