Messages in this thread | | | Date | Wed, 07 Nov 2001 16:44:26 -0800 (PST) | Subject | Re: [PATCH] net/ipv4/*, net/core/neighbour.c jiffies cleanup | From | "David S. Miller" <> |
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From: Andreas Dilger <adilger@turbolabs.com> Date: Wed, 7 Nov 2001 17:36:27 -0700
No, only a limited number of them cast to a signed value, which means that a large number of them get the comparison wrong in the case of jiffies wrap (where the difference is a large unsigned value, and not a small negative number).
Why do they these cases that are actually in the code need to cast to a signed value to get a correct answer? They are not like your example.
Almost all of these cases are:
(jiffies - SOME_VALUE_KNOWN_TO_BE_IN_THE_PAST) > 5 * HZ
So you say if we don't cast to signed, this won't get it right on wrap-around? I disagree, let's say "long" is 32-bits and jiffies wrapped around to "0x2" and SOME_VALUE... is 0xfffffff8. The subtraction above yields 10, and that is what we want.
Please show me a bad case where casting to signed is necessary.
I actually ran through the tree the other night myself starting to convert these things, then I noticed that I couldn't even convince myself that the code was incorrect.
Franks a lot, David S. Miller davem@redhat.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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