Re: No 100 HZ timer!

Mark Salisbury
2001-04-16T23:52:10Z

> Given a system speed, there is a repeating timer rate which will consume
> 100% of the system in handling the timer interrupts. An attempt will
> be made to detect this rate and adjust the timer to prevent system
> lockup. This adjustment will look like timer overruns to the user
> (i.e. we will take a percent of the interrupts and record the untaken
> interrupts as overruns)

just at first blush, there are some things in general but I need to read
this again and more closely....

but, with POSIX timers, there is a nifty little restriction/protection built
into the spec regarding the re-insertion of short interval repeating timers.
that is: a repeating timer will not be re-inserted until AFTER the
associated signal handler has been handled.

this has some interesting consequences for signal handling and signal
delivery implementations, but importantly, it ensures that even a flood of
POSIX timers with very short repeat intervals will be handled cleanly.

I will get more detailed comments to you tomorrow.

Mark Salisbury