On Mon, Feb 14, 2022 at 10:29 AM Hao Luo <haoluo@xxxxxxxxxx> wrote: > Hi Alexei, > > Actually, I found this almost worked, except that the tracepoints > cgroup_mkdir and cgroup_rmdir are not sleepable. They are inside a > spinlock's critical section with irq off. I guess one solution is to > offload the sleepable part of the bpf prog into a thread context. We > may create a dedicated kernel thread or use workqueue for this. Do you > have any advice? Are you referring to spin_lock in TRACE_CGROUP_PATH that protects global trace_cgroup_path[] buffer? That is fixable. Do you actually need the string path returned by cgroup_path() in bpf prog? Maybe prog can call cgroup_path() by itself when necessary. Parsing strings isn't great anyway. The bpf prog probably needs the last part of the dir only. So cgrp->kn->name would do it? The TRACE_CGROUP_PATH wasn't designed to be turned on 24/7. That global spin_lock is not great for production use. No need to delegate sleepable bpf to thread context. Let's refactor that tracepoint a bit.
