From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [Xenomai-core] [BUG] x86 TSC emulation broken From: Philippe Gerum In-Reply-To: <44C3B1DB.2040807@domain.hid> References: <44C3B1DB.2040807@domain.hid> Content-Type: text/plain Date: Sun, 23 Jul 2006 22:28:27 +0200 Message-Id: <1153686507.8053.9.camel@domain.hid> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Reply-To: rpm@xenomai.org List-Id: "Xenomai life and development \(bug reports, patches, discussions\)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: xenomai-core On Sun, 2006-07-23 at 19:28 +0200, Jan Kiszka wrote: > 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 gen* > erating code). There is an issue in the Adeos 2.4 patch (1.2-05) which is not preventing the kernel from poking into the 8254 registers to determine the current time offset. > > 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. Mm, through the host timer service, it should at least each 10ms period. > > 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 > > _______________________________________________ > Xenomai-core mailing list > Xenomai-core@domain.hid > https://mail.gna.org/listinfo/xenomai-core -- Philippe.