Messages in this thread |  | | Subject | Re: Regression in 4.9-rc1 for PPC32 - bisected to commit 05fd007e4629 | From | Larry Finger <> | Date | Sat, 22 Oct 2016 12:36:03 -0500 |
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On 10/20/2016 12:55 AM, Larry Finger wrote: > Kernel 4.9-rc1 fails to boot on my PowerBook G4 Aluminum (32-bit PowerPC) with > the following splat: > > Kernel Panic - not synching: Attempted to kill init: exitcode = 0x00000200 > > Call trace: > > dump_stack+0x24/0x34 (unreliable) > panic+0x110/0x2ac > do_exit+0x464/0x834 > do_group_exit+0x84/0xac > __wake_up_parent+0x0/0x34 > ret_from_syscall+0x0/0x40 > > As the panic happens very early, I was not able to capture the output, thus the > above was entered by hand. > > The problem was bisected to commit 05fd007e4629 ("console: don't prefer first > registered if DT specifies stdout-path"). Examining that patch and testing the > various hunks, I found that the system booted fine when I eliminated the hunk at > > --- a/drivers/of/base.c > +++ b/drivers/of/base.c > @@ -2077,6 +2077,8 @@ void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align)) > name = of_get_property(of_aliases, "stdout", NULL); > if (name) > of_stdout = of_find_node_opts_by_path(name, > &of_stdout_options); > + if (of_stdout) > + console_set_by_of(); > } > > if (!of_aliases) > > Similarly, it would boot if I eliminated the hunk at > > --- a/kernel/printk/printk.c > +++ b/kernel/printk/printk.c > @@ -2647,7 +2658,7 @@ void register_console(struct console *newcon) > * didn't select a console we take the first one > * that registers here. > */ > - if (preferred_console < 0) { > + if (preferred_console < 0 && !of_specified_console) { > if (newcon->index < 0) > newcon->index = 0; > if (newcon->setup == NULL || > > The problem happens when of_specified_console is true, and the code following > the modified if statement above is not executed. In my .config, CONFIG_OF=y. > > As always, I will be happy to test any fixes.
I have done some testing regarding this regression. I hope that this will help in finding a fix for the problem.
When I remove the test of "of_specified_console" in the if statement above, nothing changes in the first time through register_console(). At this point, newcon->device is NULL, and "bootconsole [udbg0] selected" is logged sometime after that call. The second time register_console() is called, newcon->device is c0323b48, and the log contains
console [tty0] enabled console [udbg0] disabled
At this point newcon->device has been changed to c0329960. Routine register_console() is called 5 more times with a netcon->device value of c032e7ec, but the console is not changed again.
If the code is never allowed to execute the if block in question, the bootconsole [udbg0] is never replaced, which leads to the kernel panic.
Larry
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