Re: [Bug #14015] pty regressed again, breaking expect and gcc's testsuite

Mikael Pettersson
2009-09-01T01:34:14Z

Mikael Pettersson writes:
> Rafael J. Wysocki writes:
> > On Saturday 29 August 2009, Mikael Pettersson wrote:
> > > Mikael Pettersson writes:
> > > > Rafael J. Wysocki writes:
> > > > > On Thursday 27 August 2009, Mikael Pettersson wrote:
> > > > > > On Tue, 25 Aug 2009 22:34:53 +0200 (CEST), Rafael J. Wysocki wrote:
> > > > > > > The following bug entry is on the current list of known regressions
> > > > > > > from 2.6.30. Please verify if it still should be listed and let me know
> > > > > > > (either way).
> > > > > > >
> > > > > > >
> > > > > > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=3D14015
> > > > > > > Subject : pty regressed again, breaking expect and gcc's testsuite
> > > > > > > Submitter : Mikael Pettersson <mikpe-1zs4UD6AkMk@public.gmane.org>
> > > > > > > Date : 2009-08-14 23:41 (12 days old)
> > > > > > > References : http://marc.info/?l=3Dlinux-kernel&m=3D125029329805643&w=3D4
> > > > > >
> > > > > > Not fixed. With 2.6.31-rc7 I'm still seeing repeatable testsuite
> > > > > > failures on powerpc64. Reverting to 2.6.30 makes the failures go away.
> > > > >
> > > > > Thanks for the update.
> > > > >
> > > > > I guess 2.6.31-rc8 doesn't make any difference, does it?
> > > >
> > > > I've scheduled a number of gcc bootstraps and testsuite runs
> > > > with -rc8 on x86, powerpc64, and arm. I'll post an update in
> > > > a day or so.
> > >
> > > 2.6.31-rc8 results in bogus testsuite failures on all three platforms.
> >
> > That may be a result of the known inotify borkage in -rc8 that has been fixed
> > in the current Linus' tree.
>
> No, it's the same old semi-random pty breakage. My kernels are built
> without inotify.
>
> A bisection has identified Alan's
>
> pty: Rework the pty layer to use the normal buffering logic
> d945cb9cce20ac7143c2de8d88b187f62db99bdc
>
> as the culprit. This patch introduces a massive number of bogus
> failures in the gcc testsuite. Subsequent pty/tty patches do fix
> most of those failures, but clearly not all.

Starting with 2.6.31-rc8 and reverting

85dfd81dc57e8183a277ddd7a56aa65c96f3f487 pty: fix data loss when stopped (^S/^Q)
d945cb9cce20ac7143c2de8d88b187f62db99bdc pty: Rework the pty layer to use the normal buffering logic

in that order gives me a kernel that works on both x86 and powerpc64.

So the bug is definitely limited to the pty buffering logic change.