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
diff --git a/lldb/source/Commands/CommandObjectThread.cpp b/lldb/source/Commands/CommandObjectThread.cpp
index b585ef9..cfd8fcb 100644
--- a/lldb/source/Commands/CommandObjectThread.cpp
+++ b/lldb/source/Commands/CommandObjectThread.cpp
@@ -42,10 +42,44 @@
using namespace lldb_private;
//-------------------------------------------------------------------------
-// CommandObjectThreadBacktrace
+// CommandObjectIterateOverThreads
//-------------------------------------------------------------------------
class CommandObjectIterateOverThreads : public CommandObjectParsed {
+
+ class UniqueStack {
+
+ public:
+ UniqueStack(std::stack<lldb::addr_t> stack_frames, uint32_t thread_index_id)
+ : m_stack_frames(stack_frames) {
+ m_thread_index_ids.push_back(thread_index_id);
+ }
+
+ void AddThread(uint32_t thread_index_id) const {
+ m_thread_index_ids.push_back(thread_index_id);
+ }
+
+ const std::vector<uint32_t> &GetUniqueThreadIndexIDs() const {
+ return m_thread_index_ids;
+ }
+
+ lldb::tid_t GetRepresentativeThread() const {
+ return m_thread_index_ids.front();
+ }
+
+ friend bool inline operator<(const UniqueStack &lhs,
+ const UniqueStack &rhs) {
+ return lhs.m_stack_frames < rhs.m_stack_frames;
+ }
+
+ protected:
+ // Mark the thread index as mutable, as we don't care about it from a const
+ // perspective, we only care about m_stack_frames so we keep our std::set
+ // sorted.
+ mutable std::vector<uint32_t> m_thread_index_ids;
+ std::stack<lldb::addr_t> m_stack_frames;
+ };
+
public:
CommandObjectIterateOverThreads(CommandInterpreter &interpreter,
const char *name, const char *help,
@@ -57,11 +91,15 @@
bool DoExecute(Args &command, CommandReturnObject &result) override {
result.SetStatus(m_success_return);
+ bool all_threads = false;
if (command.GetArgumentCount() == 0) {
Thread *thread = m_exe_ctx.GetThreadPtr();
if (!HandleOneThread(thread->GetID(), result))
return false;
return result.Succeeded();
+ } else if (command.GetArgumentCount() == 1) {
+ all_threads = ::strcmp(command.GetArgumentAtIndex(0), "all") == 0;
+ m_unique_stacks = ::strcmp(command.GetArgumentAtIndex(0), "unique") == 0;
}
// Use tids instead of ThreadSPs to prevent deadlocking problems which
@@ -69,8 +107,7 @@
// code while iterating over the (locked) ThreadSP list.
std::vector<lldb::tid_t> tids;
- if (command.GetArgumentCount() == 1 &&
- ::strcmp(command.GetArgumentAtIndex(0), "all") == 0) {
+ if (all_threads || m_unique_stacks) {
Process *process = m_exe_ctx.GetProcessPtr();
for (ThreadSP thread_sp : process->Threads())
@@ -108,15 +145,47 @@
}
}
- uint32_t idx = 0;
- for (const lldb::tid_t &tid : tids) {
- if (idx != 0 && m_add_return)
- result.AppendMessage("");
+ if (m_unique_stacks) {
+ // Iterate over threads, finding unique stack buckets.
+ std::set<UniqueStack> unique_stacks;
+ for (const lldb::tid_t &tid : tids) {
+ if (!BucketThread(tid, unique_stacks, result)) {
+ return false;
+ }
+ }
- if (!HandleOneThread(tid, result))
- return false;
+ // Write the thread id's and unique call stacks to the output stream
+ Stream &strm = result.GetOutputStream();
+ Process *process = m_exe_ctx.GetProcessPtr();
+ for (const UniqueStack &stack : unique_stacks) {
+ // List the common thread ID's
+ const std::vector<uint32_t> &thread_index_ids =
+ stack.GetUniqueThreadIndexIDs();
+ strm.Printf("%lu thread(s) ", thread_index_ids.size());
+ for (const uint32_t &thread_index_id : thread_index_ids) {
+ strm.Printf("#%u ", thread_index_id);
+ }
+ strm.EOL();
- ++idx;
+ // List the shared call stack for this set of threads
+ uint32_t representative_thread_id = stack.GetRepresentativeThread();
+ ThreadSP thread = process->GetThreadList().FindThreadByIndexID(
+ representative_thread_id);
+ if (!HandleOneThread(thread->GetID(), result)) {
+ return false;
+ }
+ }
+ } else {
+ uint32_t idx = 0;
+ for (const lldb::tid_t &tid : tids) {
+ if (idx != 0 && m_add_return)
+ result.AppendMessage("");
+
+ if (!HandleOneThread(tid, result))
+ return false;
+
+ ++idx;
+ }
}
return result.Succeeded();
}
@@ -134,7 +203,43 @@
virtual bool HandleOneThread(lldb::tid_t, CommandReturnObject &result) = 0;
+ bool BucketThread(lldb::tid_t tid, std::set<UniqueStack> &unique_stacks,
+ CommandReturnObject &result) {
+ // Grab the corresponding thread for the given thread id.
+ Process *process = m_exe_ctx.GetProcessPtr();
+ Thread *thread = process->GetThreadList().FindThreadByID(tid).get();
+ if (thread == nullptr) {
+ result.AppendErrorWithFormat("Failed to process thread# %lu.\n", tid);
+ result.SetStatus(eReturnStatusFailed);
+ return false;
+ }
+
+ // Collect the each frame's address for this call-stack
+ std::stack<lldb::addr_t> stack_frames;
+ const uint32_t frame_count = thread->GetStackFrameCount();
+ for (uint32_t frame_index = 0; frame_index < frame_count; frame_index++) {
+ const lldb::StackFrameSP frame_sp =
+ thread->GetStackFrameAtIndex(frame_index);
+ const lldb::addr_t pc = frame_sp->GetStackID().GetPC();
+ stack_frames.push(pc);
+ }
+
+ uint32_t thread_index_id = thread->GetIndexID();
+ UniqueStack new_unique_stack(stack_frames, thread_index_id);
+
+ // Try to match the threads stack to and existing entry.
+ std::set<UniqueStack>::iterator matching_stack =
+ unique_stacks.find(new_unique_stack);
+ if (matching_stack != unique_stacks.end()) {
+ matching_stack->AddThread(thread_index_id);
+ } else {
+ unique_stacks.insert(new_unique_stack);
+ }
+ return true;
+ }
+
ReturnStatus m_success_return = eReturnStatusSuccessFinishResult;
+ bool m_unique_stacks = false;
bool m_add_return = true;
};
@@ -218,9 +323,10 @@
: CommandObjectIterateOverThreads(
interpreter, "thread backtrace",
"Show thread call stacks. Defaults to the current thread, thread "
- "indexes can be specified as arguments. Use the thread-index "
- "\"all\" "
- "to see all threads.",
+ "indexes can be specified as arguments.\n"
+ "Use the thread-index \"all\" to see all threads.\n"
+ "Use the thread-index \"unique\" to see threads grouped by unique "
+ "call stacks.",
nullptr,
eCommandRequiresProcess | eCommandRequiresThread |
eCommandTryTargetAPILock | eCommandProcessMustBeLaunched |
@@ -270,11 +376,14 @@
Stream &strm = result.GetOutputStream();
+ // Only dump stack info if we processing unique stacks.
+ const bool only_stacks = m_unique_stacks;
+
// Don't show source context when doing backtraces.
const uint32_t num_frames_with_source = 0;
const bool stop_format = true;
if (!thread->GetStatus(strm, m_options.m_start, m_options.m_count,
- num_frames_with_source, stop_format)) {
+ num_frames_with_source, stop_format, only_stacks)) {
result.AppendErrorWithFormat(
"error displaying backtrace for thread: \"0x%4.4x\"\n",
thread->GetIndexID());