Commit 50bd3774 authored Sep 25, 2014 by Chao Yu Committed by NeilBrown Oct 14, 2014

md: avoid potential long delay under pers_lock



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
spinlock.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: NeilBrown <neilb@suse.de>

parent 0638bb0e

drivers/md/md.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -7187,9 +7187,10 @@ 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);
		spin_lock(&pers_lock);
		list_add_tail(&p->list, &pers_list);
		printk(KERN_INFO "md: %s personality registered for level %d\n", p->name, p->level);
		spin_unlock(&pers_lock);
		return 0;
		}