linux-kernel - Re: [PATCH] [irq] Fix boot failure when irqaffinity is passed.

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Date:   Tue, 31 Oct 2017 12:29:46 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Rakib Mullick <rakib.mullick@...il.com>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH]  [irq] Fix boot failure when irqaffinity is passed.


* Rakib Mullick <rakib.mullick@...il.com> wrote:

> When irqaffinity kernel param is passed in a CPUMASK_OFFSTACK=y build
> kernel, it fails to boot. zalloc_cpumask_var() cannot be used before
> initializing mm stuff (slab allocator) to allocate cpumask. So, use
> alloc_bootmem_cpumask_var(). Also in init_irq_default_affinity() removes
> unneeded ifdef, these ifdef conditions are handled at defination site.
> 
> Signed-off-by: Rakib Mullick <rakib.mullick@...il.com>
> ---
>  kernel/irq/irqdesc.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
> index 982a357..db6380d 100644
> --- a/kernel/irq/irqdesc.c
> +++ b/kernel/irq/irqdesc.c
> @@ -27,7 +27,7 @@ static struct lock_class_key irq_desc_lock_class;
>  #if defined(CONFIG_SMP)
>  static int __init irq_affinity_setup(char *str)
>  {
> -	zalloc_cpumask_var(&irq_default_affinity, GFP_NOWAIT);
> +	alloc_bootmem_cpumask_var(&irq_default_affinity);
>  	cpulist_parse(str, irq_default_affinity);
>  	/*
>  	 * Set at least the boot cpu. We don't want to end up with
> @@ -40,10 +40,8 @@ __setup("irqaffinity=", irq_affinity_setup);
>  
>  static void __init init_irq_default_affinity(void)
>  {
> -#ifdef CONFIG_CPUMASK_OFFSTACK
>  	if (!irq_default_affinity)
>  		zalloc_cpumask_var(&irq_default_affinity, GFP_NOWAIT);
> -#endif
>  	if (cpumask_empty(irq_default_affinity))
>  		cpumask_setall(irq_default_affinity);
>  }

Not applied, because this patch causes the following build warning:

  kernel/irq/irqdesc.c:43:6: warning: the address of ‘irq_default_affinity’ will always evaluate as ‘true’ [-Waddress]

Also, please pick up the improved changelog below for the next version of the 
patch.

Thanks,

	Ingo

===============>
>From 57b19413bbe77f0da6f161a5b2b68a73b42ba157 Mon Sep 17 00:00:00 2001
From: Rakib Mullick <rakib.mullick@...il.com>
Date: Thu, 26 Oct 2017 10:58:00 +0600
Subject: [PATCH] irq/core: Fix boot crash when the irqaffinity= boot parameter is passed on CPUMASK_OFFSTACK=y kernels

When the irqaffinity= kernel parameter is passed in a CPUMASK_OFFSTACK=y
kernel, it fails to boot, because zalloc_cpumask_var() cannot be used before
initializing the slab allocator to allocate a cpumask.

So, use alloc_bootmem_cpumask_var() instead.

Also do some cleanups while at it: in init_irq_default_affinity() remove
an unnecessary #ifdef.

Signed-off-by: Rakib Mullick <rakib.mullick@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/20171026045800.27087-1-rakib.mullick@gmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/irq/irqdesc.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 982a3576fb01..db6380d4517d 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -27,7 +27,7 @@ static struct lock_class_key irq_desc_lock_class;
 #if defined(CONFIG_SMP)
 static int __init irq_affinity_setup(char *str)
 {
-	zalloc_cpumask_var(&irq_default_affinity, GFP_NOWAIT);
+	alloc_bootmem_cpumask_var(&irq_default_affinity);
 	cpulist_parse(str, irq_default_affinity);
 	/*
 	 * Set at least the boot cpu. We don't want to end up with
@@ -40,10 +40,8 @@ __setup("irqaffinity=", irq_affinity_setup);
 
 static void __init init_irq_default_affinity(void)
 {
-#ifdef CONFIG_CPUMASK_OFFSTACK
 	if (!irq_default_affinity)
 		zalloc_cpumask_var(&irq_default_affinity, GFP_NOWAIT);
-#endif
 	if (cpumask_empty(irq_default_affinity))
 		cpumask_setall(irq_default_affinity);
 }