Re: [GIT PULL] SLAB changes for v2.6.39-rc1

[Pekka Enberg <penberg@kernel.org>]

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On Thu, Mar 24, 2011 at 4:41 PM, Christoph Lameter <cl@linux.com> wrote:
> On Thu, 24 Mar 2011, Ingo Molnar wrote:
>
>> FYI, some sort of boot crash has snuck upstream in the last 24 hours:
>>
>>  BUG: unable to handle kernel paging request at ffff87ffc147e020
>>  IP: [<ffffffff811aa762>] this_cpu_cmpxchg16b_emu+0x2/0x1c
>
> Hmmm.. This is the fallback code for the case that the processor does not
> support cmpxchg16b.

How does alternative_io() work? Does it require
alternative_instructions() to be executed. If so, the fallback code
won't be active when we enter kmem_cache_init(). Is there any reason
check_bugs() is called so late during boot? Can we do something like
the totally untested attached patch?

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diff --git a/init/main.c b/init/main.c
index 4a9479e..e57d6a7 100644
--- a/init/main.c
+++ b/init/main.c
@@ -508,6 +508,7 @@ asmlinkage void __init start_kernel(void)
 	vfs_caches_init_early();
 	sort_main_extable();
 	trap_init();
+	check_bugs();
 	mm_init();
 	/*
 	 * Set up the scheduler prior starting any interrupts (such as the
@@ -614,8 +615,6 @@ asmlinkage void __init start_kernel(void)
 	taskstats_init_early();
 	delayacct_init();
 
-	check_bugs();
-
 	acpi_early_init(); /* before LAPIC and SMP init */
 	sfi_init_late();