fix(profiling): ensure correct order of profiler post-fork hooks

ddtrace/internal/datadog/profiling/stack/src/sampler.cpp

@@ -351,6 +351,15 @@ stack_init()
 {
     // At just do start-of-process cleanup (e.g., set PID)
     stack_postfork_cleanup();
+
+    // The fork handler is registered at library load time to make sure it
+    // is registered before dd_wrapper's.
+    // The rationale is that both stack and dd_wrapper have post-fork hooks;
+    // and stack needs dd_wrapper's hooks to have completed as it needs the
+    // Profile object to have been reset and be ready for use, and post-fork
+    // hooks are executed in LIFO order.
+    // More details in https://github.com/DataDog/dd-trace-py/pull/17183
+    pthread_atfork(nullptr, nullptr, stack_atfork_child);
 }
 
 void
@@ -359,7 +368,6 @@ Sampler::one_time_setup()
     // It is unlikely, but possible, that the caller has forked since application startup, but before starting echion.
     // Run the cleanup to ensure that we're tracking the correct process.
     stack_postfork_cleanup();
-    pthread_atfork(nullptr, nullptr, stack_atfork_child);
 }
 
 void

releasenotes/notes/fix-profiler-postfork-hook-ordering.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    profiling: A rare crash that could occur post-fork in fork-based applications has been fixed.