From: Mike Galbraith <bitbucket@online.de>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Manfred Spraul <manfred@colorfullife.com>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH RT] rt,ipc,sem: fix -rt livelock
Date: Fri, 13 Sep 2013 05:20:21 +0200 [thread overview]
Message-ID: <1379042421.5455.47.camel@marge.simpson.net> (raw)
In-Reply-To: <20130912151547.389673d2@gandalf.local.home>
On Thu, 2013-09-12 at 15:15 -0400, Steven Rostedt wrote:
> On Thu, 12 Sep 2013 09:40:28 +0200
> Mike Galbraith <bitbucket@online.de> wrote:
>
>
> > If maintainers are interested, I can add that and clean up hammer marks
> > so it can be applied in lieu of the existing rt wakeup patch instead of
> > being crammed in on top of it, or they can trivially do that themselves,
> > both options presuming your (implied) approval.
> >
>
> Mike,
>
> What's the final patch for this?
Both loop removal patch or something like it (but prettier), and
Manfred's wakeup scheme to prevent the locked array lock being being
seen and reacted to by wakees, who can then contend on that lock,
defeating the whole purpose for a while.
> Could you post another one with what you believe is the correct fix.
As noted, I _think_ they're both needed. Manfred's wakeup scheme cures
a trigger, but not the bug methinks (non-deterministic trylock loop).
Would be nice if it turned out that it cured all possible livelocks, but
I don't think it does. Even if it did, crawling over a large array
always taking and releasing every lock will suck, which is why I did the
look at it before taking it thing. That ain't pretty, but it's less
painful.
-Mike
next prev parent reply other threads:[~2013-09-13 3:20 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-19 21:33 [PATCH RT 0/3] hwlat-detector: Have it actually find hardware latency Steven Rostedt
2013-08-19 21:33 ` [PATCH RT 1/3] hwlat-detector: Update hwlat_detector to add outer loop detection Steven Rostedt
2013-08-19 21:33 ` [PATCH RT 2/3] hwlat-detector: Use trace_clock_local if available Steven Rostedt
2013-08-19 21:33 ` [PATCH RT 3/3] hwlat-detector: Use thread instead of stop machine Steven Rostedt
2013-08-21 15:59 ` [PATCH RT 0/3] hwlat-detector: Have it actually find hardware latency Sebastian Andrzej Siewior
2013-08-30 5:57 ` [PATCH RT] hwlat-detector: Don't ignore threshold module parameter Mike Galbraith
2013-08-30 14:39 ` [PATCH RT] rt,ipc,sem: fix -rt livelock Mike Galbraith
2013-08-31 5:27 ` Mike Galbraith
2013-09-06 7:08 ` Mike Galbraith
2013-09-10 6:30 ` Mike Galbraith
2013-09-11 14:03 ` Manfred Spraul
2013-09-12 7:40 ` Mike Galbraith
2013-09-12 19:15 ` Steven Rostedt
2013-09-13 3:20 ` Mike Galbraith [this message]
2013-09-13 3:33 ` Steven Rostedt
2013-09-13 4:48 ` Mike Galbraith
2013-09-13 4:36 ` Mike Galbraith
2013-09-13 12:56 ` Mike Galbraith
2013-09-12 18:23 ` [PATCH RT] hwlat-detector: Don't ignore threshold module parameter Steven Rostedt
2013-10-04 10:30 ` Sebastian Andrzej Siewior
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