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From: John Dyson <dyson>
Message-Id: <199508081304.GAA27709@freefall.cdrom.com>
Subject: Re: cvs commit: src/sys/i386/isa syscons.cy
To: bde@zeta.org.au (Bruce Evans)
Date: Tue, 8 Aug 1995 06:04:37 -0700 (PDT)
Cc: bde@zeta.org.au, jkh@time.cdrom.com, CVS-commiters@freefall.cdrom.com,
        cvs-sys@freefall.cdrom.com
In-Reply-To: <199508081248.WAA08529@godzilla.zeta.org.au> from "Bruce Evans" at Aug 8, 95 10:48:57 pm
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> 
> >> Actually it isn't really OK to simply substitute M_NOWAIT with M_WAITOK.
> 
> >Argh.  Perhaps I was too hasty.  If John decides to rearchitect this,
> >I'll pull it out of 2.1
> 
> It has a lot of company.  I looked at all the isa drivers that use M_WAITOK
> and there seems to be a problem in them all.  Some of them bogusly check
> whether the waiting malloc() returns 0 and could probably be fixed easily
> by switching to a non-waiting malloc().  There aren't many isa drivers
> with the problem so fixing it should be manageable especially if it is
> acceptable for open() to return ENOMEM.
> 
> Bruce
> 
Actually, I believe that the drivers should generally try to handle the
low memory conditions correctly.  I don't want to have sporadic program
failures just because memory is low.  I would like to see ENOMEM to mostly
mean "out of VM".  Note that memory can be low fairly often...  For
example my syscons problem in 4MB!!!  There would probably be more
program failures (and then that would reflect on the system quality,
whether or not the calling program should handle the problem "correctly".)
Right now, the syscons changes mostly keep the system from crashing, and
a proper fix should be implemented in the next couple of days.

John
dyson@root.com