It has just come to my attention that drivers/video/vgacon.c does an
unconditional cli() and sti() instead of save_flags/restore_flags.
This has the unfortunate side effect of possibly enabling interrupts
when you do console I/O, which kdb does. AFAICT this should only be a
problem if the screen is blanked when you enter kdb, vga_vesa_unblank
is the only mainline code that does sti(), the rest are in font
This bad code might explain why people have seen interrupt routines
being reentered under kdb. There is a patch by James Simmons
<jsimmons@xxxxxxxx> on l-k to fix vgacon.