Re: file offset corruption on 32-bit machines?

[Pavel Machek]

On Tue 2008-04-15 22:28:55, Peter Zijlstra wrote:
> On Tue, 2008-04-15 at 22:06 +0200, Pavel Machek wrote:
> 
> > > > I'm not saying this kernel bug is likely to hit in practice. It is
> > > > still a kernel bug.
> > > > 
> > > > Is the slowdown of lseek worth getting rid of this minor bug? Not
> > > > sure, probably yes.
> > > 
> > > I think a slow down is the worse choice.  Adding a note to the
> > > documentation saying that "By the way, on 32bit systems the seek call is
> > > not atomic for 64bit file offsets, so if you happen to issue two at
> > 
> > That would be very wrong addition to documentation. If you really
> > wanted to do something like this, you would probably want to say
> > something like
> > 
> > "Doing concurrent seeks on one file is undefined. Kernel may end up
> > with seeking to some other place."
> > 
> > Unfortunately, you'd have to get this addition into POSIX standard...
> 
> Is not treating the point not similar to undefined? And undefined
> semantics cover pretty much anything, including the current behaviour.
> 
> FWIW I really think this issue is a non-issue; one cannot expect sane
> behaviour of unsynchronized usage of a shared resource.

Why not? Kernel syscalls are traditionally atomic, and Lennard seems
to have found sentence in POSIX that says so.
									Pavel
-- 
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