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

Yinghai Lu
2008-12-29T00:29:20Z

Ingo Molnar 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.

that is not enough.

need

[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>

---
init/main.c | 9 +++------
kernel/irq/chip.c | 10 ++++++++++
kernel/irq/handle.c | 5 -----
3 files changed, 13 insertions(+), 11 deletions(-)

Index: linux-2.6/init/main.c
===================================================================
--- linux-2.6.orig/init/main.c
+++ linux-2.6/init/main.c
@@ -542,14 +542,11 @@ void __init __weak thread_info_cache_ini
{
}

-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)
Index: linux-2.6/kernel/irq/chip.c
===================================================================
--- linux-2.6.orig/kernel/irq/chip.c
+++ linux-2.6/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
Index: linux-2.6/kernel/irq/handle.c
===================================================================
--- linux-2.6.orig/kernel/irq/handle.c
+++ linux-2.6/kernel/irq/handle.c
@@ -86,11 +86,6 @@ void init_kstat_irqs(struct irq_desc *de
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));