[PATCH] ppc64: iSeries early printk breakage

[PATCH] ppc64: iSeries early printk breakage

[Stephen Rothwell]

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The earlier commit 8d9273918635f0301368c01b56c03a6f339e8d51
(Consolidate early console and PPCDBG code) broke iSeries because
it caused unregister_console(&udbg_console) to be called
unconditionally.  iSeries never registers the udbg_console.

This just reverts part of the change.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---

 arch/ppc64/kernel/udbg.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au
http://www.canb.auug.org.au/~sfr/

234f5032f6ccb4d72e4b74d33af55716b67d8a27
diff --git a/arch/ppc64/kernel/udbg.c b/arch/ppc64/kernel/udbg.c
--- a/arch/ppc64/kernel/udbg.c
+++ b/arch/ppc64/kernel/udbg.c
@@ -158,14 +158,20 @@ static struct console udbg_console = {
 	.index	= -1,
 };
 
+static int early_console_initialized;
+
 void __init disable_early_printk(void)
 {
+	if (!early_console_initialized)
+		return;
 	unregister_console(&udbg_console);
+	early_console_initialized = 0;
 }
 
 /* called by setup_system */
 void register_early_udbg_console(void)
 {
+	early_console_initialized = 1;
 	register_console(&udbg_console);
 }
 

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Re: [PATCH] ppc64: iSeries early printk breakage

[Milton Miller]

Does anything actually break without this patch?

My reading of unregister_console says we will acquire
the console semaphore, walk the list, fail to find the
console, relase the semaphore, and return.


Hmm... unless there is a problem with the console preference
code?  I don't see anything that should deref a bad pointer,
maybe it breaks the preference?

 From get web:

	if (console_drivers == NULL)
		preferred_console = selected_console;
	else if (console->flags & CON_CONSDEV)
		console_drivers->flags |= CON_CONSDEV;

On Sep 7, 2005, at 4:52 AM, Stephen Rothwell wrote:

> The earlier commit 8d9273918635f0301368c01b56c03a6f339e8d51
> (Consolidate early console and PPCDBG code) broke iSeries because
> it caused unregister_console(&udbg_console) to be called
> unconditionally.  iSeries never registers the udbg_console.
>
> This just reverts part of the change.
>
> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
> ---
>
>  arch/ppc64/kernel/udbg.c |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
>
> -- 
> Cheers,
> Stephen Rothwell                    sfr@canb.auug.org.au
> http://www.canb.auug.org.au/~sfr/
>
> 234f5032f6ccb4d72e4b74d33af55716b67d8a27
> diff --git a/arch/ppc64/kernel/udbg.c b/arch/ppc64/kernel/udbg.c
> --- a/arch/ppc64/kernel/udbg.c
> +++ b/arch/ppc64/kernel/udbg.c
> @@ -158,14 +158,20 @@ static struct console udbg_console = {
>  	.index	= -1,
>  };
>
> +static int early_console_initialized;
> +
>  void __init disable_early_printk(void)
>  {
> +	if (!early_console_initialized)
> +		return;
>  	unregister_console(&udbg_console);
> +	early_console_initialized = 0;
>  }
>
>  /* called by setup_system */
>  void register_early_udbg_console(void)
>  {
> +	early_console_initialized = 1;
>  	register_console(&udbg_console);
>  }
>

Re: [PATCH] ppc64: iSeries early printk breakage

[Stephen Rothwell]

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On Wed, 7 Sep 2005 06:04:36 -0500 Milton Miller <miltonm@bga.com> wrote:
>
> Does anything actually break without this patch?

Yes, an iSeries box will not boot.

> My reading of unregister_console says we will acquire
> the console semaphore, walk the list, fail to find the
> console, relase the semaphore, and return.

Consider the case that console_drivers == NULL (because we have never called register_console).
unregister_console dereferences console_drivers ...

-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au
http://www.canb.auug.org.au/~sfr/

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