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

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Date:	Mon, 29 Dec 2008 10:52:44 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Yinghai Lu <yinghai@...nel.org>
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


* Ingo Molnar <mingo@...e.hu> wrote:

> By far the best solution is to move them into a different compilation 
> unit - i.e. your first patch - i'll apply that one.

your patch didnt apply, and it also missed the following detail: 
kernel/irq/ is only included on genirq architectures - not on some others. 
So i ended up with the refactored patch below.

	Ingo

---------------->
>From 18aa3101b32c90738182dba89d43f7c984e90e82 Mon Sep 17 00:00:00 2001
From: Yinghai Lu <yhlu.kernel@...il.com>
Date: Sun, 28 Dec 2008 16:01:13 -0800
Subject: [PATCH] sparseirq: move __weak symbols into separate compilation unit

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.

So move all the IRQ handling related __weak symbols to kernel/irq/chip.c.

Signed-off-by: Yinghai Lu <yinghai@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 init/main.c         |   10 ----------
 kernel/irq/manage.c |    9 ---------
 kernel/softirq.c    |   20 ++++++++++++++++++++
 3 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/init/main.c b/init/main.c
index c314aa1..2c183ab 100644
--- a/init/main.c
+++ b/init/main.c
@@ -539,16 +539,6 @@ 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();
-}
-
 asmlinkage void __init start_kernel(void)
 {
 	char * command_line;
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index c2741b0..46953a0 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -261,15 +261,6 @@ void enable_irq(unsigned int irq)
 }
 EXPORT_SYMBOL(enable_irq);
 
-/*
- * [ Not in kernel/irq/handle.c, so that GCC does not
- *   inline the __weak alias: ]
- */
-int __weak arch_init_chip_data(struct irq_desc *desc, int cpu)
-{
-	return 0;
-}
-
 static int set_irq_wake_real(unsigned int irq, unsigned int on)
 {
 	struct irq_desc *desc = irq_to_desc(irq);
diff --git a/kernel/softirq.c b/kernel/softirq.c
index e7c69a7..daf4635 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -797,3 +797,23 @@ int on_each_cpu(void (*func) (void *info), void *info, int wait)
 }
 EXPORT_SYMBOL(on_each_cpu);
 #endif
+
+/*
+ * [ These __weak aliases are kept in a separate compilation unit, so that
+ *   GCC does not inline them incorrectly. ]
+ */
+
+int __init __weak early_irq_init(void)
+{
+	return 0;
+}
+
+int __init __weak arch_early_irq_init(void)
+{
+	return 0;
+}
+
+int __weak arch_init_chip_data(struct irq_desc *desc, int cpu)
+{
+	return 0;
+}
--
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