From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>,
Ingo Molnar <mingo@elte.hu>, Paul Mackerras <paulus@samba.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: Lock dependency based tree report in perf lock
Date: Mon, 01 Feb 2010 09:25:04 +0100 [thread overview]
Message-ID: <1265012704.24455.80.camel@laptop> (raw)
In-Reply-To: <20100130185736.GC5675@nowhere>
On Sat, 2010-01-30 at 19:57 +0100, Frederic Weisbecker wrote:
> On Sat, Jan 30, 2010 at 09:46:28AM +0100, Peter Zijlstra wrote:
> > On Sat, 2010-01-30 at 00:17 +0100, Frederic Weisbecker wrote:
> > >
> > >
> > > Anyway, that's just an idea, not trivial I must admit.
> >
> > lockdep actually collects all this information, so writing it out isn't
> > too hard.
>
>
>
> Lockdep collects the theorical dependencies but not the practical
> scenarios.
>
> Say B and C depend on A, you'll get:
>
> A
> / \
> B C
>
> But nothing can tell you that if A is taken, B and C will always
> be taken. You may have different scenarios based on this dependency,
> which is not something that lockdep logs, right?
Right. But we keep track of the full held lock stack, which is what was
requested.
next prev parent reply other threads:[~2010-02-01 8:25 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-29 23:17 Lock dependency based tree report in perf lock Frederic Weisbecker
2010-01-30 8:46 ` Peter Zijlstra
2010-01-30 18:57 ` Frederic Weisbecker
2010-02-01 8:25 ` Peter Zijlstra [this message]
2010-02-01 17:48 ` Frederic Weisbecker
2010-02-01 1:23 ` Frederic Weisbecker
2010-02-01 9:21 ` Peter Zijlstra
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