Re: [ACPI] acpi_bus_register_driver() returns -ENODEV after resume

I've received some feedback about problems loading the asus_acpi driver
back after swsusp resume. I managed to hit that problem on a 2.4.21 +
20030619 ACPI + swsusp1.1-rc2. I don't know yet if it is present in more
recent versions, since this behaviour is not common (at least on my
machine). Usually, the module can be loaded and unloaded without problems.

Anyway, judging on my quick glance at the code, it would seem that something
disables acpi (i.e. sets acpi_disabled to a non-zero value) somewhere
during the suspend / resume cycle, which in turn causes
acpi_bus_register_driver to return -ENODEV. Is my reasoning correct, or am
I missing some codepath? If not, it would signify a bug in ACPI / swsusp
interaction. I'll try yet to hit this on a recent kernel.

It's obscure, but I think I know the answer. From arch/i386/kernel/setup.c: 

#ifdef  CONFIG_ACPI
        int acpi_disabled __initdata = 0;
#else
        int acpi_disabled __initdata = 1;
#endif
EXPORT_SYMBOL(acpi_disabled);


Since it's __initdata, the memory will be freed early in the init process 
(c.f. init/main.c::init() -> free_initmem()). Anything that uses it later 
is touching memory that is either unallocated, or allocated by something 
else. That's a bug. 

Also, it doesn't need to be EXPORTed. If it is left as initdata, that's
another bug, because the two are semantically disjoint. However, even with
the patch below, I'm not sure why you would want to expose the variable 
(and I've in fact removed that). 

Please give it a try and let me know if helps. 


Tangential question: Do preprocessor conditionals evaluate to a value? 
I.e. instead of doing: 

#ifdef	CONFIG_ACPI
	int acpi_disabled = 0;
#else
	int acpi_disabled = 1;
#endif

Could we do: 

int acpi_disabled = (CONFIG_ACPI == 'y'); 

..or something? 

Thanks,


	Pat

===== arch/i386/kernel/setup.c 1.95 vs edited =====

--- 1.95/arch/i386/kernel/setup.c	Sun Aug 31 16:14:11 2003
+++ edited/arch/i386/kernel/setup.c	Tue Sep  2 15:35:00 2003

@@ -64,11 +64,10 @@
 EXPORT_SYMBOL_GPL(mmu_cr4_features);
 
 #ifdef	CONFIG_ACPI
-	int acpi_disabled __initdata = 0;
+	int acpi_disabled = 0;
 #else
-	int acpi_disabled __initdata = 1;
+	int acpi_disabled = 1;
 #endif
-EXPORT_SYMBOL(acpi_disabled);
 
 #ifdef	CONFIG_ACPI_BOOT
 	int acpi_irq __initdata = 1;	/* enable IRQ */



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