BeOS Driver Tips and Tricks

Subject: Re: dev #3033: aliens generating interrupts? Date: Wed, 2 Apr 1997 17:02:59 -0800 From: William Adams To: thorns@cs.mcgill.ca >Subject: Re: dev #3033: aliens generating interrupts? >To: William Adams >Date: Wed, 2 Apr 1997 12:29:34 -0800 (PST) > >This message is generated when the processor get interrupted, but when >it goes to look at the interrupt source register, none of the >interrupt sources appear to be interrupting. > >This typically happens because of a device driver bug. Once common problem >is that the device driver's interrupt handler is calling >release_sem instead of release_sem_etc with the DO_NOT_RESCHEDULE >flag set, and then doing something to clear the interrupt on the >actual device hardware. Since calling release_sem does in fact cause >a reschedule, the interrupt handler will continue running 'later', possibly >even on another processor (on beboxes and MP macs). If the device in the >meantime has another interrupt ready, and the interrupt handler then clears >the interrupt, you lose an interrupt! > >If the clearing happens at just the right time, i.e after the device has >generated the interrupt causing the cpu taking i.o interrupts to be >interrupted, but before that cpu can read the interrupt source register, >you get the wonderful 'ALIENS...' message. > >> >>Anyone want to comment on this. >>-- William >> >>>Date: Tue, 1 Apr 1997 20:53:32 -0500 (EST) >>>To: devsupport@be.com >>>Subject: dev #3033: aliens generating interrupts? >>>From: Simon Thornington >>> >>>I just got a message on serial4 as follows: >>> >>>ALIENS ARE GENERATING INTERRUPTS! CALL BOB 80005ec4 40220020 >>> >>>I wouldn't think anything of it, except that I am writing a device >>>driver and have been having problems with interrupts that don't appear >>>to be from me. What does this message mean? >>> >>>Cheers, >>> >>>Simon. >>>

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