[PATCH] gettimeofday stability

Gabriel Paubert paubert at iram.es
Fri Apr 13 04:09:16 EST 2001

On Wed, 11 Apr 2001, Karim Yaghmour wrote:

> While porting the Linux Trace Toolkit to PPC I noticed a problem
> that may be explained by the symptoms described. The way it works
> is that LTT uses do_gettimeofday() to stamp the events that occur.
> Occasionnaly, a trace would contain entries where the timestamp
> will jump (from one event to the next) of approximately 4295 seconds.
> Later on, this would come back to a "normal" value. And the
> 4295 seconds are 2^32/1000000. Hence the underflow.
> This has been noticed with both 2.2.x and 2.4.x kernels.

Given that time handling is completely different in 2.2 and 2.4, it is
surprising. This would indicate that a decrementer interrupt has happened
too early.

How often does it happen ? Does it still happen with recent kernels ?
Were you running something that touches the decrementer (MOL, RTLINUX) ?


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