On Sat, 31 Jul 2021, Christophe Leroy wrote:

> > 
> > Stan Johnson contacted me about a regression in mainline that he 
> > observed on his G3 Powerbooks. Using 'git bisect' we determined that 
> > this patch was the cause of the regression, i.e. commit 4c0104a83fc3 
> > ("powerpc/32: Dismantle EXC_XFER_STD/LITE/TEMPLATE").
> > 
> > When testing 4c0104a83fc and all subsequent builds, various user 
> > processes were liable to segfault. Here is the console log that Stan 
> > provided:
> 
> Hi, i will be able to look at that more in details next week, however I 
> have a few preliminary qurstions.
> 
> Can you reliabily reproduce the problem with the said commit, and can 
> you reliabily run without problem with the parent commit ? 

Yes and yes. (I already asked Stan to establish those things before I 
contacted the list.)

> I'm asking because at first look that commit doesn't bring any 
> functionnal change.
> 
> Coukd you provide your .config ?
> 

Please see attached. My understanding is that all of Stan's builds were 
performed like this:

$ cp ../dot-config-powermac-5.13 .config
$ make ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu- -j4 clean olddefconfig vmlinux

> Could you try without CONFIG_VMAP_STACK
> 

Stan, would you please test the following build:

$ git checkout v5.13
$ cp ../dot-config-powermac-5.13 .config
$ scripts/config -d CONFIG_VMAP_STACK
$ make ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu- -j4 clean olddefconfig vmlinux