Messages in this thread | | | Date | Thu, 31 Aug 2017 23:24:13 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: WARNING: possible circular locking dependency detected |
| |
On Thu, 31 Aug 2017, Thomas Gleixner wrote: > On Thu, 31 Aug 2017, Peter Zijlstra wrote: > > > On Thu, Aug 31, 2017 at 09:55:57AM +0200, Thomas Gleixner wrote: > > > > Arghh!!! > > > > > > > > And allowing us to create events for offline CPUs (possible I think, but > > > > maybe slightly tricky) won't solve that, because we're already holding > > > > the hotplug_lock during PREPARE. > > > > > > There are two ways to cure that: > > > > > > 1) Have a pre cpus_write_lock() stage which is serialized via > > > cpus_add_remove_lock, which is the outer lock for hotplug. > > > > > > There we can sanely create stuff and fail with all consequences. > > > > True, if you're willing to add more state to that hotplug thing I'll try > > and make that perf patch that allows attaching to offline CPUs. > > Now that I think more about it. That's going to be an interesting exercise > vs. the hotplug state registration which relies on cpus_read_lock() > serialization.....
We could have that for built-in stuff which is guaranteed to be never unregistered. Pretty restricted, but for cases like that it could work. Famous last work ...
Thanks,
tglx
| |