On Thu, Feb 23, 2006 at 10:54:02AM +0000, Josh Boyer wrote: > On Wed, 2006-02-22 at 22:19 -0600, Kumar Gala wrote: > > On Tue, 14 Feb 2006, Dale Farnsworth wrote: > > > > > From: Dale Farnsworth <dale at farnsworth.org> > > > > > > On PPC Book E processsors, we currently handle debug > > > exceptions on the critical exception stack (debug stack > > > for E200). This causes problems with the kgdb single > > > step handler, which calls smp_processor_id() and spin_lock(), > > > which reference current_thread_info(), which only works when > > > we are on the kernel stack. > > > > > > We address this by switching to the kernel stack early while > > > handling debug exceptions. Note that the entry values of r10 > > > and r11 are still saved on the critical exception (or debug) stack. > > > > > > Signed-off-by: Dale Farnsworth <dale at farnsworth.org> > > > > Paul, > > > > We were wondering if you or David remember why a specific critical > > exception stack was added in the 40x port from 2.4 to 2.6? > > I think Matt did that. And if I remember correctly, it was to avoid > corruption if you were in the middle of handling a normal interrupt and > a critical interrupt came in.
Thanks Josh, Matt was one of the "we" who were wondering. If indeed you are remembering correctly, then I think we're safe to use the normal kernel stack rather than the critical exception stack. -Dale
