Re: [Lse-tech] Re: [PATCH for 2.5] preemptible kernel

> > But if you are suppressing preemption in all read-side critical sections, > > then wouldn't any already-preempted tasks be guaranteed to -not- be in > > a read-side critical section, and therefore be guaranteed to be unaffected > > by the update (in other words, wouldn't such tasks not need t

Re: [Lse-tech] Re: [PATCH for 2.5] preemptible kernel

In message you write: > > Already preempted tasks. > > But if you are suppressing preemption in all read-side critical sections, > then wouldn't any already-preempted tasks be guaranteed to -not- be in > a read-side critical section, and there

Re: [Lse-tech] Re: [PATCH for 2.5] preemptible kernel

On Tue, 10 Apr 2001 [EMAIL PROTECTED] wrote: > On Tue, Apr 10, 2001 at 09:08:16PM -0700, Paul McKenney wrote: > > > Disabling preemption is a possible solution if the critical section is > > short > > > - less than 100us - otherwise preemption latencies become a problem. > > > > Seems like a reas

Re: [Lse-tech] Re: [PATCH for 2.5] preemptible kernel

On Tue, 10 Apr 2001, Paul McKenney wrote: > > Disabling preemption is a possible solution if the critical section > > is > short > > - less than 100us - otherwise preemption latencies become a problem. > > Seems like a reasonable restriction. Of course, this same limit > applies to locks and int

Re: [Lse-tech] Re: [PATCH for 2.5] preemptible kernel

On Tue, Apr 10, 2001 at 09:08:16PM -0700, Paul McKenney wrote: > > Disabling preemption is a possible solution if the critical section is > short > > - less than 100us - otherwise preemption latencies become a problem. > > Seems like a reasonable restriction. Of course, this same limit applies >

Re: [Lse-tech] Re: [PATCH for 2.5] preemptible kernel

> On Tue, 10 Apr 2001, Paul McKenney wrote: > > The algorithms we have been looking at need to have absolute guarantees > > that earlier activity has completed. The most straightforward way to > > guarantee this is to have the critical-section activity run with preemption > > disabled. Most of

Re: [Lse-tech] Re: [PATCH for 2.5] preemptible kernel

On Tue, 10 Apr 2001, Paul McKenney wrote: > The algorithms we have been looking at need to have absolute guarantees > that earlier activity has completed. The most straightforward way to > guarantee this is to have the critical-section activity run with preemption > disabled. Most of these code

Re: [Lse-tech] Re: [PATCH for 2.5] preemptible kernel

> > As you've observed, with the approach of waiting for all pre-empted tasks > > to synchronize, the possibility of a task staying pre-empted for a long > > time could affect the latency of an update/synchonize (though its hard for > > me to judge how likely that is). > > It's very unlikely on a

Re: [Lse-tech] Re: [PATCH for 2.5] preemptible kernel

On Mon, 9 Apr 2001 [EMAIL PROTECTED] wrote: > As you've observed, with the approach of waiting for all pre-empted tasks > to synchronize, the possibility of a task staying pre-empted for a long > time could affect the latency of an update/synchonize (though its hard for > me to judge how likely th

Re: [Lse-tech] Re: [PATCH for 2.5] preemptible kernel

>One question: >isn't it the case that the alternative to using synchronize_kernel() >is to protect the read side with explicit locks, which will themselves >suppress preemption? If so, why not just suppress preemption on the read >side in preemptible kernels, and thus gain the simpler implement

Re: [Lse-tech] Re: [PATCH for 2.5] preemptible kernel

> > > > 2. Isn't it possible to get in trouble even on a UP if a task > > > > is preempted in a critical region? For example, suppose the > > > > preempting task does a synchronize_kernel()? > > > > > > Ugly. I guess one way to solve it would be to readd the 2.2 scheduler > > > taskq

Re: [Lse-tech] Re: [PATCH for 2.5] preemptible kernel

> > I see your point here, but need to think about it. One question: > > isn't it the case that the alternative to using synchronize_kernel() > > is to protect the read side with explicit locks, which will themselves > > suppress preemption? If so, why not just suppress preemption on the read >

Re: [Lse-tech] Re: [PATCH for 2.5] preemptible kernel

On Fri, Apr 06, 2001 at 06:25:36PM -0700, Paul McKenney wrote: > I see your point here, but need to think about it. One question: > isn't it the case that the alternative to using synchronize_kernel() > is to protect the read side with explicit locks, which will themselves > suppress preemption?