Document limitation of vppid and ppid context wrt eventual RCU instrumentation

[lttng-modules.git] / lttng-context-vppid.c

diff --git a/lttng-context-vppid.c b/lttng-context-vppid.c
index 365d97394e89c98094b43dacc5918ee353271c00..06377a3098ff7f72b992f0c9848f693fbc10f7dc 100644 (file)
--- a/lttng-context-vppid.c
+++ b/lttng-context-vppid.c
@@ -51,6 +51,15 @@ void vppid_record(struct lttng_ctx_field *field,
         * current nsproxy can be NULL when scheduled out of exit. pid_vnr uses
         * the current thread nsproxy to perform the lookup.
         */
+
+       /*
+        * TODO: when we eventually add RCU subsystem instrumentation,
+        * taking the rcu read lock here will trigger RCU tracing
+        * recursively. We should modify the kernel synchronization so
+        * it synchronizes both for RCU and RCU sched, and rely on
+        * rcu_read_lock_sched_notrace.
+        */
+
        rcu_read_lock();
        parent = rcu_dereference(current->real_parent);
        if (!current->nsproxy)