Re: [PATCH v2 12/14] torture: Replace cpu_up/down with device_online/offline

[Qais Yousef]

On 11/28/19 16:56, Qais Yousef wrote:
> On 11/27/19 13:47, Paul E. McKenney wrote:
> > On Mon, Nov 25, 2019 at 11:27:52AM +0000, Qais Yousef wrote:
> > > The core device API performs extra housekeeping bits that are missing
> > > from directly calling cpu_up/down.
> > > 
> > > See commit a6717c01ddc2 ("powerpc/rtas: use device model APIs and
> > > serialization during LPM") for an example description of what might go
> > > wrong.
> > > 
> > > This also prepares to make cpu_up/down a private interface for anything
> > > but the cpu subsystem.
> > > 
> > > Signed-off-by: Qais Yousef <qais.yousef@xxxxxxx>
> > > CC: Davidlohr Bueso <dave@xxxxxxxxxxxx>
> > > CC: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
> > > CC: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> > > CC: linux-kernel@xxxxxxxxxxxxxxx
> > 
> > Looks fine from an rcutorture viewpoint, but why not provide an API
> > that pulled lock_device_hotplug() and unlock_device_hotplug() into the
> > online/offline calls?
> 
> I *think* the right way to do what you say is by doing lock_device_hotplug()
> inside device_{online, offline}() - which affects all drivers not just the CPU.
> 
> And even then, I think we need to refcount it so nested calls won't deadlock.

Forget that. I don't think nesting here makes actually any sense.

Thanks

--
Qais Yousef