Re: [RFC v2] perf: Rewrite core context handling

[Peter Zijlstra]

On Fri, Jun 17, 2022 at 03:36:51PM +0200, Peter Zijlstra wrote:
> On Mon, Jun 13, 2022 at 04:35:11PM +0200, Peter Zijlstra wrote:
> > +/* XXX: No need of list now. Convert it to per-cpu variable */
> >  static DEFINE_PER_CPU(struct list_head, cgrp_cpuctx_list);
> 
> Something like so I suppose...
> 

I need this on top to avoid a spat on perf_cgroup_attach()

---


diff --git a/kernel/events/core.c b/kernel/events/core.c
index 0cd81a3ef374..c6b64a48dea6 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -13536,9 +13536,12 @@ static int perf_cgroup_css_online(struct cgroup_subsys_state *css)
 static int __perf_cgroup_move(void *info)
 {
 	struct task_struct *task = info;
-	rcu_read_lock();
-	perf_cgroup_switch(task);
-	rcu_read_unlock();
+
+	preempt_disable();
+	if (atomic_read(this_cpu_ptr(&perf_cgroup_events)))
+		perf_cgroup_switch(task);
+	preempt_enable();
+
 	return 0;
 }