Date: Fri, 9 Feb 2001 10:24:50 -0500 From: Clark Jarvis <cjarvis@VCI.com> To: net@freebsd.org Subject: RE: potential infinite loop in network device drivers Message-ID: <76AE66BFB2FBD211A30B0008C7DF6C2D01718451@exchange.vci.com>
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> it occurs to me that there is a potential infinite loop in > most if not all ethernet drivers. Basically, on a > receive interrupt, such drivers loop around the status word > until the receive queue is drained. > > If the body of the loop takes approx the same as > the packet interarrival time, you might end up stuck in > the loop forever (and typically holding locks or with most > interrupts masked off). > > I would suggest that we slightly redesign such loops so that > we limit the amt of time spent in them. This probably > affects only 100M/1G interfaces these days, but still... I remember thinking about this at one point, and deciding that it wasn't worth working around. The problem was that if you leave before cleaning up all the interrupt conditions, you'll just get another interrupt and be right back almost immediately anyway. Yeah, you get a little window for other things to happen, but not much, and you add overhead, slowing down what is obviously a busy device. It'll still be interesting to read the papers Garrett mentioned... -- Clark ********************************************************************** This email, and any files transmitted with it, are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please advise ismail@vci.com. ********************************************************************** To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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