bug 1686726 - Fix lock order inversion in RLB Timing Distribution

mozilla · Jan 14, 2021 · 98520aa · 98520aa
1 parent 8ae896f
commit 98520aa
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -4,6 +4,8 @@
 
 * Android
   * A new metric `glean.validation.foreground_count` was added to the metrics ping.
+* Rust
+  * BUGFIX: Fix lock order inversion in RLB Timing Distribution ([#1431](https://github.com/mozilla/glean/pull/1431)).
 
 # v33.10.1 (2021-01-06)
 

diff --git a/glean-core/rlb/src/private/timing_distribution.rs b/glean-core/rlb/src/private/timing_distribution.rs
@@ -65,12 +65,18 @@ impl glean_core::traits::TimingDistribution for TimingDistributionMetric {
     ) -> Option<DistributionData> {
         crate::block_on_dispatcher();
 
-        let inner = self.0.read().unwrap();
-        let queried_ping_name = ping_name
-            .into()
-            .unwrap_or_else(|| &inner.meta().send_in_pings[0]);
+        crate::with_glean(|glean| {
+            // The order of taking these locks matter. Glean must be first.
+            let inner = self
+                .0
+                .read()
+                .expect("Lock poisoned for timing distribution metric on test_get_value.");
+            let queried_ping_name = ping_name
+                .into()
+                .unwrap_or_else(|| &inner.meta().send_in_pings[0]);
 
-        crate::with_glean(|glean| inner.test_get_value(glean, queried_ping_name))
+            inner.test_get_value(glean, queried_ping_name)
+        })
     }
 
     fn test_get_num_recorded_errors<'a, S: Into<Option<&'a str>>>(