more stack hungry as compared to the old one that my RX2660 gets
a machine check and spontaneously reboots at the time the USB DVD
drive is found and attached to CAM as a mass storage device. This
doesn't happen always, but definitely varies per kernel build.
Likewise when using a 128-byte printf buffer. The additional 128
bytes that printf needs seems to be enough to have the memory stack
and register stack collide and causing a machine check.
Thus: Bump KSTACK_PAGES from 4 to 5.
b475d22d67