From: "Paul E. McKenney" <paulmck@us.ibm.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Dipankar Sarma <dipankar@in.ibm.com>,
Sven Dietrich <sdietrich@mvista.com>,
Daniel Walker <dwalker@mvista.com>, Andrew Morton <akpm@osdl.org>,
linux-kernel@vger.kernel.org, abatyrshin@ru.mvista.com,
amakarov@ru.mvista.com, emints@ru.mvista.com,
ext-rt-dev@mvista.com, hzhang@ch.mvista.com, yyang@ch.mvista.com,
"Witold. Jaworski@Unibw-Muenchen. De"
<witold.jaworski@unibw-muenchen.de>,
arnd.heursch@unibw-muenchen.de
Subject: Re: [ANNOUNCE] Linux 2.6 Real Time Kernel
Date: Fri, 15 Oct 2004 09:40:39 -0700 [thread overview]
Message-ID: <20041015164039.GA1265@us.ibm.com> (raw)
In-Reply-To: <20041015154542.GA8257@elte.hu>
On Fri, Oct 15, 2004 at 05:45:42PM +0200, Ingo Molnar wrote:
>
> * Paul E. McKenney <paulmck@us.ibm.com> wrote:
>
> > One caution (which you are no doubt already aware of) -- if an RCU
> > algorithm that reads (rcu_read_lock()/rcu_read_unlock()) in process
> > context and updates in softirq/bh/irq context, you can see deadlocks.
>
> yeah - but in the PREEMPT_REALTIME kernel there are simply no irq or
> softirq contexts in process contexts - everything is a task. So
> everything can (and does) block.
OK, am probably confused, but I thought that the whole point of your
PREEMPT_REALTIME implementation of rcu_read_lock_rt() was to enable
preemption in the RCU read-side critical section. If this is indeed
the case, then it looks to me like code that would run in softirq/bh/irq
context in a kernel compiled non-PREEMPT_REALTIME could now run during
the time that a code path running under rcu_read_lock_rt() was preempted.
If so, then the kernel can end up freeing a data item that the preempted
RCU read-side critical section is still referencing.
OK, so what am I missing here?
Thanx, Paul
next prev parent reply other threads:[~2004-10-15 16:46 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-09 5:59 [ANNOUNCE] Linux 2.6 Real Time Kernel Sven-Thorsten Dietrich
2004-10-09 6:40 ` Lee Revell
2004-10-09 7:33 ` Daniel Walker
2004-10-09 7:42 ` Lee Revell
2004-10-09 23:40 ` Matthias Urlichs
2004-10-09 8:52 ` Lee Revell
2004-10-09 23:20 ` Dave Hansen
2004-10-09 23:24 ` Lee Revell
2004-10-09 10:51 ` Måns Rullgård
2004-10-09 13:15 ` Måns Rullgård
2004-10-09 21:20 ` Lee Revell
2004-10-09 21:35 ` Måns Rullgård
2004-10-09 21:37 ` Lee Revell
2004-10-09 21:45 ` Måns Rullgård
2004-10-09 21:55 ` Lee Revell
2004-10-09 22:21 ` Måns Rullgård
2004-10-09 23:52 ` Lee Revell
2004-10-10 0:05 ` Måns Rullgård
2004-10-10 0:45 ` Lee Revell
2004-10-10 1:05 ` Måns Rullgård
2004-10-10 1:09 ` Lee Revell
2004-10-10 0:43 ` Micha Feigin
2004-10-10 1:08 ` Måns Rullgård
2004-10-09 17:41 ` Karim Yaghmour
2004-10-09 18:30 ` Lee Revell
2004-10-09 21:26 ` stefan.eletzhofer
2004-10-09 19:30 ` Lee Revell
2004-10-09 19:38 ` Måns Rullgård
2004-10-09 21:38 ` stefan.eletzhofer
2004-10-09 19:47 ` Lee Revell
2004-10-09 20:11 ` Karim Yaghmour
2004-10-09 20:14 ` Lee Revell
2004-10-09 20:53 ` Karim Yaghmour
2004-10-09 20:59 ` Lee Revell
2004-10-09 20:20 ` Robert Love
2004-10-09 20:25 ` Lee Revell
2004-10-10 1:15 ` Lee Revell
2004-10-10 8:46 ` Ingo Molnar
2004-10-10 19:41 ` Daniel Walker
2004-10-10 19:46 ` Ingo Molnar
2004-10-10 21:20 ` Andrew Morton
2004-10-10 21:59 ` Ingo Molnar
2004-10-11 17:53 ` Daniel Walker
2004-10-11 20:49 ` Ingo Molnar
2004-10-11 21:44 ` Sven Dietrich
2004-10-11 21:54 ` Ingo Molnar
2004-10-11 23:05 ` Sven Dietrich
2004-10-12 5:50 ` Ingo Molnar
2004-10-14 5:09 ` Dipankar Sarma
2004-10-14 7:18 ` Ingo Molnar
2004-10-15 14:59 ` Paul E. McKenney
2004-10-15 15:45 ` Ingo Molnar
2004-10-15 16:40 ` Paul E. McKenney [this message]
2004-10-15 16:45 ` Paul E. McKenney
2004-10-17 17:12 ` Ingo Molnar
2004-10-12 18:50 ` Daniel Walker
2004-10-12 19:46 ` [Ext-rt-dev] " Thomas Gleixner
2004-10-12 20:31 ` Sven Dietrich
2004-10-12 20:37 ` Thomas Gleixner
2004-10-13 0:30 ` George Anzinger
2004-10-12 21:12 ` Bill Huey
2004-10-12 21:24 ` Bill Huey
2004-10-12 21:32 ` Thomas Gleixner
2004-10-12 23:13 ` Bill Huey
2004-10-12 21:41 ` Sven Dietrich
2004-10-12 22:57 ` Bill Huey
2004-10-12 23:17 ` Adam Heath
2004-10-12 23:36 ` Lee Revell
2004-10-12 23:25 ` Thomas Gleixner
2004-10-13 2:02 ` K.R. Foley
2004-10-13 13:39 ` Martijn Sipkema
2004-10-13 13:26 ` La Monte H.P. Yarroll
2004-10-13 15:04 ` Martijn Sipkema
2004-10-13 14:55 ` Kurt Wall
2004-10-13 14:52 ` Christoph Hellwig
2004-10-13 15:56 ` Lee Revell
2004-10-13 16:13 ` Robert Love
2004-10-13 17:14 ` Martijn Sipkema
2004-10-13 3:55 ` Bill Huey
2004-10-12 22:00 ` Thomas Gleixner
2004-10-12 22:36 ` Bill Huey
2004-10-12 23:10 ` Thomas Gleixner
2004-10-12 23:33 ` Bill Huey
2004-10-12 23:37 ` Thomas Gleixner
2004-10-12 23:52 ` Bill Huey
2004-10-13 0:59 ` Valdis.Kletnieks
2004-10-10 12:21 ` John Richard Moser
2004-10-10 17:26 ` Lee Revell
2004-10-10 18:45 ` John Richard Moser
2004-10-10 20:20 ` Ingo Molnar
2004-10-10 20:44 ` John Richard Moser
2004-10-10 17:29 ` Daniel Walker
-- strict thread matches above, loose matches on Subject: below --
2004-10-09 11:38 John Hedditch
2004-10-09 22:54 Sven Dietrich
2004-10-11 15:28 Vadim Lebedev
2004-10-11 15:50 ` Eugeny S. Mints
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