From: Armin Steinhoff <armin@steinhoff.de>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
x86@kernel.org
Subject: Re: io_apic.c --> "nr_ioapics" not initialized !
Date: Thu, 21 Feb 2013 08:30:26 +0100 [thread overview]
Message-ID: <5125CD12.2080002@steinhoff.de> (raw)
In-Reply-To: <alpine.LFD.2.02.1302202336270.22263@ionos>
Thomas Gleixner wrote:
> On Wed, 20 Feb 2013, Armin Steinhoff wrote:
>> after a walk through the module "io_apic.c" in
>> "/usr/src/linux/arch/x86/kernel/apic" I got the impression that the variable
>> "nr_ioapics" is used but isn't initialized !
>> Could it be the source of boot problems ?
> Well no, unless your compiler is silly.
>
> arch/x86/kernel/apic/io_apic.c:int nr_ioapics;
>
> That's initialized to 0
My "silly compiler" does it only during load time ....
--Armin
>
>> Dangerous coding stile in "static struct resource * __init
>> ioapic_setup_resources(int nr_ioapics)" ....
> Though the brilliant brain who decided to name the argument of
> ioapic_setup_resources() the same as a global variable and of course
> the call site of it to do:
>
> ioapic_res = ioapic_setup_resources(nr_ioapics);
>
> Brilliant. Unfortunately that's completely correct C code. Though it's
> confusing as hell and definitely worth to be fixed. Patch below.
>
> Thanks,
>
> tglx
>
> Index: linux-2.6/arch/x86/kernel/apic/io_apic.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/apic/io_apic.c
> +++ linux-2.6/arch/x86/kernel/apic/io_apic.c
> @@ -3637,25 +3637,25 @@ void __init setup_ioapic_dest(void)
>
> static struct resource *ioapic_resources;
>
> -static struct resource * __init ioapic_setup_resources(int nr_ioapics)
> +static struct resource * __init ioapic_setup_resources(int cnt)
> {
> unsigned long n;
> struct resource *res;
> char *mem;
> int i;
>
> - if (nr_ioapics <= 0)
> + if (cnt <= 0)
> return NULL;
>
> n = IOAPIC_RESOURCE_NAME_SIZE + sizeof(struct resource);
> - n *= nr_ioapics;
> + n *= cnt;
>
> mem = alloc_bootmem(n);
> res = (void *)mem;
>
> - mem += sizeof(struct resource) * nr_ioapics;
> + mem += sizeof(struct resource) * cnt;
>
> - for (i = 0; i < nr_ioapics; i++) {
> + for (i = 0; i < cnt; i++) {
> res[i].name = mem;
> res[i].flags = IORESOURCE_MEM | IORESOURCE_BUSY;
> snprintf(mem, IOAPIC_RESOURCE_NAME_SIZE, "IOAPIC %u", i);
>
next prev parent reply other threads:[~2013-02-21 7:30 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-19 3:56 [PATCH RT 0/7] [ANNOUNCE] 3.2.38-rt58-rc1 stable review Steven Rostedt
2013-02-19 3:56 ` [PATCH RT 1/7] x86/32: Use kmap switch for non highmem as well Steven Rostedt
2013-02-19 3:56 ` [PATCH RT 2/7] acpi/rt: Convert acpi_gbl_hardware lock back to a raw_spinlock_t Steven Rostedt
2013-02-19 3:56 ` [PATCH RT 3/7] printk: Fix rq->lock vs logbuf_lock unlock lock inversion Steven Rostedt
2013-02-19 3:56 ` [PATCH RT 4/7] serial: Imx: Fix recursive locking bug Steven Rostedt
2013-02-19 3:56 ` [PATCH RT 5/7] wait-simple: Simple waitqueue implementation Steven Rostedt
2013-02-19 3:56 ` [PATCH RT 6/7] rcutiny: Use simple waitqueue Steven Rostedt
2013-02-20 16:20 ` io_apic.c --> "nr_ioapics" not initialized ! Armin Steinhoff
2013-02-20 21:04 ` Robin Holt
2013-02-20 22:55 ` Thomas Gleixner
2013-02-21 7:30 ` Armin Steinhoff [this message]
2013-02-19 3:56 ` [PATCH RT 7/7] Linux 3.2.38-rt58-rc1 Steven Rostedt
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5125CD12.2080002@steinhoff.de \
--to=armin@steinhoff.de \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rt-users@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox