perfetto_hprof: Unsuspend parent process before waitpid.

We have hit bugs where the child process got stuck in an atfork handler.
This way worst case the perfetto_hprof_listener thread gets stuck if the
child process does, but the rest of the app can go on normally.
The next step will be to add a timeout to the waitpid to make sure we
do not leak the child process.

Bug: 181031512
Test: atest CtsPerfettoTestCases
Change-Id: I9525c0fc5d061307b01dbacf2ec05f19b930ea25

1 files changed, 8 insertions, 3 deletions

diff --git a/perfetto_hprof/perfetto_hprof.cc b/perfetto_hprof/perfetto_hprof.cc
index ebba1e3e17..8bcf0bd125 100644
--- a/perfetto_hprof/perfetto_hprof.cc
+++ b/perfetto_hprof/perfetto_hprof.cc
@@ -32,6 +32,7 @@
 #include <time.h>
 
 #include <limits>
+#include <optional>
 #include <type_traits>
 
 #include "gc/heap-visit-objects-inl.h"
@@ -584,10 +585,10 @@ void DumpPerfetto(art::Thread* self) {
   // We need to do this before the fork, because otherwise it can deadlock
   // waiting for the GC, as all other threads get terminated by the clone, but
   // their locks are not released.
-  art::gc::ScopedGCCriticalSection gcs(self, art::gc::kGcCauseHprof,
-                                       art::gc::kCollectorTypeHprof);
+  std::optional<art::gc::ScopedGCCriticalSection> gcs(std::in_place, self, art::gc::kGcCauseHprof,
+                                                      art::gc::kCollectorTypeHprof);
 
-  art::ScopedSuspendAll ssa(__FUNCTION__, /* long_suspend=*/ true);
+  std::optional<art::ScopedSuspendAll> ssa(std::in_place, __FUNCTION__, /* long_suspend=*/ true);
 
   pid_t pid = fork();
   if (pid == -1) {
@@ -597,6 +598,10 @@ void DumpPerfetto(art::Thread* self) {
   }
   if (pid != 0) {
     // Parent
+    // Stop the thread suspension as soon as possible to allow the rest of the application to
+    // continue while we waitpid here.
+    ssa.reset();
+    gcs.reset();
     int stat_loc;
     for (;;) {
       if (waitpid(pid, &stat_loc, 0) != -1 || errno != EINTR) {