linux-kernel - Re: [discuss] Re: 2.6.19-rc5: known regressions (v3)

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Message-ID: <17756.17330.974883.486535@alkaid.it.uu.se>
Date:	Thu, 16 Nov 2006 11:55:46 +0100
From:	Mikael Pettersson <mikpe@...uu.se>
To:	Andrew Morton <akpm@...l.org>
Cc:	ebiederm@...ssion.com (Eric W. Biederman), Andi Kleen <ak@...e.de>,
	Linus Torvalds <torvalds@...l.org>, discuss@...-64.org,
	William Cohen <wcohen@...hat.com>,
	Komuro <komurojun-mbn@...ty.com>,
	Ernst Herzberg <earny@...4u.de>,
	Andre Noll <maan@...temlinux.org>,
	oprofile-list@...ts.sourceforge.net,
	Jens Axboe <jens.axboe@...cle.com>,
	linux-usb-devel@...ts.sourceforge.net, phil.el@...adoo.fr,
	Adrian Bunk <bunk@...sta.de>, Ingo Molnar <mingo@...hat.com>,
	Alan Stern <stern@...land.harvard.edu>,
	linux-pci@...ey.karlin.mff.cuni.cz,
	Stephen Hemminger <shemminger@...l.org>,
	Prakash Punnoor <prakash@...noor.de>,
	Len Brown <len.brown@...el.com>,
	Alex Romosan <romosan@...orax.lbl.gov>, gregkh@...e.de,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrey Borzenkov <arvidjaar@...l.ru>
Subject: Re: [discuss] Re: 2.6.19-rc5: known regressions (v3)

Andrew Morton writes:
 > Surely the appropriate behaviour is to allow oprofile to steal the NMI and
 > to then put the NMI back to doing the watchdog thing after oprofile has
 > finished with it.

Which is _exactly_ what pre-2.6.19-rc1 kernels did. I implemented
the in-kernel API allowing real performance counter drivers like
oprofile (and perfctr) to claim the HW from the NMI watchdog,
do their work, and then release it which resumed the watchdog.

Note that oprofile (and perfctr) didn't do anything behind the
NMI watchdog's back. They went via the API. Nothing dodgy going on.
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