Date: Thu, 30 Mar 2000 13:09:10 -0800 From: Eric Peterson <ericp@troikanetworks.com> To: 'Samuel Tardieu' <sam@inf.enst.fr> Cc: "'hackers@freebsd.org'" <hackers@freebsd.org>, 'Mike Smith' <msmith@freebsd.org> Subject: RE: Deferred procedure call available? Message-ID: <C7CA595F9B9FD311A40D009027DC4A856E7E3E@host03.troikanetworks.com>
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> -----Original Message----- Samuel Tardieu [mailto:sam@inf.enst.fr] writes: > Sent: Thursday, March 30, 2000 11:46 AM > To: Eric Peterson > Cc: 'hackers@freebsd.org' > Subject: Re: Deferred procedure call available? > > > >>>>> "Eric" == Eric Peterson <ericp@troikanetworks.com> writes: > > Eric> Sometimes called "task queues" or "deferred callbacks", they > Eric> allow an interrupt handler to schedule a (possibly predefined) > Eric> function to be called outside the context of the interrupt. > > (not an answer, just a suggestion) Is there anything you cannot do > with a userland program, that will be resumed by the interrupt > handler? Doing this even gives you the possibility of choosing the > priority of the deferred handler relative to other handler and regular > processes (as eCos does). Sam, Thanks for the response. With regard to your suggestion (my ignorance of FreeBSD drivers certainly shows through here, but...): 1. I'm porting an existing driver, so am trying to keep its basic structure intact. I don't believe that a user-mode entity has access to the memory/device address space I need to get to. 2. I suspect that going from kernel to (even high priority) user mode entails a non-trivial performance penalty (somebody please correct me if not!) One other approach I was thinking about was to have a sleeping kernel thread that I could wakeup when I needed to schedule a function to be called. I'm going to try out the timeout(9) routine that Mike Smith suggested, looks like just the ticket (thanks again, Mike). Regards, Eric -- Eric Peterson WB6PYK ericp@troikanetworks.com PGP: http://pgp5.ai.mit.edu:11371/pks/lookup?op=get&search=0x4DA8EEF1 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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