From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pat LaVarre <p.lavarre@ieee.org>
Subject: Re: zeroes read back more often than appended
Date: 27 Oct 2003 14:55:43 -0700
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> > List:     linux-fsdevel
> > Subject:  given fs dies if SMP, if PREEMPT, if open two or more
> >
> > ... Can anyone here advise me specifically
> > what to try next? ... trouble ... says to me
> > something in udf.ko doesn't know how to
> > reenter itself, right?

Sure.

> > So my next step is to try reading while
> > writing, to see if that breaks also, right?

I did try, but I got the wrong answer.

Writing while reading does Not break so easily.

For example, writing via a loop of (read file 0, write file 1, read file
2) works ok, at least at my desk for width x height of 0xFF600 x 0xC8
tried three times in a row.  Also I tried a read by dd in parallel with
a loop to append, again no joy.

So far, all that breaks is writing while writing.  That does break in
-test9, no matter SMP/PREEMPT, as described by this thread.

> > in -test9 as described

Either `make oldconfig` somewhere near -test9 injects some noise, or I
erred in past configurations myself.

Specifically, to have my -test9 .config differ minimally from `make
defconfig`, I had to work to ensure I agreed with defconfig on two
points:

$ egrep 'SOFTWARE|SPINLOCK' .config
# CONFIG_SOFTWARE_SUSPEND is not set
CONFIG_DEBUG_SPINLOCK_SLEEP=y
$

Pat LaVarre