Subject: Re: [linux-audio-dev] MCS: 64 bit timestamps?
From: Paul Barton-Davis (pbd_AT_Op.Net)
Date: la loka 16 1999 - 22:57:22 EDT
Florian writes:
>> current_cycle_counter = read_tsc ();
>> cycle_diff = current_cycle_counter -
>> cycle_counter_at_start_of_control_loop;
>
>Forgive me the dumb question, but how is this supposed to work on an
>SMP box?
which part bothers you, "read_tsc" or the subtraction of non-atomic 64
bit quantities ?
if the cycle counters are not (1) synchronized at bootup and (2) not
running at the same rate, then as David pointed out, its hardly
*symmetric* multiprocessing is it ?
the non-atomic 64 bit stuff is more of a problem. i don't have an easy
answer yet (or rather, i don't have an answer that doesn't involve
taking a mutex).
--p
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