On Mon, Nov 20, 2023 at 03:54:14PM -0500, Mathieu Desnoyers wrote: > When invoked from system call enter/exit instrumentation, accessing > user-space data is a common use-case for tracers. However, tracepoints > currently disable preemption around iteration on the registered > tracepoint probes and invocation of the probe callbacks, which prevents > tracers from handling page faults. > > Extend the tracepoint and trace event APIs to allow defining a faultable > tracepoint which invokes its callback with preemption enabled. > > Also extend the tracepoint API to allow tracers to request specific > probes to be connected to those faultable tracepoints. When the > TRACEPOINT_MAY_FAULT flag is provided on registration, the probe > callback will be called with preemption enabled, and is allowed to take > page faults. Faultable probes can only be registered on faultable > tracepoints and non-faultable probes on non-faultable tracepoints. > > The tasks trace rcu mechanism is used to synchronize read-side > marshalling of the registered probes with respect to faultable probes > unregistration and teardown. What is trace-trace rcu and why is it needed here? What's wrong with SRCU ?
