[syslinux] extlinux: missing text on serial output

[Ferenc Wagner]

"H. Peter Anvin" <hpa at zytor.com> writes:

> Ferenc Wagner wrote:

>> "H. Peter Anvin" <hpa at zytor.com> writes:
>>
>>> "say" not outputting on the serial console is weird and serious.

Hi Peter,

It occured to me that (under git syslinux-3.70-pre16-1-g43c735d)

--- a/core/parseconfig.inc
+++ b/core/parseconfig.inc
@@ -328,7 +328,7 @@ pc_label:   call commit_vk                  ; Commit any curre
nt vkernel
 ; "say" command
 ;
 pc_say:                call pc_getline                 ; "say" command
-               call writestr
+               call cwritestr
                jmp crlf                        ; tailcall
 
 ;

fixes this issue on syslinux and extlinux.  Pxelinux doesn't exhibit
this issue, it prints the say message either way.  I couldn't test
isolinux.  Also I can't tell if it's the correct fix, because I got
lost between the dozens of output functions, but this will probably be
obvious for you.

>> after dismissing the boot: prompt there is a long delay (order of a
>> minute) before output starts appearing.
>
> Hm, almost sounds like it's waiting for CTS.

I've found something which may be related.  It's not connected to
serial at all.  Here's my full config:

say hello

There's no file named linux on the floppy image, so both syslinux and
extlinux complain: "Could not find kernel image: linux".  However,
syslinux does this instantly, while extlinux "waits" for a couple of
seconds (running under QEMU) before printing this message.  If I
enable DEBUG_TRACERS (a wonderful debugging aid, thanks for putting it
into place!) extlinux floods my terminal with 288 kB of 'H's before
outputting the message.  Those seem to come from cache.inc.  I doubt
this would be normal.  What do you think?
-- 
Thanks,
Feri.