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/
This archive was generated by hypermail 2b29 : Wed Nov 07 2001 - 21:00:37 EST