From: Chris Metcalf <cmetcalf@tilera.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] arch/tile: new multi-core architecture for Linux
Date: Wed, 26 May 2010 12:22:33 -0400 [thread overview]
Message-ID: <4BFD4AC9.6080602@tilera.com> (raw)
In-Reply-To: <alpine.LFD.2.00.1005252129441.2948@localhost.localdomain>
On 5/25/2010 4:12 PM, Thomas Gleixner wrote:
> +unsigned long long sched_clock(void)
> +{
> + u64 cycles;
> + u32 cyc_hi, cyc_lo;
> +
> + if (unlikely(cyc2ns_mult == 0))
> + setup_clock();
>
> Please initialize stuff _before_ it is called the first time and not
> at some arbitrary point conditionally in a hotpath.
>
Looking more closely at this, the reason for this lazy initialization
was that sched_clock() can be called from lockdep_init(), which runs way
before any tasteful architecture-specific initialization can happen.
Perhaps the correct model is that during the early stages of boot, we
are happy to shift by zero, multiply by zero, and claim the time is zero :-)
--
Chris Metcalf, Tilera Corp.
http://www.tilera.com
next prev parent reply other threads:[~2010-05-26 16:22 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-20 5:43 [PATCH] arch/tile: new multi-core architecture for Linux Chris Metcalf
2010-05-20 8:04 ` Barry Song
2010-05-20 14:32 ` Linus Torvalds
2010-05-20 19:10 ` Chris Metcalf
2010-05-21 4:52 ` Barry Song
2010-05-21 15:13 ` Chris Metcalf
2010-05-20 19:12 ` [PATCH] generic: make lowmem_page_address() use PFN_PHYS() for improved portability Chris Metcalf
2010-05-22 4:05 ` [PATCH] arch/tile: new multi-core architecture for Linux Chris Metcalf
2010-05-23 22:08 ` Arnd Bergmann
2010-05-24 15:29 ` Chris Metcalf
2010-05-24 18:53 ` Arnd Bergmann
2010-05-24 21:29 ` Chris Metcalf
2010-05-25 13:54 ` Chris Metcalf
2010-05-25 15:03 ` Arnd Bergmann
2010-05-25 15:13 ` Chris Metcalf
2010-05-25 15:30 ` Arnd Bergmann
2010-05-26 2:44 ` liqin.chen
2010-05-26 13:45 ` Chris Metcalf
[not found] ` <4BFBE005.2070500@tilera.com>
[not found] ` <201005251721.23782.arnd@arndb.de>
2010-05-26 23:05 ` Chris Metcalf
2010-05-26 5:02 ` Paul Mundt
2010-05-25 21:45 ` Arnd Bergmann
2010-05-27 0:58 ` Chris Metcalf
2010-05-27 8:41 ` Arnd Bergmann
2010-05-27 13:30 ` Chris Metcalf
2010-05-27 13:41 ` Geert Uytterhoeven
2010-05-27 13:48 ` Paul Mundt
2010-05-27 14:11 ` Arnd Bergmann
2010-05-27 14:35 ` Chris Metcalf
2010-05-27 15:02 ` Arnd Bergmann
2010-05-27 15:04 ` Chris Metcalf
2010-05-27 15:20 ` Arnd Bergmann
2010-05-27 14:52 ` Marc Gauthier
2010-05-28 17:58 ` Chris Metcalf
2010-05-27 15:03 ` Chris Metcalf
2010-05-27 20:34 ` Jamie Lokier
2010-05-27 20:53 ` Arnd Bergmann
2010-05-28 16:45 ` Chris Metcalf
2010-05-28 17:16 ` Arnd Bergmann
2010-05-28 17:28 ` Chris Metcalf
2011-05-16 18:23 ` [PATCH] arch/tile: support signal "exception-trace" hook Chris Metcalf
2011-05-18 18:14 ` Chris Metcalf
2011-05-17 20:26 ` [PATCH] arch/tile: add /proc/tile, /proc/sys/tile, and a sysfs cpu attribute Chris Metcalf
2011-05-19 13:41 ` Arnd Bergmann
2011-05-19 15:12 ` Chris Metcalf
2011-05-19 15:22 ` Arnd Bergmann
2011-05-20 14:26 ` Chris Metcalf
2011-05-20 14:37 ` Arnd Bergmann
2011-05-20 15:00 ` Chris Metcalf
2011-05-20 15:13 ` Arnd Bergmann
2011-05-20 19:59 ` Arnd Bergmann
2011-05-25 19:18 ` Chris Metcalf
2011-05-25 20:20 ` Arnd Bergmann
2011-05-25 20:31 ` Chris Metcalf
2011-05-25 20:34 ` Arnd Bergmann
2011-05-24 15:38 ` Arnd Bergmann
2011-05-26 16:40 ` [PATCH v2] arch/tile: more /proc and /sys file support Chris Metcalf
2011-05-27 14:23 ` Arnd Bergmann
2010-05-24 20:22 ` [PATCH] arch/tile: new multi-core architecture for Linux Sam Ravnborg
2010-05-24 21:30 ` Chris Metcalf
2010-05-25 5:02 ` Sam Ravnborg
2010-05-25 20:12 ` Thomas Gleixner
2010-05-26 1:57 ` Chris Metcalf
2010-05-26 16:22 ` Chris Metcalf [this message]
2010-05-26 17:09 ` Arnd Bergmann
2010-05-29 3:01 ` [PATCH 1/8] Fix up the "generic" unistd.h ABI to be more useful Chris Metcalf
2010-05-29 3:09 ` [PATCH 2/8] arch/tile: infrastructure and configuration-related files Chris Metcalf
2010-05-31 7:47 ` Paul Mundt
2010-06-03 17:54 ` Chris Metcalf
2010-05-29 3:10 ` [PATCH 3/8] arch/tile: header files for the Tile architecture Chris Metcalf
2010-05-31 2:58 ` FUJITA Tomonori
2010-06-03 21:32 ` [PATCH] arch/tile: respond to reviews of the second code submission Chris Metcalf
2010-06-04 0:50 ` Paul Mundt
2010-06-04 1:31 ` FUJITA Tomonori
2010-06-07 5:25 ` FUJITA Tomonori
2010-05-29 3:10 ` [PATCH 4/8] arch/tile: core kernel/ code Chris Metcalf
2010-05-31 2:58 ` FUJITA Tomonori
2010-05-29 3:11 ` [PATCH 5/8] arch/tile: the kernel/tile-desc_32.c file Chris Metcalf
2010-05-29 3:13 ` [PATCH 6/8] arch/tile: the mm/ directory Chris Metcalf
2010-05-29 3:16 ` [PATCH 7/8] arch/tile: lib/ directory Chris Metcalf
2010-05-29 3:17 ` [PATCH 8/8] arch/tile: hypervisor console driver Chris Metcalf
[not found] ` <dVZMmBu$KHA.5388@exchange1.tad.internal.tilera.com>
2010-05-29 3:20 ` [PATCH 0/8] revised patch for arch/tile/ support Chris Metcalf
2010-05-29 3:20 ` Chris Metcalf
2010-05-29 11:29 ` Arnd Bergmann
2010-06-03 20:40 ` Arnd Bergmann
2010-06-03 21:48 ` Chris Metcalf
2010-06-04 21:32 ` Chris Metcalf
2010-06-05 12:56 ` Stephen Rothwell
2010-06-05 13:30 ` Chris Metcalf
2010-06-05 14:10 ` Stephen Rothwell
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