Re: Hotplug bug in Linux 2.4.21?

[Adrien Beau <adrien.beau@free.fr>]

On Saturday 21 June 2003 18:11, Adrien Beau wrote:
> 
> > You'll need to find some other way of knowing when a lockfile
> > exists and is stale... something that can handle more than
> > one process that is started at identical times (or nearly
> > so).
>
> Even with the very short interval between them, the scripts
> find without error that the lockfile exists, and read it
> without error. However, they then go to decide that 1 is
> greater than 60, and *that*, I can't understand.
>
> I'm going to put some sleep(1) at appropriate places and see if
> this helps.

It quickly turned out that this was a wrong idea, since the scripts
are started at the same time. It only makes things worse, since the
the lockfile then disappears while a script is sleeping.

It doesn't matter any more, though, since I have found a solution to
this problem. I tried to find what made the test fail. It turns out
that

  expr $currenttime '-' $timestamp '<' $MAX_LOCK_AGE

returns 1 to stdout, which means that indeed, expr thinks that 0 or 1
are less than 60. The bug is that, when run in "normal" conditions,
at a few seconds interval, the above command has an exit status of 0,
but when run in "stress" conditions, at a few hundredth of seconds
interval, its exit status is 1. That's just weird (a bug in the kernel
or glibc, or what?), but that can be worked around. I ended up using

  [ `expr $currenttime '-' $timestamp` -lt $MAX_LOCK_AGE ]

instead, which works fine.

-- 
adrien.beau@free.fr - http://adrien.beau.free.fr/



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