Date: Mon, 24 Jul 2000 20:55:33 -0600 From: Chuck Paterson <cp@bsdi.com> To: Greg Lehey <grog@lemis.com> Cc: freebsd-smp@freebsd.org Subject: com interrupts and heavy weight threads Message-ID: <200007250255.UAA02299@berserker.bsdi.com>
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Greg, Concerning the discussion a while ago on the benefits of having com and other such interrupts always run in a borrowed context. I do agree that you will want to end up running these interrupts always in a borrowed context. But, you may want to actually run these as heavy weight interrupts when you first start. Here's the deal. I don't think this was explicitly mentioned but if you use a borrowed context you have to get the low level com driver locked up (mutices installed and working) in order to boot at all. There isn't a half way step of running this code under the Giant lock. You wouldn't want/need to change the driver structure at all during this phase, just get the stuff to run. If I were doing this I think I would go ahead and lock up the com driver, but until I looked at it some I'm not sure. This is more to make sure you are aware of the issue than to influence the decision you arrive at. Chuck To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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