Re: [BUG] next-20081216 - WARNING: at kernel/smp.c:333 smp_call_function_mask

Ingo Molnar
2008-12-26T18:19:06Z

* Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> wrote:

> > how about the patch below, does that work too? (after removing
> > Yinghai's patch)
>
> Hi Ingo,
>
> Kernel crashes with the same trace, after the applying the patch.

okay, thanks - does the below cleaner variant of Yinghai's patch solve the
problem too?

Ingo

-------------------->
>From 9c93fc72ec95dc97d65b840978f9d605f4e5823a Mon Sep 17 00:00:00 2001
From: Yinghai Lu <yinghai@kernel.org>
Date: Fri, 26 Dec 2008 02:05:47 -0800
Subject: [PATCH] sparseirq: work around compiler optimizing away __weak functions

Impact: fix panic on null pointer with sparseirq

Some GCC versions seem to inline the weak global function,
when that function is empty.

Work it around, by putting a barrier into the function.

Signed-off-by: Yinghai <yinghai@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
init/main.c | 9 +++++++++
kernel/irq/handle.c | 3 ++-
2 files changed, 11 insertions(+), 1 deletions(-)

diff --git a/init/main.c b/init/main.c
index c1f999a..841d2b2 100644
--- a/init/main.c
+++ b/init/main.c
@@ -531,20 +531,29 @@ static void __init boot_cpu_init(void)
cpu_set(cpu, cpu_possible_map);
}

+/*
+ * The barriers are needed to keep a GCC bug from optimizing
+ * away these weak functions:
+ */
+
void __init __weak smp_setup_processor_id(void)
{
+ barrier();
}

void __init __weak thread_info_cache_init(void)
{
+ barrier();
}

void __init __weak arch_early_irq_init(void)
{
+ barrier();
}

void __init __weak early_irq_init(void)
{
+ barrier();
arch_early_irq_init();
}

diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index 06b05a4..a6d16a4 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -86,8 +86,9 @@ void init_kstat_irqs(struct irq_desc *desc, int cpu, int nr)
desc->kstat_irqs = (unsigned int *)ptr;
}

-void __attribute__((weak)) arch_init_chip_data(struct irq_desc *desc, int cpu)
+void __weak arch_init_chip_data(struct irq_desc *desc, int cpu)
{
+ barrier();
}

static void init_one_irq_desc(int irq, struct irq_desc *desc, int cpu)