From: Ingo Molnar <mingo@elte.hu>
To: john cooper <john.cooper@timesys.com>
Cc: Mark_H_Johnson@raytheon.com,
Karsten Wiese <annabellesgarden@yahoo.de>,
Bill Huey <bhuey@lnxw.com>, Adam Heath <doogie@debian.org>,
"K.R. Foley" <kr@cybsft.com>,
linux-kernel@vger.kernel.org,
Florian Schmidt <mista.tapas@gmx.net>,
Fernando Pablo Lopez-Lezcano <nando@ccrma.Stanford.EDU>,
Lee Revell <rlrevell@joe-job.com>,
Rui Nuno Capela <rncbc@rncbc.org>,
Thomas Gleixner <tglx@linutronix.de>,
Michal Schmidt <xschmi00@stud.feec.vutbr.cz>
Subject: Re: [patch] Real-Time Preemption, -RT-2.6.10-rc1-mm2-V0.7.1
Date: Thu, 4 Nov 2004 20:44:16 +0100 [thread overview]
Message-ID: <20041104194416.GC10107@elte.hu> (raw)
In-Reply-To: <418A7BFB.6020501@timesys.com>
* john cooper <john.cooper@timesys.com> wrote:
> > plus there's the 'priority inheritance dependency-chain closure' bug
> > noticed by John Cooper - that should only affect the latency of RT
> > tasks though.
>
> This is a fairly gnarly problem to address. The obvious solution is
> to hold spinlocks in the mutexes as the dependency tree is atomically
> traversed. However this will deadlock under MP due to the
> unpredictable order of mutexes traversed. If the dependency chain is
> not traversed (and semantics applied) atomically, races exist which
> cause promotion decisions to be made on [now] stale data.
is the order of locks in the dependency chain really unpredictable? If
two chain walkers get two locks in opposite order, doesnt that mean that
the lock ordering (as attempted by the blocked tasks) is deadlock-prone
already? I.e. this scenario should not happen.
Ingo
next prev parent reply other threads:[~2004-11-04 19:46 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-11-04 16:22 [patch] Real-Time Preemption, -RT-2.6.10-rc1-mm2-V0.7.1 Mark_H_Johnson
2004-11-04 16:30 ` Ingo Molnar
2004-11-04 16:32 ` Ingo Molnar
2004-11-04 18:59 ` john cooper
2004-11-04 19:44 ` Ingo Molnar [this message]
2004-11-04 23:25 ` john cooper
2004-11-05 21:42 ` Scott Wood
2004-11-05 22:36 ` Bill Huey
2004-11-08 14:35 ` Esben Nielsen
2004-11-08 15:42 ` Ingo Molnar
2004-11-08 22:47 ` Bill Huey
2004-11-06 7:42 ` Ingo Molnar
-- strict thread matches above, loose matches on Subject: below --
2004-11-04 19:39 Mark_H_Johnson
2004-11-04 19:52 ` Ingo Molnar
2004-11-04 17:52 Mark_H_Johnson
2004-11-04 16:53 Mark_H_Johnson
2004-11-04 16:04 Mark_H_Johnson
2004-11-04 16:13 ` Ingo Molnar
2004-11-04 16:17 ` Ingo Molnar
2004-11-04 15:02 Mark_H_Johnson
2004-11-04 15:16 ` Ingo Molnar
2004-11-04 15:19 ` Ingo Molnar
2004-11-03 20:40 Mark_H_Johnson
2004-11-03 18:24 Mark_H_Johnson
2004-10-18 14:50 [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U5 Ingo Molnar
2004-10-19 12:46 ` [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U6 Ingo Molnar
2004-10-19 18:00 ` [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U7 Ingo Molnar
2004-10-20 9:45 ` [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U8 Ingo Molnar
2004-10-21 13:27 ` [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U9 Ingo Molnar
2004-10-22 13:35 ` [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U9.3 Ingo Molnar
2004-10-22 15:50 ` [patch] Real-Time Preemption, -RT-2.6.9-mm1-U10 Ingo Molnar
2004-10-22 17:56 ` [patch] Real-Time Preemption, -RT-2.6.9-mm1-U10.2 Ingo Molnar
2004-10-25 10:40 ` [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0 Ingo Molnar
2004-10-27 0:15 ` [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.3 Ingo Molnar
2004-11-03 10:58 ` [patch] Real-Time Preemption, -RT-2.6.10-rc1-mm2-V0.7.1 Ingo Molnar
2004-11-03 13:44 ` Lorenzo Allegrucci
2004-11-03 13:46 ` Ingo Molnar
2004-11-03 17:53 ` Lorenzo Allegrucci
2004-11-03 20:41 ` Lorenzo Allegrucci
2004-11-03 20:43 ` Ingo Molnar
2004-11-03 21:05 ` Lorenzo Allegrucci
2004-11-03 19:33 ` john cooper
2004-11-03 23:03 ` Magnus Naeslund(t)
2004-11-04 6:56 ` Ingo Molnar
2004-11-04 19:34 ` Gunther Persoons
2004-11-04 20:31 ` Chris Friesen
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