1 files changed, 80 insertions, 0 deletions
diff --git a/packages/Python/lldbsuite/test/functionalities/expr-doesnt-deadlock/locking.c b/packages/Python/lldbsuite/test/functionalities/expr-doesnt-deadlock/locking.c
new file mode 100644
index 0000000..fae9979
--- /dev/null
+++ b/packages/Python/lldbsuite/test/functionalities/expr-doesnt-deadlock/locking.c
@@ -0,0 +1,80 @@
+#include <pthread.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+
+pthread_mutex_t contended_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+pthread_mutex_t control_mutex = PTHREAD_MUTEX_INITIALIZER;
+pthread_cond_t  control_condition;
+
+pthread_mutex_t thread_started_mutex = PTHREAD_MUTEX_INITIALIZER;
+pthread_cond_t  thread_started_condition;
+
+// This function runs in a thread.  The locking dance is to make sure that 
+// by the time the main thread reaches the pthread_join below, this thread
+// has for sure acquired the contended_mutex.  So then the call_me_to_get_lock
+// function will block trying to get the mutex, and only succeed once it
+// signals this thread, then lets it run to wake up from the cond_wait and
+// release the mutex.
+
+void *
+lock_acquirer_1 (void *input)
+{
+  pthread_mutex_lock (&contended_mutex);
+  
+  // Grab this mutex, that will ensure that the main thread
+  // is in its cond_wait for it (since that's when it drops the mutex.
+
+  pthread_mutex_lock (&thread_started_mutex);
+  pthread_mutex_unlock(&thread_started_mutex);
+
+  // Now signal the main thread that it can continue, we have the contended lock
+  // so the call to call_me_to_get_lock won't make any progress till  this
+  // thread gets a chance to run.
+
+  pthread_mutex_lock (&control_mutex);
+
+  pthread_cond_signal (&thread_started_condition);
+
+  pthread_cond_wait (&control_condition, &control_mutex);
+
+  pthread_mutex_unlock (&contended_mutex);
+  return NULL;
+}
+
+int
+call_me_to_get_lock ()
+{
+  pthread_cond_signal (&control_condition);
+  pthread_mutex_lock (&contended_mutex);
+  return 567;
+}
+
+int main ()
+{
+  pthread_t thread_1;
+
+  pthread_cond_init (&control_condition, NULL);
+  pthread_cond_init (&thread_started_condition, NULL);
+
+  pthread_mutex_lock (&thread_started_mutex);
+
+  pthread_create (&thread_1, NULL, lock_acquirer_1, NULL);
+  
+  pthread_cond_wait (&thread_started_condition, &thread_started_mutex);
+
+  pthread_mutex_lock (&control_mutex);
+  pthread_mutex_unlock (&control_mutex);
+
+  // Break here.  At this point the other thread will have the contended_mutex,
+  // and be sitting in its cond_wait for the control condition.  So there is
+  // no way that our by-hand calling of call_me_to_get_lock will proceed
+  // without running the first thread at least somewhat.
+
+  call_me_to_get_lock();
+  pthread_join (thread_1, NULL);
+
+  return 0;
+
+}