Messages in this thread | | | Date | Tue, 27 May 2008 10:06:11 -0700 | From | "Paul E. McKenney" <> | Subject | Re: 2.6.26-rc4: RIP find_pid_ns+0x6b/0xa0 |
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On Tue, May 27, 2008 at 09:11:33AM -0700, Linus Torvalds wrote: > On Tue, 27 May 2008, Paul E. McKenney wrote: > > > > But this will only help until preemptible spinlocks arrive, right? > > I don't think we will ever have preemptible spinlocks. > > If you preempt spinlocks, you have serious issues with contention and > priority inversion etc, and you basically need to turn them into sleeping > mutexes. So now you also need to do interrupts as sleepable threads etc > etc.
Indeed, all of these are required in that case.
> And it would break the existing non-preempt RCU usage anyway.
Yes, preemptable spinlocks cannot work without preemptable RCU.
> Yeah, maybe the RT people try to do that, but quite frankly, it is insane. > Spinlocks are *different* from sleeping locks, for a damn good reason.
Well, I guess I never claimed to be sane...
Anyway, will look at a preemptable RCU that waits for preempt-disable sections of code.
Thanx, Paul
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