Messages in this thread Patch in this message | | | Date | Fri, 17 Oct 2008 20:44:51 +0800 | From | "Lai Jiangshan" <> | Subject | Re: [PATCH] x86/proc: fix /proc/cpuinfo cpu offline bug |
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On Fri, Oct 17, 2008 at 7:41 PM, Alexey Dobriyan <adobriyan@gmail.com> wrote: > On Fri, Oct 17, 2008 at 04:55:25PM +0800, Lai Jiangshan wrote: >> In my test, I found that if a cpu has been offline, >> the next cpus may not be shown in the /proc/cpuinfo. >> >> trivially reproduce this bug: >> >> 1) add these lines in the end of show_cpuinfo() >> if (m->size - m->count - 20 > 0) >> seq_printf(m, "%*s", (int)(m->size - m->count - 20), "show bug\n"); > > What is it? > > Can you just show wrong /proc/cpuinfo ? > > Can someone with at least 4-way box please do so?
this is not wrong /proc/cpuinfo, this is an enlarged /proc/cpuinfo this trivial example just use "show bug\n" as the enlarged content.
if you boot your machine with enough cpu, your /proc/cpuinfo have been enlarged too, please use this:
#!/bin/sh nr_cpus=16 # i386 for ((i=1; i<nr_cpus; i++)) do echo 0 > /sys/devices/system/cpu/cpu$i/online cpus=$(grep processor /proc/cpuinfo | wc -l) (( cpus == nr_cpus -1 )) || break; # bug eccur echo 1 > /sys/devices/system/cpu/cpu$i/online done cat /proc/cpuinfo # it shows this bug.
Lai
> >> 3) offline cpu#1 >> 4) cat /proc/cpuinfo >> cpu#2 and cpu#3 .... cannot be shown in /proc/cpuinfo > >> --- a/arch/x86/kernel/cpu/proc.c >> +++ b/arch/x86/kernel/cpu/proc.c >> @@ -160,14 +160,16 @@ 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_online_map); >> - if ((*pos) < nr_cpu_ids && cpu_online(*pos)) >> + else >> + *pos = next_cpu_nr(*pos - 1, cpu_online_map); >> + if ((*pos) < nr_cpu_ids) >> return &cpu_data(*pos); >> return NULL; >> } >> >> static void *c_next(struct seq_file *m, void *v, loff_t *pos) >> { >> - *pos = next_cpu(*pos, cpu_online_map); >> + (*pos)++; >> return c_start(m, pos); >> } > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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