linux-kernel - Re: [PATCH] prevent powerpc from invoking irq handlers on offline CPUs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1220229284.13162.411.camel@pasglop>
Date:	Mon, 01 Sep 2008 10:34:44 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	paulmck@...ux.vnet.ibm.com
Cc:	linux-kernel@...r.kernel.org, paulus@...ba.org,
	jwboyer@...ux.vnet.ibm.com, tnt@...tNt.com,
	grant.likely@...retlab.ca, linuxppc-dev@...abs.org,
	manfred@...orfullife.com, akpm@...ux-foundation.org
Subject: Re: [PATCH] prevent powerpc from invoking irq handlers on offline
	CPUs

On Sun, 2008-08-31 at 10:31 -0700, Paul E. McKenney wrote:
> Make powerpc refrain from clearing a given to-be-offlined CPU's bit in the
> cpu_online_mask until it has processed pending irqs.  This change
> prevents other CPUs from being blindsided by an apparently offline CPU
> nevertheless changing globally visible state.
> 
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> ---

Sounds reasonable... the only possible worry here is if somebody tries
an IPI ... The IPI code will and the target CPU mask with the online
map, so it may try to send to the to-be-offlined CPU and timeout, no ?

Cheers,
Ben.

>  smp.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 5337ca7..1fedd7d 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -250,11 +250,11 @@ int generic_cpu_disable(void)
>  	if (cpu == boot_cpuid)
>  		return -EBUSY;
>  
> -	cpu_clear(cpu, cpu_online_map);
>  #ifdef CONFIG_PPC64
>  	vdso_data->processorCount--;
>  	fixup_irqs(cpu_online_map);
>  #endif
> +	cpu_clear(cpu, cpu_online_map);
>  	return 0;
>  }
>  

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/