- From: Frank Mori Hess <fmhess_at_users.sourceforge.net>
- Date: Fri, 16 May 2003 14:24:13 -0500
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Friday 16 May 2003 06:25 am, 小笠原 卓 wrote: > I understand that neither the RTLinux or the RTAI allows more than one > realtime handler to be installed on a same irq (handler's address is > overwritten). But is it also a bad idea to share an irq by a realtime > and NON-realtime handlers (I have PCI-DAS1602/16, 3Com's NIC and a USB > interface on IRQ=9. I only want the handler for DAS1602 to be realtime)? > If yes, could you please explain why? Because it's impossible? When a shared interrupt line is asserted, the computer has no way of knowing which one of the devices asserted the interrupt, except by running the interrupt handlers for all the devices until one causes the interrupt to clear. The best scheme that could be accomplished would be to set the interrupt RT, then drop out of RT every time one of the non-RT devices produced an interrupt. Since an RT interrupt that drops out of RT priority unpredictably is not really an RT interrupt, it would be fairly useless. It is only possible to share an interrupt if all the devices sharing the interrupt have RT-safe interrupt handlers. - -- Frank -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (GNU/Linux) Comment: For info see http://www.gnupg.org iD8DBQE+xTre5vihyNWuA4URAjn/AJ0XqFfIEhNBRZzB5jLi1miC0tzEpwCdHwcH UavknZalJXb5fM3f0AYPLYY= =aBEL -----END PGP SIGNATURE-----
Received on 2003-05-16Z18:24:13