Messages in this thread | | | Date | Wed, 30 Nov 2011 20:06:31 -0600 | From | Dimitri Sivanich <> | Subject | Re: [PATCH] specific do_timer_cpu value for nohz off mode |
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On Wed, Nov 30, 2011 at 04:11:31PM -0800, Andrew Morton wrote: > On Wed, 30 Nov 2011 09:29:59 -0600 > Dimitri Sivanich <sivanich@sgi.com> wrote: > > > +static ssize_t sysfs_store_do_timer_cpu(struct sys_device *dev, > > + struct sysdev_attribute *attr, > > + const char *buf, size_t size) > > +{ > > + struct sysdev_ext_attribute *ea = SYSDEV_TO_EXT_ATTR(attr); > > + unsigned int new; > > + int rv; > > + > > +#ifdef CONFIG_NO_HZ > > + /* nohz mode not supported */ > > + if (tick_nohz_enabled) > > + return -EINVAL; > > +#endif > > + > > + rv = kstrtouint(buf, 0, &new); > > + if (rv) > > + return rv; > > + > > + if (new >= NR_CPUS || !cpu_online(new)) > > + return -ERANGE; > > + > > + *(unsigned int *)(ea->var) = new; > > + return size; > > +} > > checkpatch tells us: > > WARNING: usage of NR_CPUS is often wrong - consider using cpu_possible(), num_possible_cpus(), for_each_possible_cpu(), etc
I think a check against num_possible_cpus() should be OK.
> > I think the check can just be removed? Surely cpu_online(1000000000) > will return false?
A value > NR_CPUS and < MAX_INT caused a panic in sysfs_store_do_timer_cpu, presumably from the cpu_online() check. The check against NR_CPUS avoided the panic.
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