jiffies wraparound

MOLNAR Ingo (mingo@chiara.csoma.elte.hu)
Sun, 18 Oct 1998 09:03:43 +0200 (CEST)


On Sun, 18 Oct 1998, Alan Cox wrote:

> > It's a beauty wart, it's been there forever, and we know that machines
> > actually tend to survive it fine. So far I have _one_ person who has
>
> 1.2 survives mostly, 2.0 survives mostly, 2.1.x doesnt survive

well i have tried to simulate a jiffies wraparound with pre2-126, and it
has survived more or less. There are a few strange things that happen near
and after the wraparound:

- the IDE driver got confused somewhat:

8:49am up 496 days, 23:47, 5 users, load average: 0.57, 0.43, 0.22

hda: timeout waiting for DMA
hda: irq timeout: status=0xd0 { Busy }
hda: DMA disabled
changing jiffies from fffefd63 to ffff0d63.
ide0: reset timed-out, status=0xd0
hda: status timeout: status=0xd0 { Busy }
hda: drive not ready for command
ide0: reset: success

- when the wraparound happens, all network connections and all terminal
lines are killed at once.

- gpm goes crazy, mouse is very jumpy, but this can be fixed by restarting
gpm.

otherwise things look mostly fine, no network connection is stuck, no
process is hanging, no kernel oops. The time.c change in 2.1.126 has
indeed made time handling more robust, while 2.1.125 oopses with division
by zero, the 2.1.126 time code survived this quick 'time travel' without
problems. Apart from processes getting killed during wraparound, there is
no big problem, is there?

-- mingo

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