Messages in this thread | | | Date | Mon, 11 Jan 1999 01:26:21 -0500 | From | Chip Salzenberg <> | Subject | Re: testing/pre-7 and do_poll() |
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According to Linus Torvalds: > On Sun, 10 Jan 1999, Chip Salzenberg wrote: > > However, the maximum legal millisecond timeout isn't (as shown) > > MAX_SCHEDULE_TIMEOUT/HZ, but rather MAX_SCHEDULE_TIMEOUT/(1000/HZ). > > So this code will turn some large timeouts into MAX_SCHEDULE_TIMEOUT > > unnecessarily. > > Note the comment (and do NOT look at the speeling). In particular, > we need to make sure the _intermediate_ value doesn' toverflow.
Of course; that's obvious. What's perhaps less obvious is that I'm suggesting a change in the calculation of timeout -- a change which avoids the creation of unnecessarily large _intermediate_ values.
> > ! if (timeout < 0) > > ! timeout = MAX_SCHEDULE_TIMEOUT; > > ! else if (timeout) > > ! timeout = ROUND_UP(timeout, 1000/HZ); > > Eh? And re-introduce the original bug?
Well, I forgot the (unsigned long) cast, as someone else noted:
timeout = ROUND_UP((unsigned long) timeout, 1000/HZ);
Otherwise, the code is Just Right. -- Chip Salzenberg - a.k.a. - <chip@perlsupport.com> "When do you work?" "Whenever I'm not busy."
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