From owner-freebsd-hackers  Thu Jan 11  7:55:34 2001
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Message-ID: <3A5DCFE0.D52CD8E6@elischer.org>
Date: Thu, 11 Jan 2001 07:23:12 -0800
From: Julian Elischer <julian@elischer.org>
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To: Mohana Krishna Penumetcha <pmk@sasi.com>
Cc: Alfred Perlstein <bright@wintelcom.net>,
	freebsd-hackers@FreeBSD.ORG
Subject: Re: kernel debugging!!!
References: <Pine.LNX.4.10.10101111709560.1340-100000@pcs113.sasi.com>
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Mohana Krishna Penumetcha wrote:
> 
> > * Mohana Krishna Penumetcha <pmk@sasi.com> [010111 03:08] wrote:
> > >
> > >
> > > > Afaik, on i386 you have ~4k of kernel stack, however you have to
> > > > realize that driver entry can come from an interrupt generated when
> > > > the stack is already nearly exhausted.  I'm not really that much
> > > > of a driver programmer, but I've heard of people facing this problem
> > > > before, solutions varied, but since each driver instance is single
> > > > threaded you can pre-allocate via malloc (i think) the space you
> > > > need and attach it to the per-driver data structure (softc afaik).
> > >
> > >     i am confused between the kernel stack in kernel space (where ISRs
> > > are called) and kernel stack each process has. the UPAGES constant
> > > defines the size of process kernel stack. does it define kernel stack in
> > > kernel space also?? (fig 3.1, page 51, BSD book)
> > >
> > >     BTW, memory for softc is allocated from the heap in newbus
> > > architecture.
> >
> > I'm pretty sure interrupts are piggybacked on the user-kernel-stack.
> >
> 
>         this is o.k. when the system is up and running. but what about
> boot-up time when there is no process, is there any stack meant for
> this?


There is always a stack  for you..(there is an idle stack for just this case).

The example driver in -current (not the one in 4.x) 
might be if interest to you.
http://www.freebsd.org/cgi/cvsweb.cgi/src/share/examples/drivers/make_device_driver.sh

(beware that that may have been wrapped by my mailer on tranmit.)

> 
> > How about trying the simple printf idea and letting us know if
> that > works?
> 
>         panic is coming in the middle of the routine. i am printing many
> messages before the panic.
> 
> --
> mohan
> 
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-- 
      __--_|\  Julian Elischer
     /       \ julian@elischer.org
    (   OZ    ) World tour 2000
---> X_.---._/  from Perth, presently in:  Budapest
            v



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