exit optional, close cleans up stored stacks

stacks/src/bpf.rs

@@ -6,7 +6,7 @@ use libbpf_rs::{
     skel::{OpenSkel, SkelBuilder},
     Link,
 };
-use tracing::warn;
+use tracing::info;
 
 use crate::{
     perf_event::{attach_perf_event, perf_event_per_cpu},
@@ -629,20 +629,20 @@ pub(crate) fn link<'a>(
             .progs_mut()
             .stacks_tracing_exit()
             .attach_usdt(-1, u, "stacks_tracing", "exit")
-            .context("usdt exit")?;
-        let _usdt_close = skel
-            .progs_mut()
-            .stacks_tracing_close()
-            .attach_usdt(-1, u, "stacks_tracing", "close")
-            .context("usdt close");
-        match _usdt_close {
+            .context("usdt exit");
+        match _usdt_exit {
             Ok(link) => links.push(link),
             Err(err) => {
-                warn!("failed to attach usdt close to binary {:?}: {}", u, err);
+                info!("usdt exit is not attached to binary {:?}: {}", u, err);
             }
         }
+        let _usdt_close = skel
+            .progs_mut()
+            .stacks_tracing_close()
+            .attach_usdt(-1, u, "stacks_tracing", "close")
+            .context("usdt close")?;
         links.push(_usdt_enter);
-        links.push(_usdt_exit);
+        links.push(_usdt_close);
     }
 
     Ok((skel, links))

stacks/src/state.rs

@@ -271,20 +271,22 @@ impl<Fr: Frames, Sym: Symbolizer> State<Fr, Sym> {
                 });
             }
             Received::TraceClose(event) => {
-                // record it only once for any pid where this span_id has entered before
+                // record close event only once for any pid where this span_id has entered before
                 let pids = self
                     .tgid_span_id_pid_to_enter
                     .range((event.tgid, event.span_id, 0)..(event.tgid, event.span_id, u32::MAX))
                     .map(|(k, _)| k.2)
                     .collect::<Vec<_>>();
-                let process_info = self.tgid_process_info.get(&pids[0]);
+                let process_info = self.tgid_process_info.get(&event.tgid);
                 for (i, pid) in pids.into_iter().enumerate() {
+                    // delete all observed
                     let span = match self.tgid_span_id_pid_to_enter.remove(&(event.tgid, event.span_id, pid)) {
                         Some(span) => span,
                         None => {
                             anyhow::bail!("missing span for pid {} span_id {}", pid, event.span_id);
                         }
                     };
+                    // record only first
                     if i > 0 {
                         continue;
                     }