Introduce new command: thread backtrace unique

This patch introduces a new thread backtrace command "unique".
The command is based off of "thread backtrace all" but will instead
find all threads which share matching call stacks and de-duplicate
their output, listing call stack and all the threads which share it.
This is especially useful for apps which use thread/task pools
sitting around waiting for work and cause excessive duplicate output.
I needed this behavior recently when debugging a core with 700+ threads.

Differential Revision: https://reviews.llvm.org/D33426

Reviewers: clayborg, jingham
Patch by Brian Gianforcaro <b.gianfo@gmail.com>

llvm-svn: 305197

lldb/include/lldb/Core/Debugger.h

@@ -249,6 +249,8 @@ class Debugger : public std::enable_shared_from_this<Debugger>,
 
   const FormatEntity::Entry *GetFrameFormat() const;
 
+  const FormatEntity::Entry *GetFrameFormatUnique() const;
+
   const FormatEntity::Entry *GetThreadFormat() const;
 
   const FormatEntity::Entry *GetThreadStopFormat() const;

lldb/include/lldb/Target/StackFrame.h

@@ -342,10 +342,13 @@ class StackFrame : public ExecutionContextScope,
   /// @param [in] strm
   ///   The Stream to print the description to.
   ///
+  /// @param [in] show_unique
+  ///   Whether to print the function arguments or not for backtrace unique.
+  ///
   /// @param [in] frame_marker
   ///   Optional string that will be prepended to the frame output description.
   //------------------------------------------------------------------
-  void DumpUsingSettingsFormat(Stream *strm,
+  void DumpUsingSettingsFormat(Stream *strm, bool show_unique = false,
                                const char *frame_marker = nullptr);
 
   //------------------------------------------------------------------
@@ -375,14 +378,18 @@ class StackFrame : public ExecutionContextScope,
   /// @param[in] show_source
   ///   If true, print source or disassembly as per the user's settings.
   ///
+  /// @param[in] show_unique
+  ///   If true, print using backtrace unique style, without function
+  ///            arguments as per the user's settings.
+  ///
   /// @param[in] frame_marker
   ///   Passed to DumpUsingSettingsFormat() for the frame info printing.
   ///
   /// @return
   ///   Returns true if successful.
   //------------------------------------------------------------------
   bool GetStatus(Stream &strm, bool show_frame_info, bool show_source,
-                 const char *frame_marker = nullptr);
+                 bool show_unique = false, const char *frame_marker = nullptr);
 
   //------------------------------------------------------------------
   /// Query whether this frame is a concrete frame on the call stack,

lldb/include/lldb/Target/StackFrameList.h

@@ -70,6 +70,7 @@ class StackFrameList {
 
   size_t GetStatus(Stream &strm, uint32_t first_frame, uint32_t num_frames,
                    bool show_frame_info, uint32_t num_frames_with_source,
+                   bool show_unique = false,
                    const char *frame_marker = nullptr);
 
 protected:

lldb/include/lldb/Target/Thread.h

@@ -1163,8 +1163,8 @@ class Thread : public std::enable_shared_from_this<Thread>,
   GetStackFrameSPForStackFramePtr(StackFrame *stack_frame_ptr);
 
   size_t GetStatus(Stream &strm, uint32_t start_frame, uint32_t num_frames,
-                   uint32_t num_frames_with_source,
-                   bool stop_format);
+                   uint32_t num_frames_with_source, bool stop_format,
+                   bool only_stacks = false);
 
   size_t GetStackFrameStatus(Stream &strm, uint32_t first_frame,
                              uint32_t num_frames, bool show_frame_info,

lldb/packages/Python/lldbsuite/test/functionalities/thread/num_threads/TestNumThreads.py

@@ -19,26 +19,27 @@ class NumberOfThreadsTestCase(TestBase):
     def setUp(self):
         # Call super's setUp().
         TestBase.setUp(self)
-        # Find the line number to break inside main().
-        self.line = line_number('main.cpp', '// Set break point at this line.')
+        # Find the line numbers for our break points.
+        self.thread3_notify_all_line = line_number('main.cpp', '// Set thread3 break point on notify_all at this line.')
+        self.thread3_before_lock_line = line_number('main.cpp', '// Set thread3 break point on lock at this line.')
 
-    def test(self):
+    def test_number_of_threads(self):
         """Test number of threads."""
         self.build()
         exe = os.path.join(os.getcwd(), "a.out")
         self.runCmd("file " + exe, CURRENT_EXECUTABLE_SET)
 
         # This should create a breakpoint with 1 location.
         lldbutil.run_break_set_by_file_and_line(
-            self, "main.cpp", self.line, num_expected_locations=1)
+            self, "main.cpp", self.thread3_notify_all_line, num_expected_locations=1)
 
-        # The breakpoint list should show 3 locations.
+        # The breakpoint list should show 1 location.
         self.expect(
             "breakpoint list -f",
             "Breakpoint location shown correctly",
             substrs=[
                 "1: file = 'main.cpp', line = %d, exact_match = 0, locations = 1" %
-                self.line])
+                self.thread3_notify_all_line])
 
         # Run the program.
         self.runCmd("run", RUN_SUCCEEDED)
@@ -57,5 +58,64 @@ def test(self):
         # Using std::thread may involve extra threads, so we assert that there are
         # at least 4 rather than exactly 4.
         self.assertTrue(
-            num_threads >= 4,
+            num_threads >= 13,
             'Number of expected threads and actual threads do not match.')
+
+    def test_unique_stacks(self):
+        """Test backtrace unique with multiple threads executing the same stack."""
+        self.build()
+        exe = os.path.join(os.getcwd(), "a.out")
+        self.runCmd("file " + exe, CURRENT_EXECUTABLE_SET)
+
+        # Set a break point on the thread3 notify all (should get hit on threads 4-13).
+        lldbutil.run_break_set_by_file_and_line(
+            self, "main.cpp", self.thread3_before_lock_line, num_expected_locations=1)
+
+        # Run the program.
+        self.runCmd("run", RUN_SUCCEEDED)
+
+        # Stopped once.
+        self.expect("thread list", STOPPED_DUE_TO_BREAKPOINT,
+                    substrs=["stop reason = breakpoint 1."])
+
+        process = self.process()
+
+        # Get the number of threads
+        num_threads = process.GetNumThreads()
+
+        # Using std::thread may involve extra threads, so we assert that there are
+        # at least 10 thread3's rather than exactly 10.
+        self.assertTrue(
+            num_threads >= 10,
+            'Number of expected threads and actual threads do not match.')
+
+        # Attempt to walk each of the thread's executing the thread3 function to
+        # the same breakpoint.
+        def is_thread3(thread):
+            for frame in thread:
+                if "thread3" in frame.GetFunctionName(): return True
+            return False
+
+        expect_threads = ""
+        for i in range(num_threads):
+            thread = process.GetThreadAtIndex(i)
+            self.assertTrue(thread.IsValid())
+            if not is_thread3(thread):
+                continue
+
+            # If we aren't stopped out the thread breakpoint try to resume.
+            if thread.GetStopReason() != lldb.eStopReasonBreakpoint:
+                self.runCmd("thread continue %d"%(i+1))
+            self.assertEqual(thread.GetStopReason(), lldb.eStopReasonBreakpoint)
+
+            expect_threads += " #%d"%(i+1)
+
+        # Construct our expected back trace string
+        expect_string = "10 thread(s)%s" % (expect_threads)
+
+        # Now that we are stopped, we should have 10 threads waiting in the
+        # thread3 function. All of these threads should show as one stack.
+        self.expect("thread backtrace unique",
+                    "Backtrace with unique stack shown correctly",
+                    substrs=[expect_string,
+                        "main.cpp:%d"%self.thread3_before_lock_line])

lldb/packages/Python/lldbsuite/test/functionalities/thread/num_threads/main.cpp

@@ -1,23 +1,27 @@
+#include "pseudo_barrier.h"
 #include <condition_variable>
 #include <mutex>
 #include <thread>
+#include <vector>
 
 std::mutex mutex;
 std::condition_variable cond;
+pseudo_barrier_t thread3_barrier;
 
 void *
 thread3(void *input)
 {
-    std::unique_lock<std::mutex> lock(mutex);
-    cond.notify_all(); // Set break point at this line.
+    pseudo_barrier_wait(thread3_barrier);
+    std::unique_lock<std::mutex> lock(mutex); // Set thread3 break point on lock at this line.
+    cond.notify_all(); // Set thread3 break point on notify_all at this line.
     return NULL;
 }
 
 void *
 thread2(void *input)
 {
     std::unique_lock<std::mutex> lock(mutex);
-    cond.notify_all();
+    cond.notify_all(); // release main thread
     cond.wait(lock);
     return NULL;
 }
@@ -36,15 +40,23 @@ int main()
     std::unique_lock<std::mutex> lock(mutex);
 
     std::thread thread_1(thread1, nullptr);
-    cond.wait(lock);
+    cond.wait(lock); // wait for thread2
 
-    std::thread thread_3(thread3, nullptr);
-    cond.wait(lock);
+    pseudo_barrier_init(thread3_barrier, 10);
+
+    std::vector<std::thread> thread_3s;
+    for (int i = 0; i < 10; i++) {
+      thread_3s.push_back(std::thread(thread3, nullptr));
+    }
+
+    cond.wait(lock); // wait for thread_3s
 
     lock.unlock();
 
     thread_1.join();
-    thread_3.join();
+    for (auto &t : thread_3s){
+        t.join();
+    }
 
     return 0;
 }