[RFC] Make SMP secondary CPU up more resilient to failure.

[Andrei Warkentin]

On Thu, Jan 13, 2011 at 5:14 AM, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
>
> On Thu, Jan 13, 2011 at 04:19:40AM -0600, Andrei Warkentin wrote:
> > I fully agree. Would you be interested in me bringing back the actual
> > synchronization code from platform-dependent code into the preinit
> > function and posting that as a patch for review?
>
> I really don't like the idea of a preinit function - it's completely
> unnecessary as I've been trying to point out.  It has been shown that
> it takes a hundred or so microseconds to get into the kernel, and
> then a couple of hundred milliseconds to run the delay loop.
>
> As platforms are expected to wait in their boot_secondary() for the
> first half - currently platforms wait one second - we're talking
> about around a hundred microseconds vs a timeout of one second.
> That's a factor of 10000 beyond what's required.
>
> It has also been shown that the problem you were seeing was down to
> synchronization/delayed write bugs which have since been solved - and
> adding yet more synchronization is not the answer to buggy
> synchronization.
>
> So, as the timeouts are already well in excess and the root cause of
> your problem has been resolved, I see no need to make this stuff more
> complex - the more complexity there is, the more chance there is of
> things going wrong.

Fair enough :).