Migrate tracepoint instrumentation to TP_FIELDS

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

diff --git a/lttng-context-vppid.c b/lttng-context-vppid.c
index c18c553148d6e41a0339b9f77faf0dbe0fd5c6f9..9f36375db08f449d840742b831cfb04b25a213e4 100644 (file)
--- a/lttng-context-vppid.c
+++ b/lttng-context-vppid.c
@@ -71,6 +71,36 @@ void vppid_record(struct lttng_ctx_field *field,
        chan->ops->event_write(ctx, &vppid, sizeof(vppid));
 }
 
+static
+void vppid_get_value(struct lttng_ctx_field *field,
+               union lttng_ctx_value *value)
+{
+       struct task_struct *parent;
+       pid_t vppid;
+
+       /*
+        * 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)
+               vppid = 0;
+       else
+               vppid = task_tgid_vnr(parent);
+       rcu_read_unlock();
+       value->s64 = vppid;
+}
+
 int lttng_add_vppid_to_ctx(struct lttng_ctx **ctx)
 {
        struct lttng_ctx_field *field;
@@ -92,6 +122,7 @@ int lttng_add_vppid_to_ctx(struct lttng_ctx **ctx)
        field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
        field->get_size = vppid_get_size;
        field->record = vppid_record;
+       field->get_value = vppid_get_value;
        lttng_context_update(*ctx);
        wrapper_vmalloc_sync_all();
        return 0;