From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Sun, 23 Jul 2006 19:28:59 +0200
From: Jan Kiszka <jan.kiszka@domain.hid>
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Subject: [Xenomai-core] [BUG] x86 TSC emulation broken
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Hi,

I happened to switch on some CPU type that enabled the Xenomai's TSC
emulation code. The result was an ugly lock-up: endless loop in the
timer IRQ handler.

The reason: the TSC emulation collides with the VT sound output / the PC
speaker driver. Over 2.6, one can easily avoid this my switching off
CONFIG_INPUT_PCSPKR. 2.4 requires to export and than manipulate
kb_mksound (the pointer to the sound generating code).

The latter pointer rang some bell. I once fixed a broken RTAI build due
to that code. So I pulled out vulcano and actually found the related
code + an extension of the original ipipe patch to export kb_mksound. I
guess it would have been too complicated for Paolo to explain the reason
of this export to us...

Anyway, this digging revealed another potential breakage in the
emulation code: RTAI takes care to read the emulated TSC at least once
per 50 ms, to avoid overflows I assume. Xenomai does not.

Before spending "some" time on a clean (in contrast to what I just read
in foreign code...) fix for Xenomai, I would like to cross-check if this
emulation is still considered useful. No one seems to use it, otherwise
we should have received complaints much earlier.

Fix it or drop it?

Jan


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