Avoid use of pthread_getschedparam

During Thread::DumpState the pthread may have exited.
We have the tid, use that instead.

Test: m -j50 test-art-host -k
Test: adb shell kill -3 `pid system_server`
Bug: 36445592
Change-Id: Idb28fcb1f9232768d32966973fe9dbeb3fa74b56
diff --git a/runtime/thread.cc b/runtime/thread.cc
index 30a4046..ee77945 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -17,6 +17,7 @@
 #include "thread.h"
 
 #include <pthread.h>
+#include <sched.h>
 #include <signal.h>
 #include <sys/resource.h>
 #include <sys/time.h>
@@ -1589,10 +1590,17 @@
      << " nice=" << getpriority(PRIO_PROCESS, tid)
      << " cgrp=" << scheduler_group_name;
   if (thread != nullptr) {
-    int policy;
+    // b/36445592 Don't use pthread_getschedparam since pthread may have exited.
+    int policy = sched_getscheduler(tid);
+    if (policy == -1) {
+      PLOG(WARNING) << "sched_getscheduler(" << tid << ")";
+    }
     sched_param sp;
-    CHECK_PTHREAD_CALL(pthread_getschedparam, (thread->tlsPtr_.pthread_self, &policy, &sp),
-                       __FUNCTION__);
+    int sched_getparam_result = sched_getparam(tid, &sp);
+    if (sched_getparam_result == -1) {
+      PLOG(WARNING) << "sched_getparam(" << tid << ", &sp)";
+      sp.sched_priority = -1;
+    }
     os << " sched=" << policy << "/" << sp.sched_priority
        << " handle=" << reinterpret_cast<void*>(thread->tlsPtr_.pthread_self);
   }