From: "Paul E. McKenney" <paulmck@us.ibm.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: linux-kernel@vger.kernel.org, Esben Nielsen <simlo@phys.au.dk>
Subject: Re: [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-07
Date: Wed, 23 Mar 2005 23:46:13 -0800 [thread overview]
Message-ID: <20050324074613.GJ1298@us.ibm.com> (raw)
In-Reply-To: <20050324053456.GA14494@elte.hu>
On Thu, Mar 24, 2005 at 06:34:56AM +0100, Ingo Molnar wrote:
>
> * Paul E. McKenney <paulmck@us.ibm.com> wrote:
>
> > Now, it is true that CPU#2 might record a quiescent state during this
> > time, but this will have no effect because -all- CPUs must pass
> > through a quiescent state before any callbacks will be invoked. Since
> > CPU#1 is refusing to record a quiescent state, grace periods will be
> > blocked for the full extent of task 1's RCU read-side critical
> > section.
>
> ok, great. So besides the barriers issue (and the long grace period time
> issue), the current design is quite ok. And i think your original flip
> pointers suggestion can be used to force synchronization.
The thing I am currently struggling with on the flip-pointers approach is
handling races between rcu_read_lock() and the flipping. In the earlier
implementations that used this trick, you were guaranteed that if you were
executing concurrently with one flip, you would do a voluntary context
switch before the next flip happened, so that the race was harmless.
This guarantee does not work in the PREEMPT_RT case, so more thought
will be required. :-/
Thanx, Paul
next prev parent reply other threads:[~2005-03-24 7:46 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-03-19 19:16 [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-00 Ingo Molnar
2005-03-20 0:24 ` Lee Revell
2005-03-21 15:42 ` K.R. Foley
2005-03-20 1:33 ` Lee Revell
2005-03-20 1:50 ` K.R. Foley
2005-03-20 4:32 ` Lee Revell
2005-03-20 22:40 ` Paul E. McKenney
2005-03-20 17:45 ` Paul E. McKenney
2005-03-21 8:53 ` Ingo Molnar
2005-03-21 9:01 ` Ingo Molnar
2005-03-21 9:06 ` [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-01 Ingo Molnar
2005-03-21 23:10 ` Magnus Naeslund(t)
2005-03-22 5:40 ` Paul E. McKenney
2005-03-22 8:50 ` Ingo Molnar
2005-03-22 13:56 ` Magnus Naeslund(t)
2005-03-23 5:46 ` Paul E. McKenney
2005-03-22 5:43 ` Paul E. McKenney
2005-03-22 7:24 ` Ingo Molnar
2005-03-22 9:23 ` Ingo Molnar
2005-03-22 9:32 ` Ingo Molnar
2005-03-22 10:01 ` [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-05 Ingo Molnar
2005-03-22 11:28 ` [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-07 Ingo Molnar
2005-03-22 15:06 ` K.R. Foley
2005-03-22 18:05 ` Magnus Naeslund(t)
2005-03-23 6:16 ` Paul E. McKenney
2005-03-23 6:33 ` Ingo Molnar
2005-03-23 6:37 ` Ingo Molnar
2005-03-24 6:06 ` Paul E. McKenney
2005-03-23 7:16 ` Ingo Molnar
2005-03-23 7:54 ` Steven Rostedt
2005-03-23 7:58 ` Ingo Molnar
2005-03-23 8:29 ` Peter Zijlstra
2005-03-23 9:03 ` Ingo Molnar
2005-03-24 6:45 ` Paul E. McKenney
2005-03-23 21:46 ` Ingo Molnar
2005-03-24 6:59 ` Paul E. McKenney
2005-03-24 6:38 ` Paul E. McKenney
2005-03-23 9:38 ` Herbert Xu
2005-03-23 9:49 ` Herbert Xu
2005-03-24 6:52 ` Paul E. McKenney
2005-03-24 5:28 ` Paul E. McKenney
2005-03-24 5:34 ` Ingo Molnar
2005-03-24 7:46 ` Paul E. McKenney [this message]
2005-03-24 8:31 ` Steven Rostedt
2005-03-24 8:47 ` Steven Rostedt
2005-03-24 10:45 ` Ingo Molnar
2005-03-24 11:39 ` Ingo Molnar
2005-03-24 14:33 ` Steven Rostedt
2005-03-24 17:51 ` Ingo Molnar
2005-03-24 18:17 ` Ingo Molnar
2005-03-24 23:05 ` Esben Nielsen
2005-03-25 6:19 ` Ingo Molnar
2005-03-26 16:31 ` Steven Rostedt
2005-03-26 19:11 ` Ingo Molnar
2005-03-26 16:04 ` Steven Rostedt
2005-03-30 6:31 ` Steven Rostedt
2005-03-30 6:50 ` Ingo Molnar
2005-03-30 16:46 ` Steven Rostedt
2005-03-30 19:44 ` Esben Nielsen
2005-03-30 19:56 ` Steven Rostedt
2005-03-30 21:39 ` Steven Rostedt
2005-03-30 21:43 ` Steven Rostedt
2005-03-31 11:03 ` Ingo Molnar
2005-03-31 12:03 ` Esben Nielsen
2005-03-31 12:14 ` Steven Rostedt
2005-03-31 13:33 ` Ingo Molnar
2005-03-31 12:22 ` Steven Rostedt
2005-03-31 12:36 ` Steven Rostedt
2005-03-31 12:58 ` Steven Rostedt
2005-03-31 13:28 ` Ingo Molnar
2005-03-31 12:49 ` Steven Rostedt
2005-03-31 14:10 ` Ingo Molnar
2005-03-31 17:41 ` Steven Rostedt
2005-03-31 17:49 ` Ingo Molnar
2005-03-31 18:17 ` Gene Heskett
2005-03-31 21:00 ` [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-07 (update) Gene Heskett
2005-03-31 20:22 ` [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-07 Steven Rostedt
2005-04-01 0:59 ` Steven Rostedt
2005-04-01 4:43 ` Ingo Molnar
2005-04-01 5:13 ` Steven Rostedt
2005-04-01 5:19 ` Ingo Molnar
2005-04-01 12:27 ` Steven Rostedt
2005-04-07 21:21 ` Steven Rostedt
2005-04-10 10:31 ` Ingo Molnar
2005-04-10 15:06 ` Steven Rostedt
2005-03-24 10:42 ` Ingo Molnar
2005-03-23 9:40 ` Herbert Xu
2005-03-23 9:48 ` Herbert Xu
2005-03-23 5:23 ` [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-05 Paul E. McKenney
2005-03-23 4:48 ` [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-01 Paul E. McKenney
2005-03-23 6:21 ` Ingo Molnar
2005-03-22 8:59 ` Ingo Molnar
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