linux/arch/x86/kernel/cpu/proc.c
Lai Jiangshan bc8bcc79ea x86/proc: fix /proc/cpuinfo cpu offline bug
Impact: fix missing CPUs in /proc/cpuinfo after CPU hotunplug/hotreplug

In my test, I found that if a cpu has been offline,
the next cpus may not be shown in the /proc/cpuinfo.

if one read() cannot consume the whole /proc/cpuinfo,
c_start() will be called again in the next read() calls.
And *pos has been increased by 1 by the caller(seq_read()).
if this time the cpu#*pos is offline, c_start() will return
NULL, and the next cpus can not be shown.

this fix use next_cpu_nr(*pos - 1, cpu_online_map) to
search the next unshown cpu.

the most easy way to reproduce this bug:
1) offline cpu#1             (cpu#0 is online)
2) dd ibs=2 if=/proc/cpuinfo
   the result is that only cpu#0 is shown.
   cpu#2 and cpu#3 .... cannot be shown in /proc/cpuinfo
   it's bug.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-22 14:29:37 +02:00

185 lines
4.7 KiB
C

#include <linux/smp.h>
#include <linux/timex.h>
#include <linux/string.h>
#include <linux/seq_file.h>
#include <linux/cpufreq.h>
/*
* Get CPU information for use by the procfs.
*/
#ifdef CONFIG_X86_32
static void show_cpuinfo_core(struct seq_file *m, struct cpuinfo_x86 *c,
unsigned int cpu)
{
#ifdef CONFIG_X86_HT
if (c->x86_max_cores * smp_num_siblings > 1) {
seq_printf(m, "physical id\t: %d\n", c->phys_proc_id);
seq_printf(m, "siblings\t: %d\n",
cpus_weight(per_cpu(cpu_core_map, cpu)));
seq_printf(m, "core id\t\t: %d\n", c->cpu_core_id);
seq_printf(m, "cpu cores\t: %d\n", c->booted_cores);
seq_printf(m, "apicid\t\t: %d\n", c->apicid);
seq_printf(m, "initial apicid\t: %d\n", c->initial_apicid);
}
#endif
}
static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c)
{
/*
* We use exception 16 if we have hardware math and we've either seen
* it or the CPU claims it is internal
*/
int fpu_exception = c->hard_math && (ignore_fpu_irq || cpu_has_fpu);
seq_printf(m,
"fdiv_bug\t: %s\n"
"hlt_bug\t\t: %s\n"
"f00f_bug\t: %s\n"
"coma_bug\t: %s\n"
"fpu\t\t: %s\n"
"fpu_exception\t: %s\n"
"cpuid level\t: %d\n"
"wp\t\t: %s\n",
c->fdiv_bug ? "yes" : "no",
c->hlt_works_ok ? "no" : "yes",
c->f00f_bug ? "yes" : "no",
c->coma_bug ? "yes" : "no",
c->hard_math ? "yes" : "no",
fpu_exception ? "yes" : "no",
c->cpuid_level,
c->wp_works_ok ? "yes" : "no");
}
#else
static void show_cpuinfo_core(struct seq_file *m, struct cpuinfo_x86 *c,
unsigned int cpu)
{
#ifdef CONFIG_SMP
if (c->x86_max_cores * smp_num_siblings > 1) {
seq_printf(m, "physical id\t: %d\n", c->phys_proc_id);
seq_printf(m, "siblings\t: %d\n",
cpus_weight(per_cpu(cpu_core_map, cpu)));
seq_printf(m, "core id\t\t: %d\n", c->cpu_core_id);
seq_printf(m, "cpu cores\t: %d\n", c->booted_cores);
seq_printf(m, "apicid\t\t: %d\n", c->apicid);
seq_printf(m, "initial apicid\t: %d\n", c->initial_apicid);
}
#endif
}
static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c)
{
seq_printf(m,
"fpu\t\t: yes\n"
"fpu_exception\t: yes\n"
"cpuid level\t: %d\n"
"wp\t\t: yes\n",
c->cpuid_level);
}
#endif
static int show_cpuinfo(struct seq_file *m, void *v)
{
struct cpuinfo_x86 *c = v;
unsigned int cpu = 0;
int i;
#ifdef CONFIG_SMP
cpu = c->cpu_index;
#endif
seq_printf(m, "processor\t: %u\n"
"vendor_id\t: %s\n"
"cpu family\t: %d\n"
"model\t\t: %u\n"
"model name\t: %s\n",
cpu,
c->x86_vendor_id[0] ? c->x86_vendor_id : "unknown",
c->x86,
c->x86_model,
c->x86_model_id[0] ? c->x86_model_id : "unknown");
if (c->x86_mask || c->cpuid_level >= 0)
seq_printf(m, "stepping\t: %d\n", c->x86_mask);
else
seq_printf(m, "stepping\t: unknown\n");
if (cpu_has(c, X86_FEATURE_TSC)) {
unsigned int freq = cpufreq_quick_get(cpu);
if (!freq)
freq = cpu_khz;
seq_printf(m, "cpu MHz\t\t: %u.%03u\n",
freq / 1000, (freq % 1000));
}
/* Cache size */
if (c->x86_cache_size >= 0)
seq_printf(m, "cache size\t: %d KB\n", c->x86_cache_size);
show_cpuinfo_core(m, c, cpu);
show_cpuinfo_misc(m, c);
seq_printf(m, "flags\t\t:");
for (i = 0; i < 32*NCAPINTS; i++)
if (cpu_has(c, i) && x86_cap_flags[i] != NULL)
seq_printf(m, " %s", x86_cap_flags[i]);
seq_printf(m, "\nbogomips\t: %lu.%02lu\n",
c->loops_per_jiffy/(500000/HZ),
(c->loops_per_jiffy/(5000/HZ)) % 100);
#ifdef CONFIG_X86_64
if (c->x86_tlbsize > 0)
seq_printf(m, "TLB size\t: %d 4K pages\n", c->x86_tlbsize);
#endif
seq_printf(m, "clflush size\t: %u\n", c->x86_clflush_size);
#ifdef CONFIG_X86_64
seq_printf(m, "cache_alignment\t: %d\n", c->x86_cache_alignment);
seq_printf(m, "address sizes\t: %u bits physical, %u bits virtual\n",
c->x86_phys_bits, c->x86_virt_bits);
#endif
seq_printf(m, "power management:");
for (i = 0; i < 32; i++) {
if (c->x86_power & (1 << i)) {
if (i < ARRAY_SIZE(x86_power_flags) &&
x86_power_flags[i])
seq_printf(m, "%s%s",
x86_power_flags[i][0]?" ":"",
x86_power_flags[i]);
else
seq_printf(m, " [%d]", i);
}
}
seq_printf(m, "\n\n");
return 0;
}
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);
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)++;
return c_start(m, pos);
}
static void c_stop(struct seq_file *m, void *v)
{
}
const struct seq_operations cpuinfo_op = {
.start = c_start,
.next = c_next,
.stop = c_stop,
.show = show_cpuinfo,
};