Re: [git pull] sparseirq / irq updates for v2.6.29

["Yinghai Lu" <yhlu.kernel@gmail.com>]

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On Sun, Dec 28, 2008 at 3:30 PM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Ingo Molnar <mingo@elte.hu> wrote:
>
>>   b2e2fe9: sparseirq: work around __weak alias bug
>
> here's that fix, standalone too. Kamalesh, i think this should finally fix
> the crash you are seeing.
>
>        Ingo
>
> ---------------->
> From b2e2fe99628c4f944c3075258e536197b5a4f3f8 Mon Sep 17 00:00:00 2001
> From: Ingo Molnar <mingo@elte.hu>
> Date: Mon, 29 Dec 2008 00:16:45 +0100
> Subject: [PATCH] sparseirq: work around __weak alias bug
>
> Impact: fix boot crash if the kernel is built with certain GCC versions
>
> GCC has a bug with __weak alias functions: if the functions are in
> the same compilation unit as their call site, GCC can decide to
> inline them - and thus rob the linker of the opportunity to override
> the weak alias with the real thing.
>
> This can lead to the boot crash reported by Kamalesh Babulal:
>
>  ACPI: Core revision 20080926
>  Setting APIC routing to flat
>  BUG: unable to handle kernel NULL pointer dereference at
>  0000000000000000
>  IP: [<ffffffff8021f9a8>] add_pin_to_irq_cpu+0x14/0x74
>  PGD 0
>  Oops: 0000 [#1] SMP
>  [...]
>
> So move the arch_init_chip_data() function from handle.c to manage.c.
>
> Reported-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
> ---
>  kernel/irq/handle.c |    5 -----
>  kernel/irq/manage.c |    9 +++++++++
>  2 files changed, 9 insertions(+), 5 deletions(-)
>

that is not enough.

please check

need one printk, and move two functions into chip.c

YH

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[PATCH] sparseirq: mvoe two weak functions to chip.c

Impact: fix panic

some gcc compiler will remove the weak global blank function
Linus noted that we could move those function to other unit to workaround it.

try to workaround it:
1. one time path: add printk
2. multi time path: move to chip.c

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

diff --git a/init/main.c b/init/main.c
index d0c5e02..6a7a308 100644
--- a/init/main.c
+++ b/init/main.c
@@ -542,14 +542,11 @@ void __init __weak thread_info_cache_init(void)
 {
 }
 
-int __init __weak arch_early_irq_init(void)
-{
-	return 0;
-}
-
 int __init __weak early_irq_init(void)
 {
-	return arch_early_irq_init();
+	printk(KERN_DEBUG "calling __weak early_irq_init()\n");
+
+	return 0;
 }
 
 asmlinkage void __init start_kernel(void)
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index f63c706..2ba0c84 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -18,6 +18,16 @@
 
 #include "internals.h"
 
+int __init __weak arch_early_irq_init(void)
+{
+	return 0;
+}
+
+int __weak arch_init_chip_data(struct irq_desc *desc, int cpu)
+{
+	return 0;
+}
+
 /**
  *	dynamic_irq_init - initialize a dynamically allocated irq
  *	@irq:	irq number to initialize
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index 157c04c..c20db0b 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -86,11 +86,6 @@ void init_kstat_irqs(struct irq_desc *desc, int cpu, int nr)
 		desc->kstat_irqs = (unsigned int *)ptr;
 }
 
-int __weak arch_init_chip_data(struct irq_desc *desc, int cpu)
-{
-	return 0;
-}
-
 static void init_one_irq_desc(int irq, struct irq_desc *desc, int cpu)
 {
 	memcpy(desc, &irq_desc_init, sizeof(struct irq_desc));