Teach StartupAnalyzer to handle threads with no slices

Sometimes we end up with threads that have no slices to them, which was crashing
the startup analyzer. This change uses POSITIVE_INFINITY as the start time for
threads with no slices.

This change also includes a regression test that was generated by reducing a
trace that exercised this bug. Further regression tests should now be easier to
add.

Test: atest
Change-Id: Ibc82abb6406689b2e1f8c15558458d16e9f3f65d

4 files changed, 90 insertions, 1 deletions

diff --git a/Android.bp b/Android.bp
index c5dcc62..7fd8807 100644
--- a/Android.bp
+++ b/Android.bp
@@ -61,6 +61,22 @@ java_test_host {
     test_suites: ["general-tests"],
 }
 
+java_test_host {
+    name: "trebuchet-startup-common-tests",
+    defaults: ["trebuchet-defaults"],
+    srcs: [
+        "trebuchet/startup-common/test/**/*.kt",
+    ],
+    static_libs: [
+        "trebuchet-core",
+        "trebuchet-startup-common",
+    ],
+    libs: [
+        "junit",
+    ],
+    test_suites: ["general-tests"],
+}
+
 java_binary_host {
     name: "AnalyzerKt",
     defaults: ["trebuchet-defaults"],
diff --git a/TEST_MAPPING b/TEST_MAPPING
index 97a5fde..5be5baf 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -8,6 +8,10 @@
           "exclude-annotation": "trebuchet.testutils.NeedsSampleData"
         }
       ]
+    },
+    {
+      "name": "trebuchet-startup-common-tests",
+      "host": true
     }
   ]
 }
diff --git a/trebuchet/startup-common/src/StartupCommon.kt b/trebuchet/startup-common/src/StartupCommon.kt
index da6c378..13345c5 100644
--- a/trebuchet/startup-common/src/StartupCommon.kt
+++ b/trebuchet/startup-common/src/StartupCommon.kt
@@ -210,7 +210,7 @@ fun Model.getStartupEvents() : List<StartupEvent> {
             val newProc        = this.findProcess(newProcName, systemServerSlice.startTime, systemServerSlice.endTime)
             val startProcSlice = systemServerProc.findFirstSlice(SLICE_NAME_PROC_START, newProcName, systemServerSlice.startTime, systemServerSlice.endTime)
             val rfdSlice       = systemServerProc.findFirstSliceOrNull(SLICE_NAME_REPORT_FULLY_DRAWN, newProcName, systemServerSlice.startTime)
-            val firstSliceTime = newProc.threads.map { it.slices.first().startTime }.min()!!
+            val firstSliceTime = newProc.threads.map { it.slices.firstOrNull()?.startTime ?: Double.POSITIVE_INFINITY }.min()!!
 
             val schedSliceInfo : MutableMap<SchedulingState, Double> = mutableMapOf()
             newProc.threads.first().schedSlices.forEach schedLoop@ { schedSlice ->
diff --git a/trebuchet/startup-common/test/StartupCommonTests.kt b/trebuchet/startup-common/test/StartupCommonTests.kt
new file mode 100644
index 0000000..0a73d70
--- /dev/null
+++ b/trebuchet/startup-common/test/StartupCommonTests.kt
@@ -0,0 +1,69 @@
+/*
+ * Copyright 2019 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package trebuchet.analyzer.startup
+
+import getStartupEvents
+import org.junit.Test
+import trebuchet.io.BufferProducer
+import trebuchet.io.DataSlice
+import trebuchet.io.asSlice
+import trebuchet.model.Model
+import trebuchet.task.ImportTask
+import trebuchet.util.PrintlnImportFeedback
+
+fun parseString(source: String): Model {
+    val task = ImportTask(PrintlnImportFeedback())
+    return task.import(object : BufferProducer {
+        var hasRead = false
+        override fun next(): DataSlice? {
+            if (hasRead) return null
+            hasRead = true
+            return source.asSlice()
+        }
+    })
+}
+
+class StartupCommonTest {
+    @Test
+    fun testEmptyThreadStart() {
+        // This is a reduced trace based on one seen in the wild that used to
+        // crash because it creates a thread with no slices assigned to it.
+        val test = """
+TRACE:
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 289801/289801   #P:4
+#
+#                                      _-----=> irqs-off
+#                                     / _----=> need-resched
+#                                    | / _---=> hardirq/softirq
+#                                    || / _--=> preempt-depth
+#                                    ||| /     delay
+#           TASK-PID    TGID   CPU#  ||||    TIMESTAMP  FUNCTION
+#              | |        |      |   ||||       |         |
+   Binder:980_13-3951  (  980) [002] ...1  1628.269667: tracing_mark_write: E|980
+   Binder:980_13-3951  (  980) [002] ...2  1628.270068: tracing_mark_write: S|980|launching: com.example.eholk.myfirstapp|0
+           <...>-1104  (-----) [000] ...1  1628.292040: tracing_mark_write: B|980|Start proc: com.example.eholk.myfirstapp
+           <...>-1103  (-----) [002] d..4  1628.300748: sched_waking: comm=system_server pid=980 prio=118 target_cpu=001
+    RenderThread-9817  ( 9793) [003] d..3  1628.457017: sched_waking: comm=holk.myfirstapp pid=9793 prio=110 target_cpu=002
+    RenderThread-9817  ( 9793) [003] ...1  1628.457191: tracing_mark_write: B|9793|Thread birth
+        """
+
+        val trace = parseString(test)
+        trace.getStartupEvents()
+    }
+}