From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Wed, 09 Apr 2003 17:53:20 +0000 Subject: Re: [Linux-ia64] [patch] 2.4 timer_interrupt/gettimeoffset machvec Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Tue, 8 Apr 2003 14:49:25 -0700, Jesse Barnes said: >> The motivation for changing timer_interrupt() seems suspect to me. >> The timer interupt is generated PER CPU, so there is no drift issue at >> all (in fact, we intentionally _skew_ things at boot time to reduce >> the likelihood of getting all timer interrupts at the same time). Jesse> The problem is that we want high resolution gettimeofday, which means Jesse> that we need to know how long its been since wall time was updated Jesse> when gettimeoffset is called. We do that right now by snapshoting the Jesse> RTC in timer_interrupt... Clearly you need to establish the relationship between the external clock and time-of-day somewhere, but I'm not so sure this should be done in the arch-specific timer interrupt handler. I suspect you really want to do it where the time-of-day gets updated. Also, I think this should be treated much more as a driver issue rather than a platform-issue (suppose someone plugged in an adapter card providing a low-latency, atomic accurracy & high precision lock, you'd presumably want to be able to use that card in favor of whatever other hardware might be there. --david