On Thu, Feb 18, 2021 at 01:24:16PM -0500, Steven Rostedt wrote: > On Thu, 18 Feb 2021 09:00:12 -0800 > "Paul E. McKenney" <paulmck@xxxxxxxxxx> wrote: > > > OK, I will bite. ;-) > > Do I turn into a wearwolf? Maybe even a wash-n-wear wolf. ;-) > > Can the saving of console into trace buffers be easily enabled and > > disabled within the code? > > Well, we do have this for ftrace: > > echo 'enable_event:printk:console' > events/rcu/rcu_stall_warning/trigger > > Would enable the printk console to be traced to the ring buffer once the > stall is triggered, and not before hand. > > > If so, does enabling and disabling nest? > > It has a disable as well, but unfortunately its global and does not nest. > We could always implement a percpu trigger that can nest though. So Sangmoon could have a module react to an RCU CPU stall warning tracepoint by turning on tracing of console messages. If there was a start-stop pair of RCU CPU stall warning tracepoints, he could turn it off as well. Not sure if that is what Sangmoon is looking for, but it is a possibility. Thanx, Paul
