linux-kernel - Re: [PATCH] ARCH: Fix 32-bit x86 MSI-X allocation leakage

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Date:	Mon, 28 Apr 2008 22:30:25 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	PJ Waskiewicz <peter.p.waskiewicz.jr@...el.com>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>, netdev@...r.kernel.org
Subject: Re: [PATCH] ARCH: Fix 32-bit x86 MSI-X allocation leakage

On Fri, 25 Apr 2008, PJ Waskiewicz wrote:
> This bug was introduced in the 2.6.24 i386/x86_64 tree merge, where

Can you please explain what exactly caused the bug. Definitely not the
move from arch/i386 to arch/x86 as the code there was not changed at
all and has not be changed since then.

CC'ed Eric as well.

Thanks
	tglx


> MSI-X vector allocation will eventually fail.  The cause is the new
> bit array tracking used vectors is not getting cleared properly on
> IRQ destruction on the 32-bit APIC code.
> 
> This can be seen easily using the ixgbe 10 GbE driver on multi-core
> systems by simply loading and unloading the driver a few times.
> Depending on the number of available vectors on the host system, the
> MSI-X allocation will eventually fail, and the driver will only be
> able to use legacy interrupts.
> 
> I am generating the same patch for both stable trees for 2.6.24 and
> 2.6.25.
> 
> Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>
> ---
> 
>  arch/x86/kernel/io_apic_32.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> 
> diff --git a/arch/x86/kernel/io_apic_32.c b/arch/x86/kernel/io_apic_32.c
> index 2e2f420..77798b1 100644
> --- a/arch/x86/kernel/io_apic_32.c
> +++ b/arch/x86/kernel/io_apic_32.c
> @@ -2444,6 +2444,7 @@ void destroy_irq(unsigned int irq)
>  	dynamic_irq_cleanup(irq);
>  
>  	spin_lock_irqsave(&vector_lock, flags);
> +	clear_bit(irq_vector[irq], used_vectors);
>  	irq_vector[irq] = 0;
>  	spin_unlock_irqrestore(&vector_lock, flags);
>  }
> 
> --
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