Re: Migration of kernel interfaces to seq_files breaks pread()consumers
From: Alexey Dobriyan
Date: Sun Jan 25 2009 - 07:02:58 EST
On Sat, Jan 24, 2009 at 06:19:24PM -0800, Andrew Morton wrote:
> On Fri, 16 Jan 2009 23:51:35 -0800 (PST) Paul Turner <pjt@xxxxxxxxxx> wrote:
>
> >
> > (Specifically) Several interfaces under /proc have been migrated to use
> > seq_files. This was previously observed to be a problem with VMware's
> > reading of /proc/uptime. We're now running into the same problem on
> > /proc/<pid>/stat; we have many consumers performing preads on this
> > interface which break under new kernels.
> >
> > Reverting these migrations presents other problems and doesn't scale with
> > everyones' pet dependencies over an abi that's been
> > broken :(
>
> We changed userspace-visible behaviour and broke real applications.
> This is a serious matter. So serious in fact that your report has
> languished without reply for a week.
>
> Reverting those changes until we have a suitable reimplementation which
> doesn't bust userspace is 100% justifiable.
>
> In which kernel versions is this regression present?
>
> What would a revert look like? Big and ugly or small and simple? Do
> the original commits (which were they?) still revert OK?
This is bug http://bugzilla.kernel.org/show_bug.cgi?id=11856
Some of us think what to do here.
Original patch not revertable as is.
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