On Tue, Feb 07, 2017 at 10:42:49AM +0000, Mel Gorman wrote: > On Tue, Feb 07, 2017 at 10:23:31AM +0100, Vlastimil Babka wrote: > > > cpu offlining. I have to check the code but my impression was that WQ > > > code will ignore the cpu requested by the work item when the cpu is > > > going offline. If the offline happens while the worker function already > > > executes then it has to wait as we run with preemption disabled so we > > > should be safe here. Or am I missing something obvious? > > > > Tejun suggested an alternative solution to avoiding get_online_cpus() in > > this thread: > > https://lkml.kernel.org/r/<[email protected]> > > But it would look like the following as it could be serialised against > pcpu_drain_mutex as the cpu hotplug teardown callback is allowed to sleep. >
Bah, this is obviously unsafe. It's guaranteed to deadlock. -- Mel Gorman SUSE Labs
