On Tue, Jun 21, 2016 at 11:36:51AM -0400, Tejun Heo wrote: > On Tue, Jun 21, 2016 at 07:42:31PM +0530, Gautham R Shenoy wrote: > > > Subject: [PATCH] sched: allow kthreads to fallback to online && !active > > > cpus > > > > > > During CPU hotplug, CPU_ONLINE callbacks are run while the CPU is > > > online but not active. A CPU_ONLINE callback may create or bind a > > > kthread so that its cpus_allowed mask only allows the CPU which is > > > being brought online. The kthread may start executing before the CPU > > > is made active and can end up in select_fallback_rq(). > > > > > > In such cases, the expected behavior is selecting the CPU which is > > > coming online; however, because select_fallback_rq() only chooses from > > > active CPUs, it determines that the task doesn't have any viable CPU > > > in its allowed mask and ends up overriding it to cpu_possible_mask. > > > > > > CPU_ONLINE callbacks should be able to put kthreads on the CPU which > > > is coming online. Update select_fallback_rq() so that it follows > > > cpu_online() rather than cpu_active() for kthreads. > > > > > > Signed-off-by: Tejun Heo <t...@kernel.org> > > > Reported-by: Gautham R Shenoy <e...@linux.vnet.ibm.com> > > > > Hi Tejun, > > > > This patch fixes the issue on POWER. I am able to see the worker > > threads of the unbound workqueues of the newly onlined node with this. > > > > Tested-by: Gautham R. Shenoy <e...@linux.vnet.ibm.com> > > Peter?
Hurm.. So I've applied it, just to get this issue sorted, but I'm not entirely sure I like it. I think I prefer ego's version because that makes it harder to get stuff to run on !active,online cpus. I think we really want to be careful what gets to run during that state. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
