Date: Fri, 11 Jan 2002 14:45:38 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: Skye Poier <skye@ffwd.cx> Cc: FreeBSD 31337 H4X0RZ <freebsd-hackers@freebsd.org> Subject: Re: Possible problem with timeouts? Message-ID: <3C3F6B12.452655E3@mindspring.com> References: <20020111132615.A36583@ffwd.cx>
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Skye Poier wrote: > It seems that it is possible to call untimeout and then have your timer > called immediately thereafter. However, we haven't actually seen this in > practice, this is a theoretical bug. If this is indeed the case, it will > break lots of our code (misunderstood semantics..) Yes, this can happen. No, it doesn't break anything. Timeouts wake on an address, and if your code is no longer sleeping on it, then it doesn't matter. The only complex case is the case where you have multiple things sleeping ont he same address, and you expect "wake one" instead of "wakeup" behaviour (your expectation is incorrect, if this is the case). If you are using a non-generic callout, then it's possible, if you do not do proper guarding of your code, to have a callout called at the wrong priority. This will only happen if you untimeout at a priority different than the priority of the code being awoken (coding error). Otherwise, the fact of the priority level blocking against itself should be enough to save you. Arew you observing an error in this regard? > Now, its possible that this has been fixed since we took a snapshot of > -current way back around Feb/Mar 2001. Wow. That's *really* old. All bets are off, since that is incredibly unknown-to-the-rest-of-us code you are running, there... > If anyone has some insight into this it would be much appreciated. I > have a second question around softclock but I'll save it for later.. If it's about the ineffeciencies in the fixed intervals for a large number of simultaneous TCP connections, we already know... -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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