> -----Original Message----- > From: Henrique de Moraes Holschuh [mailto:hmh@xxxxxxxxxx] > Sent: Friday, September 26, 2014 12:51 AM > To: Chao Yu > Cc: neilb@xxxxxxx; linux-raid@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > Subject: Re: [PATCH] md: avoid potential long delay under pers_lock > > On Thu, 25 Sep 2014, Chao Yu wrote: > > 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@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); > > 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; > > } > > Wouldn't it make more sense to move the printk after the spin_unlock ? As original printk msg in {,un}register_md_personality shows '{,un}registered' which means the main job is done before printk, it's better to move the printk after spin_unlock in both {,un}register_md_personality. But IMHO, it's another minor issue, should we fix in this patch? Thanks, Yu > > -- > "One disk to rule them all, One disk to find them. One disk to bring > them all and in the darkness grind them. In the Land of Redmond > where the shadows lie." -- The Silicon Valley Tarot > Henrique Holschuh -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
