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authorLai Jiangshan <laijs@cn.fujitsu.com>2008-10-22 12:42:30 +0800
committerIngo Molnar <mingo@elte.hu>2008-10-22 14:29:37 +0200
commitbc8bcc79ea4203c7d04309f1307ab88c86f0b0cf (patch)
tree4aa34a173e9562cacb51ef7e7d175a68b4415f8a /arch
parent35af28219e684a36cc8b1ff456c370ce22be157d (diff)
downloadlinux-bc8bcc79ea4203c7d04309f1307ab88c86f0b0cf.tar.gz
linux-bc8bcc79ea4203c7d04309f1307ab88c86f0b0cf.tar.xz
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/cpu/proc.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index a26c480b9491..01b1244ef1c0 100644
--- 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);
}