Re: kernel/workqueue.c:4434:61: sparse: expression using sizeof bool

Re: kernel/workqueue.c:4434:61: sparse: expression using sizeof bool

[Fengguang Wu]

CC Christopher and LKML.

On Wed, Apr 03, 2013 at 02:57:18PM -0700, Tejun Heo wrote:
> Hello, Fengguang.

Hi Tejun!

> On Sat, Mar 30, 2013 at 08:29:47PM +0800, kbuild test robot wrote:
> > tree:   git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git review-better-dbg
> > head:   ea44ca757342b769c176fd6d0b3fb525b22eeda9
> > commit: c04655aeae70173688bca4c62b35737ab6958e82 workqueue: include workqueue info when printing debug dump of a worker task
> > date:   10 hours ago
> > 
> > 
> > sparse warnings: (new ones prefixed by >>)
> > 
> >    kernel/workqueue.c:287:8: sparse: symbol 'cpu_worker_pools' was not declared. Should it be static?
> >    kernel/workqueue.c:300:25: sparse: symbol 'system_highpri_wq' was not declared. Should it be static?
> > >> kernel/workqueue.c:4434:61: sparse: expression using sizeof bool
> >    kernel/workqueue.c:2060:32: sparse: context imbalance in 'manage_workers' - unexpected unlock
> > 
> > vim +4434 kernel/workqueue.c
> > 
> ...
> >   4433		/* copy worker description */
> > > 4434		probe_kernel_read(&desc_valid, &worker->desc_valid, sizeof(desc_valid));
> >   4435		if (desc_valid)
> 
> I don't know what to make of this warning.  Yes, it's probing a bool
> variable and of course using sizeof(bool) to do that.  Why does sparse
> complain about this?

I guess sparse warns on sizeof(bool) because it is compiler defined.
It may be 1, 4, or even 8 depending on the gcc version and platform.

Thanks,
Fengguang

Re: kernel/workqueue.c:4434:61: sparse: expression using sizeof bool

[Tejun Heo]

Hey,

On Thu, Apr 04, 2013 at 09:42:09AM +0800, Fengguang Wu wrote:
> > >   4433		/* copy worker description */
> > > > 4434		probe_kernel_read(&desc_valid, &worker->desc_valid, sizeof(desc_valid));
> > >   4435		if (desc_valid)
> > 
> > I don't know what to make of this warning.  Yes, it's probing a bool
> > variable and of course using sizeof(bool) to do that.  Why does sparse
> > complain about this?
> 
> I guess sparse warns on sizeof(bool) because it is compiler defined.
> It may be 1, 4, or even 8 depending on the gcc version and platform.

Yeah, it's copying out a bool so as long as that's the actual size,
it's okay.  I mean, it's not like sizeof(long) is constant across
platforms.  I'm gonna ignore it but still curious what the warning is
good for.

Thanks.

-- 
tejun