Re: [PATCH] mm/memcg: Disable task obj_stock for PREEMPT_RT

[Waiman Long]

On 8/3/21 9:40 PM, Waiman Long wrote:
> On 8/3/21 7:21 PM, Thomas Gleixner wrote:
> > To complete the analysis of drain_local_stock(). AFAICT that function
> > can only be called from task context. So what is the purpose of this
> > in_task() conditional there?
> >
> >     if (in_task())
> >            drain_obj_stock(&stock->task_obj);
> I haven't done a full analysis to see if it can be called from task 
> context only. Maybe in_task() check isn't needed, but having it there 
> provides the safety that it will still work in case it can be called 
> from interrupt context. 

After looking at possible call chains that can lead to 
drain_local_stock(), one call chain comes from the allocation of slab 
objects which I had previously determined to be callable from interrupt 
context. So it is prudent to add a in_task() check here.

Cheers,
Longman