[PATCH] md: avoid potential long delay under pers_lock

From: Chao Yu
Date: Thu Sep 25 2014 - 03:29:23 EST

printk may cause long time lapse if value of printk_delay in sysctl is
configured large by user. If register_md_personality takes long time to print in
spinlock pers_lock, we may encounter high CPU usage rate when there are other
pers_lock competitors who may be blocked to spin.
We can avoid this condition by moving printk out of coverage of pers_lock

Signed-off-by: Chao Yu <chao2.yu@xxxxxxxxxxx>
drivers/md/md.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index e02de05..5fcf215 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7200,9 +7200,10 @@ static const struct file_operations md_seq_fops = {

int register_md_personality(struct md_personality *p)
+ printk(KERN_INFO "md: %s personality registered for level %d\n",
+ p->name, p->level);
list_add_tail(&p->list, &pers_list);
- printk(KERN_INFO "md: %s personality registered for level %d\n", p->name, p->level);
return 0;

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