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Subject: RE: "double" hpet clocksource && hard freeze [bisected]
Date: Fri, 24 Aug 2007 09:04:22 -0700
Message-ID: <617E1C2C70743745A92448908E030B2A023EB8C4@scsmsx411.amr.corp.intel.com>
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Thread-Topic: "double" hpet clocksource && hard freeze [bisected]
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References: <20070823222115.122a37ca@localhost><617E1C2C70743745A92448908E030B2A023EB2E1@scsmsx411.amr.corp.intel.com><1187903135.6024.18.camel@localhost.localdomain><1187905306.6024.24.camel@localhost.localdomain><20070824124631.GF10594@localhost> <20070824152745.56214a24@localhost>
From: "Luck, Tony" <tony.luck@intel.com>
To: "Paolo Ornati" <ornati@fastwebnet.it>, "Bob Picco" <bob.picco@hp.com>
Cc: "john stultz" <johnstul@us.ibm.com>,
       "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
       "Bob Picco" <bob.picco@hp.com>
Sender: linux-kernel-owner@vger.kernel.org
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> > Prevent duplicate names being registered with clocksource. This also
> > eliminates the duplication of hpet clock registration when the arch
> > uses the hpet timer and the hpet driver does too. The patch was
> > compile and link tested.
>
> This one works too.

It is good to avoid registering two clocksources with the same name, but
the fix might be a bit more fragile than the eariler one that temporarily
marked the drivers/char/hpet.c one as CONFIG_IA64 only.  Given that the
hang went away when you applied the earlier patch, I conclude that the
drivers/char/hpet.c code is the one that got selected when you had two
"hpet" entries ... and that there is something wrong with that code that
doesn't work right on x86_64.  The fix to prevent registering a duplicate
name is presumably working for you simply because arch/x86_64/kernel/hpet.c
happens to get there first with its "hpet", so the drivers/char/hpet.c one
is dropped.  If something changed that reversed the order of these registrations,
then you'd get the "hpet" clocksource that results in a hang.

-Tony
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