From: Keith Owens <kaos@ocs.com.au>
To: george anzinger <george@mvista.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: How should we do a 64-bit jiffies?
Date: Tue, 23 Oct 2001 15:10:48 +1000 [thread overview]
Message-ID: <1164.1003813848@ocs3.intra.ocs.com.au> (raw)
In-Reply-To: Your message of "Mon, 22 Oct 2001 08:12:24 MST." <3BD43758.32646D49@mvista.com>
On Mon, 22 Oct 2001 08:12:24 -0700,
george anzinger <george@mvista.com> wrote:
>I am working on POSIX timers where there is defined a CLOCK_MONOTONIC.
>The most reasonable implementation of this clock is that it is "uptime"
>or jiffies. The problem is that it is most definitely not MONOTONIC
>when it rolls back to 0 :( Thus the need for 64-bits.
If you want to leave existing kernel code alone so it still uses 32 bit
jiffies, just maintain a separate high order 32 bit field which is only
used by the code that really needs it. On 32 bit machines, the jiffie
code does
old_jiffies = jiffies++;
if (jiffies < old_jiffies)
++high_jiffies;
You will need a spin lock around that on 32 bit systems, but that is
true for anything that tries to do 64 bit counter updates on a 32 bit
system. None of your suggestions will work on ix86, it does not
support atomic updates on 64 bit fields in hardware.
next prev parent reply other threads:[~2001-10-23 5:11 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-10-22 15:12 How should we do a 64-bit jiffies? george anzinger
2001-10-23 5:10 ` Keith Owens [this message]
2001-10-23 6:05 ` Brian Gerst
2001-10-23 6:23 ` Keith Owens
2001-10-23 8:03 ` george anzinger
2001-10-23 15:45 ` Linus Torvalds
2001-10-26 20:59 ` george anzinger
[not found] ` <200110231545.f9NFjgg01377@penguin.transmeta.com>
2002-05-10 21:35 ` 64-bit jiffies, a better solution george anzinger
2002-05-10 21:52 ` Linus Torvalds
2002-05-10 22:36 ` george anzinger
2002-05-10 22:40 ` Linus Torvalds
2002-05-11 0:42 ` 64-bit jiffies, a better solution take 2 george anzinger
2002-05-11 8:29 ` Russell King
2002-05-11 15:01 ` george anzinger
2002-05-11 16:10 ` Russell King
2002-05-11 17:31 ` george anzinger
2002-05-11 17:37 ` Linus Torvalds
2002-05-11 18:11 ` Russell King
2002-05-11 23:38 ` Keith Owens
2002-05-12 0:01 ` Russell King
2002-05-12 0:31 ` Keith Owens
2002-05-12 8:12 ` george anzinger
[not found] ` <3CDD6DA1.7B259EF1@mvista.com>
[not found] ` <20020511201748.G1574@flint.arm.linux.org.uk>
2002-05-12 8:03 ` 64-bit jiffies, a better solution take 2 (Fix ARM) george anzinger
2002-05-11 16:41 ` 64-bit jiffies, a better solution take 2 Daniel Jacobowitz
2002-05-13 11:09 ` 64-bit jiffies, a better solution Maciej W. Rozycki
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