Messages in this thread | | | Date | Mon, 11 Jan 1999 14:20:08 -0600 (CST) | From | Adam Heath <> | Subject | Re: testing/pre-7 and do_poll() |
| |
On Sun, 10 Jan 1999, Chip Salzenberg wrote:
> According to Linus Torvalds: > > There's a "pre-7.gz" on ftp.kernel.org in testing, anybody interested? > > Got it, like it -- *except* the fix for overflow in do_poll() is a > little bit off. Quoting testing/pre-7: > > if (timeout) { > /* Carefula about overflow in the intermediate values */ > if ((unsigned long) timeout < MAX_SCHEDULE_TIMEOUT / HZ) > timeout = (timeout*HZ+999)/1000+1; > else /* Negative or overflow */ > timeout = MAX_SCHEDULE_TIMEOUT; > } > > 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.
A/(B/C) = A * (C / B) = A / B * C (done this way to eliminate overflow)
MAX_SCHEDULE_TIMEOUT / 1000 * HZ
Adam
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
| |