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    SubjectRe: [PATCH *] use 64 bit jiffies
    On 4 February 2003 10:27, Robert de Bath wrote:
    > On Tue, 4 Feb 2003, Denis Vlasenko wrote:
    > > Jiffy Wrap Bugs
    > >
    > > There were reports of machines hanging on jiffy wrap.
    > > This is typically a result of incorrect jiffy use in some driver.
    > > Ask Tim - he is hunting those problems regularly, but he is
    > > outnumbered by buggy driver authors. :(
    > >
    > > There is a better solution to ensure correct jiffy wrap handling in
    > > *ALL* kernel code: make jiffy wrap in first five minutes of uptime.
    > > Tim has a patch for such config option. This is almost right.
    > > This MUST NOT be a config option, it MUST be mandatory in every
    > > kernel. Driver writers would be bitten by their own bugs and will
    > > fix it themself. Tim, what do you think?
    > How about an option, either the jiffy timer wraps at 5 minutes or
    > process 1 gets sent a SIGINT after 24 hours ? That way a driver
    > with an MIA author can still be used even if it's buggy, just not
    > for very long.

    I prefer buggy driver be fixed ASAP. The first step is to know
    that there *is* a (jiffywize-) buggy driver or something.

    Jiffie wrap at 5 mins is done this way: jiffies is initialized to -5*60*HZ
    instead of zero at boot. Accounting code is adjusted e.g. not to show 400+
    days uptime (it subtracts -5*60*HZ from jiffies).

    Jiffies wraps to zero in five minutes. Box should survive with no probs.
    If it instead hangs, oops or otherwise feeling bad, you have a jiffy wrap
    bug somewhere.

    Today you need to wait 400 or so days before you can test what will happen.
    Production servers' admins getting a bit nervous close to that date ;)

    A nice printk "Timer code check..." at jiffies = -30*HZ
    and "...timer code check passed" at jiffies = 30*HZ will let us have
    good bug reports ("what was your last log message?") and would not
    scare people. "A jiffie would wrap in 5 seconds!" is not that good -
    please do not unnecessarily scare new users ;)
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