Re: scheduler support to lock user processes out?

[Matthias Drochner <M.Drochner%fz-juelich.de@localhost>]

imp%bsdimp.com@localhost said:
> : -FreeBSD acquires the big kernel lock before suspending
> :  devices, holding it all the time until after resume.
> For the record, this doesn't work well and is done only because the
> device tree's data structures are protected by Giant. 

You mean, it doesn't work well because it is not a 100%
protection against other code interfering with the
suspend process, or does it have bad side effects?

In my experience, while NetBSD doesn't protect the
device tree either, this was less a problem. I often
got "fp save ipi didn't" panics w/o the biglock, which
might eg. be caused by a CPU reading nonsense from a
suspended device, causing it to spin in a loop.
With the biglock, suspending works perfectly well
on my dual-core.
(I'm not questioning that correct locking everywhere
would be preferrable.)

best regards
Matthias




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