I have a hack that works. Perhaps it will give a bit more understanding so that
a proper patch can be created. My changes were applied on top of 4.9-rc1 with
the patch from
https://www.linux-mips.org/archives/linux-mips/2016-10/msg00130.html, and were
as follows:
Index: linux/kernel/printk/printk.c
===================================================================
--- linux.orig/kernel/printk/printk.c 2016-10-24 12:29:17.838938604 -0500
+++ linux/kernel/printk/printk.c 2016-10-24 19:31:20.012593000 -0500
@@ -2657,7 +2657,9 @@
* didn't select a console we take the first one
* that registers here.
*/
- if (preferred_console < 0 && !of_specified_console) {
+ pr_info("Before: newcon->device %p, newcon->setup %p\n", newcon->device,
newcon->setup);
+ if ((preferred_console < 0 && !of_specified_console) ||
+ !newcon->setup) {
if (newcon->index < 0)
newcon->index = 0;
if (newcon->setup == NULL ||
@@ -2670,6 +2672,7 @@
}
}
+ pr_info("After: newcon->device %p, newcon->setup %p\n", newcon->device,
newcon->setup);
/*
* See if this console matches one we selected on
* the command line.
The changes in commit 05fd007e4629 prevent the body of the 'if
((preferred_console < 0 ...' loop from ever being executed; however, the failure
indicates that we do need to go through this code at least once. I tested
various quantities, and !newcon->setup was the only one that helped.
The outputs from the pr_info statements above and the changes in console as
shown by 'dmesg | egrep "console|newcon" are:
[ 0.000000] Before: newcon->device (null), newcon->setup (null)
Part of the body of if executed
[ 0.000000] After: newcon->device (null), newcon->setup (null)
[ 0.000000] bootconsole [udbg0] enabled
[ 0.001581] Before: newcon->device c0326e34, newcon->setup (null)
We now have newcon->device set, Part of body of if executed
[ 0.001934] After: newcon->device c0326e34, newcon->setup (null)
[ 0.002285] console [tty0] enabled
[ 0.002595] bootconsole [udbg0] disabled
[ 0.002913] Before: newcon->device c032cc4c, newcon->setup c032cc80
This time the body of if is not executed and will not be executed
anymore.
[ 0.002925] After: newcon->device c032cc4c, newcon->setup c032cc80
[ 0.002943] Before: newcon->device c0331ad8, newcon->setup c0331c34
[ 0.002956] After: newcon->device c0331ad8, newcon->setup c0331c34
[ 0.003060] Before: newcon->device c0331ad8, newcon->setup c068dbc8
[ 0.003074] After: newcon->device c0331ad8, newcon->setup c068dbc8
[ 0.003322] Before: newcon->device c0331ad8, newcon->setup c068ddc4
[ 0.003335] After: newcon->device c0331ad8, newcon->setup c068ddc4
[ 1.993661] Before: newcon->device c0331ad8, newcon->setup c068dbc8
[ 1.993759] After: newcon->device c0331ad8, newcon->setup c068dbc8
[ 1.994395] Before: newcon->device c0331ad8, newcon->setup c068dbc8
[ 1.994492] After: newcon->device c0331ad8, newcon->setup c068dbc8
Larry
