[PATCH] allow console drivers to be called early

[PATCH] allow console drivers to be called early

[Jesse Barnes]

[-- Attachment #1: Type: text/plain, Size: 541 bytes --]

This is a simple patch to allow arches to set early_printk_ok if they've 
registered console drivers that support early operation.  I've got an ia64 
specific bit and an sn2 specific bit that I can post for reference if 
anyone's interested, but they're pretty straightforward, so I'm just posting 
this for comments.  The ia64 one just adds a register_early_consoles() 
function to the ia64 code that gets called early on in setup_arch.  All it 
does is call the init routines of console drivers that are setup to do early 
printks.

Jesse

[-- Attachment #2: early-printk.patch --]
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===== kernel/printk.c 1.37 vs edited =====
--- 1.37/kernel/printk.c	Tue May  4 10:48:06 2004
+++ edited/kernel/printk.c	Fri May  7 15:01:33 2004
@@ -54,6 +54,7 @@
 EXPORT_SYMBOL(console_printk);
 
 int oops_in_progress;
+int early_printk_ok;
 
 /*
  * console_sem protects the console_drivers list, and also
@@ -526,7 +527,7 @@
 			log_level_unknown = 1;
 	}
 
-	if (!cpu_online(smp_processor_id()) &&
+	if (!early_printk_ok && !cpu_online(smp_processor_id()) &&
 	    system_state != SYSTEM_RUNNING) {
 		/*
 		 * Some console drivers may assume that per-cpu resources have
===== include/linux/kernel.h 1.48 vs edited =====
--- 1.48/include/linux/kernel.h	Mon Apr 12 10:53:58 2004
+++ edited/include/linux/kernel.h	Fri May  7 16:16:49 2004
@@ -107,6 +107,7 @@
 }
 
 extern void bust_spinlocks(int yes);
+extern int early_printk_ok;		/* If set, console drivers will be called even if the system isn't up yet */
 extern int oops_in_progress;		/* If set, an oops, panic(), BUG() or die() is in progress */
 extern int panic_on_oops;
 extern int system_state;		/* See values below */

Re: [PATCH] allow console drivers to be called early

[Andrew Morton]

Jesse Barnes <jbarnes@engr.sgi.com> wrote:
>
> This is a simple patch to allow arches to set early_printk_ok if they've 
>  registered console drivers that support early operation.  I've got an ia64 
>  specific bit and an sn2 specific bit that I can post for reference if 
>  anyone's interested, but they're pretty straightforward, so I'm just posting 
>  this for comments.  The ia64 one just adds a register_early_consoles() 
>  function to the ia64 code that gets called early on in setup_arch.  All it 
>  does is call the init routines of console drivers that are setup to do early 
>  printks.
>
> ...
>    * console_sem protects the console_drivers list, and also
>  @@ -526,7 +527,7 @@
>   			log_level_unknown = 1;
>   	}
>   
>  -	if (!cpu_online(smp_processor_id()) &&
>  +	if (!early_printk_ok && !cpu_online(smp_processor_id()) &&

Is it not possible to mark this cpu as being online?   It sure seems to be.

Re: [PATCH] allow console drivers to be called early

[Jesse Barnes]

On Thursday, May 13, 2004 7:44 pm, Andrew Morton wrote:
> >  -	if (!cpu_online(smp_processor_id()) &&
> >  +	if (!early_printk_ok && !cpu_online(smp_processor_id()) &&
>
> Is it not possible to mark this cpu as being online?   It sure seems to be.

But then we miss out on all the good stuff happening in setup_arch since 
smp_processor_id() isn't set in cpu_online_map until smp_prepare_boot_cpu.  I 
can try upping it in arch code, but iirc, I had problems with that in older 
kernels due to the expectations of some of the other CPU upping code.  I'll 
give it a try again and either give you a good answer or send a more 
appropriate patch to David.

Thanks,
Jesse