From: Ingo Molnar <mingo@elte.hu>
To: Dave Jones <davej@redhat.com>,
linux-kernel@vger.kernel.org, 76306.1226@compuserve.com
Subject: Re: + spinlock_debug-dont-recompute-jiffies_per_loop.patch added to -mm tree
Date: Tue, 25 Jul 2006 22:43:06 +0200 [thread overview]
Message-ID: <20060725204306.GA22547@elte.hu> (raw)
In-Reply-To: <20060725204228.GE13829@redhat.com>
* Dave Jones <davej@redhat.com> wrote:
> > iteration limit, gets recomputed every time. Caching it explicitly
> > prevents that.
>
> What is the purpose of those __delays being there at all ? Seems odd
> to be waiting that long when the spinlock could become available a lot
> sooner. (These also make spinlock debug really painful on boxes with
> huge numbers of CPUs).
the debug code has to figure out when to trigger a deadlock warning
message. If we are looping in a deadlock with irqs disabled on all CPUs,
there's nothing that advances jiffies. The TSC is not reliable. The
thing that remains is to use __delay(1). We could calibrate the loop
separately perhaps?
Ingo
next prev parent reply other threads:[~2006-07-25 20:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200607251910.k6PJASfo006168@shell0.pdx.osdl.net>
2006-07-25 20:42 ` Dave Jones
2006-07-25 20:43 ` Ingo Molnar [this message]
2006-07-27 5:53 Chuck Ebbert
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