From: Andi Kleen <ak@suse.de>
To: Mikael Pettersson <mikpe@csd.uu.se>
Cc: ak@suse.de, linux-kernel@vger.kernel.org
Subject: Re: 2.5.61: x86_64 num_online_cpus() buglet?
Date: Tue, 18 Feb 2003 07:31:11 +0100 [thread overview]
Message-ID: <20030218063111.GA14073@wotan.suse.de> (raw)
In-Reply-To: <200302171751.SAA19069@kim.it.uu.se>
On Mon, Feb 17, 2003 at 06:51:12PM +0100, Mikael Pettersson wrote:
> Andi,
>
> Kernel 2.5.61's include/asm-x86_64/smp.h contains:
>
> extern unsigned long cpu_online_map;
> ...
> extern inline unsigned int num_online_cpus(void)
> {
> return hweight32(cpu_online_map);
> }
>
> and similarly for cpu_callout_map.
>
> hweight32() truncates a 64-bit operand to 32-bits, so either
> - the maps should be int rather than long, or
> - x86_64 needs to define and use a new hweight64(), or
> - CONFIG_NR_CPUS must not exceed 32 on x86_64.
>
> Comments?
You're right - it should use hweight64. Thanks for the headup.
I'll fix it.
Currently the x86-64 port is limited to 8 CPUs because the APIC
drivers don't support cluster mode (yet) and can only talk to 8
local apics, so it isn't that harmful.
-Andi
next prev parent reply other threads:[~2003-02-18 6:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-02-17 17:51 Mikael Pettersson
2003-02-18 6:31 ` Andi Kleen [this message]
2003-02-18 7:27 ` David S. Miller
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