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Re: L4 interrupt association


From: Espen Skoglund
Subject: Re: L4 interrupt association
Date: Wed, 14 May 2003 20:07:09 +0200

[Peter De Schrijver]
>> I do not think it makes sense to use the RTC timer in the first
>> place, since L4/X2 provides you an accurate time base using the
>> SystemClock syscall which also respects processor frequency changes
>> etc and is extremely cheap.  This also makes the code portable over
>> different hardware platforms.

> Oh, does the SystemClock give me the wall clock time then ? I was
> under the impression SystemClock gives me the time passed since
> system boot.

SystemClock gives you the number of microseconds passed since some
base time (the base time is not defined).  Calling something a wall
clock time doesn't make sense unless you also specify what time 0 of
the wall clock is.

If you want to specify a timeout 10 seconds into the future, you can
use something like:

   L4_Time_t timeout = L4_TimePoint (L4_SystemClock () + 10*1000*1000);

The timeout value can then be used for various IPC operations.  In
particular, you could say:

   L4_Sleep (timeout);

This gives you an efficient and portable way to wait for a specific
time to be reached.  You could also let N threads use the same
timeout, causing all threads to be woken up at exactly the same time.

        eSk




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