Aren't you forgetting an important part? The part at the end where the source code is shown, that Linus didn't actually make the change, just made a comment saying that it would be nice if he could.
That part showed up after that issue of KT came out; I don't know whether it showed up after I checked it earlier today or not (I'd assumed that issues of KT are invariant after publication, and I saw that issue before the note was added).
Some stuff in the FreeBSD archive indicates that they may have decided that the unlock optimization couldn't be done that way, either, although I'd have to plow through a ton of -current code and, perhaps, CVS logs to see exactly what they did do - see this message [freebsd.org], for example, and this message [freebsd.org].
(And, the hypothesis in, as I remember, one of the linux-kernel messages nonwithstanding, the FreeBSD folk do have P6 machines - some of Matt's timing experiments were, as I remember, done on a Pentium III.)
The comment in the code also suggests that it might be useful to have a way of building a kernel without the lock, if it truly can be removed on all but the early PPro's to which the comment refers.
Re:FreeBSD vs. Linux stability. (Score:2)
That part showed up after that issue of KT came out; I don't know whether it showed up after I checked it earlier today or not (I'd assumed that issues of KT are invariant after publication, and I saw that issue before the note was added).
Some stuff in the FreeBSD archive indicates that they may have decided that the unlock optimization couldn't be done that way, either, although I'd have to plow through a ton of -current code and, perhaps, CVS logs to see exactly what they did do - see this message [freebsd.org], for example, and this message [freebsd.org].
(And, the hypothesis in, as I remember, one of the linux-kernel messages nonwithstanding, the FreeBSD folk do have P6 machines - some of Matt's timing experiments were, as I remember, done on a Pentium III.)
The comment in the code also suggests that it might be useful to have a way of building a kernel without the lock, if it truly can be removed on all but the early PPro's to which the comment refers.