2007-11-06 08:37:38

by Zou, Nanhai

Subject: [Patch2/2] fix wrong proc cpuinfo on x64

in 2.6.24-rc1 kernel,
The /proc/cpuinfo display is wrong.

Another issue is that it will display bogus cpus with wrong information
if the kernel is compiled with a big CONFIG_NR_CPU.

That is because before a cpu in cpu_present_map is up, c->cpu_index of
that cpu is 0.
thus the cpu_online(c->cpu_index) check in show_cpuinfo is invalid.

This patch will let cpuinfo_op use cpu_online_map instead of
cpu_present_map to iterate cpus.


Signed-off-by: Zou Nan hai <[email protected]>

--- linux-2.6.24-rc1/arch/x86/kernel/setup_64.c 2007-10-29 22:03:05.000000000 -0400
+++ b/arch/x86/kernel/setup_64.c 2007-11-05 23:09:06.000000000 -0500
@@ -1078,8 +1078,6 @@ static int show_cpuinfo(struct seq_file


#ifdef CONFIG_SMP
- if (!cpu_online(c->cpu_index))
- return 0;
cpu = c->cpu_index;
#endif

@@ -1171,15 +1169,15 @@ static int show_cpuinfo(struct seq_file
static void *c_start(struct seq_file *m, loff_t *pos)
{
if (*pos == 0) /* just in case, cpu 0 is not the first */
- *pos = first_cpu(cpu_possible_map);
- if ((*pos) < NR_CPUS && cpu_possible(*pos))
+ *pos = first_cpu(cpu_online_map);
+ if ((*pos) < NR_CPUS && cpu_online(*pos))
return &cpu_data(*pos);
return NULL;
}

static void *c_next(struct seq_file *m, void *v, loff_t *pos)
{
- *pos = next_cpu(*pos, cpu_possible_map);
+ *pos = next_cpu(*pos, cpu_online_map);
return c_start(m, pos);
}

2007-11-06 18:38:14

by tip-bot for Andreas Herrmann

Subject: Re: [Patch2/2] fix wrong proc cpuinfo on x64

On Tue, Nov 06, 2007 at 04:28:20PM +0800, Zou Nan hai wrote:
> in 2.6.24-rc1 kernel,
> The /proc/cpuinfo display is wrong.
>
> Another issue is that it will display bogus cpus with wrong information
> if the kernel is compiled with a big CONFIG_NR_CPU.
>
> That is because before a cpu in cpu_present_map is up, c->cpu_index of
> that cpu is 0.
> thus the cpu_online(c->cpu_index) check in show_cpuinfo is invalid.

This issue should already be fixed with that patch

http://marc.info/?l=linux-kernel&m=119394201230954

> This patch will let cpuinfo_op use cpu_online_map instead of
> cpu_present_map to iterate cpus.

BTW, the problem affects i386 as well.


Regards,

Andreas

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