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

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Date:	Sun, 28 Dec 2008 16:53:02 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
Subject: Re: [git pull] sparseirq / irq updates for v2.6.29

Yinghai Lu wrote:
> Ingo Molnar wrote:
>> * Ingo Molnar <mingo@...e.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@...e.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
> 
> 

or this one

[PATCH] sparseirq: move weak function to chip.c v2

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@...nel.org>

---
 init/main.c         |    4 ++++
 kernel/irq/chip.c   |    5 +++++
 kernel/irq/handle.c |    5 -----
 3 files changed, 9 insertions(+), 5 deletions(-)

Index: linux-2.6/init/main.c
===================================================================
--- linux-2.6.orig/init/main.c
+++ linux-2.6/init/main.c
@@ -544,11 +544,15 @@ void __init __weak thread_info_cache_ini
 
 int __init __weak arch_early_irq_init(void)
 {
+	printk(KERN_DEBUG "calling __weak arch_early_irq_init()\n");
+
 	return 0;
 }
 
 int __init __weak early_irq_init(void)
 {
+	printk(KERN_DEBUG "calling __weak early_irq_init()\n");
+
 	return arch_early_irq_init();
 }
 
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 +18,11 @@
 
 #include "internals.h"
 
+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));
--
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