Linux-kernel mailing list archive 1999-34,: Re: Linux Trace Toolkit

# Re: Linux Trace Toolkit

B. James Phillippe (bryan@terran.org)
Mon, 23 Aug 1999 09:27:44 -0700 (PDT)

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On Mon, 23 Aug 1999, Karim Yaghmour wrote:

> > - I like the idea of tracing bottom half handlers; now it should also
> > trace interrupts
>
> I must disagree to some extent here. I thought a lot before deciding not
> to trace interrupts. The reason is that interrupts under linux often are
> short and only take care of some hardware issues before setting a bottom
> half and "exiting". Therefore, the "important" stuff only happens in the
> bottom half.

Not necessarily.

> Moreover, when logging a certain event, the kernel trace module uses spin
> locks ... I am not sure that it is safe to use spin locks inside
> interrupts. No?

Spinlocks are the _only_ kind of lock that is safe to use in an interrupt
handler. Provided (as with any place you use them) that you are only
spinning for a very small amount of time.

cheers,
-bp

    --
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    # http://www.terran.org/~bryan

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