Chris Lalancette
2009-Sep-16 06:25 UTC
[Xen-devel] [PATCH]: Remove "buffer half full" check from guest_console_write
All, We''ve seen a case where booting Xen on a certain platform configured with a serial console takes an unreasonably long time to boot (on the order of hours). Now, on this particular piece of hardware, it was determined that the serial firmware actually has a bug. That being said, I''m not sure that preventing boot in the face of buggy serial hardware is a reasonable course of action. Bare-metal Linux, for instance, boots fine although characters might be dropped along the way. The problem seems to be the check in guest_console_write(), which has a quench-type check at the top of the loop. I assume the check is to prevent the guest from completely flooding the serial console, but: 1) It seems like a layering violation; a check here can (and does) prevent the lower level serial code from doing the right thing. 2) It seems redundant since c/s 17851. That c/s added a very similar check into __serial_putc(), so I don''t think we need it here anymore. This patch just removes the check entirely. With this patch and c/s 17851 in place, the problematic hardware boots in a normal amount of time (although it still might drop characters, but I think this is the best we can do). Signed-off-by: Chris Lalancette <clalance@redhat.com> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel