Messages in this thread | | | Date | Fri, 23 Sep 2005 21:44:10 -0700 | From | Nish Aravamudan <> | Subject | Re: [patch] sys_epoll_wait() timeout saga ... |
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On 9/23/05, Willy Tarreau <willy@w.ods.org> wrote: > Hi Davide, > > On Fri, Sep 23, 2005 at 11:13:30AM -0700, Davide Libenzi wrote: > > > > The sys_epoll_wait() function was not handling correctly negative > > timeouts (besides -1), and like sys_poll(), was comparing millisec to > > secs in testing the upper timeout limit. > > > > > > Signed-off-by: Davide Libenzi <davidel@xmailserver.org> > > > > > > - Davide > > > --- a/fs/eventpoll.c 2005-09-23 10:56:57.000000000 -0700 > > +++ b/fs/eventpoll.c 2005-09-23 11:00:06.000000000 -0700 > > @@ -1507,7 +1507,7 @@ > > * and the overflow condition. The passed timeout is in milliseconds, > > * that why (t * HZ) / 1000. > > */ > > - jtimeout = timeout == -1 || timeout > (MAX_SCHEDULE_TIMEOUT - 1000) / HZ ? > > + jtimeout = timeout < 0 || (timeout / 1000) >= (MAX_SCHEDULE_TIMEOUT / HZ) ? > > MAX_SCHEDULE_TIMEOUT: (timeout * HZ + 999) / 1000; > > Here, I'm not certain that gcc will optimize the divide. It would be better > anyway to write this which is equivalent, and a pure integer comparison : > > + jtimeout = timeout < 0 || timeout >= 1000 * MAX_SCHEDULE_TIMEOUT / HZ ? > > MAX_SCHEDULE_TIMEOUT: (timeout * HZ + 999) / 1000;
Just a question here, maybe it's dumb.
* and / have the same priority in the order of operations, yes? If so, won't the the 1000 * MAX_SCHEDULE_TIMEOUT overflow (MAX_SCHEDULE_TIMEOUT is LONG_MAX)? I really think this code just move to the same thing that sys_poll() does to avoid overlflow (I fixed the bug Alexey was experiencing, so I think the changes are safe now). In any case, this code is approaching unreadable with lots of jiffies <--> human-time units manipulations done in non-standard ways, which the updated sys_poll() also tries to avoid.
Thanks, Nish - 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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