This revision was automatically updated to reflect the committed changes.
Closed by commit rG89a3691b794c: [lldb] Fix ThreadedCommunication races
(authored by labath).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D133410/new/
https://reviews.llvm.org/D133410
Files:
lldb/source/Core/ThreadedCommunication.cpp
Index: lldb/source/Core/ThreadedCommunication.cpp
===================================================================
--- lldb/source/Core/ThreadedCommunication.cpp
+++ lldb/source/Core/ThreadedCommunication.cpp
@@ -104,34 +104,50 @@
return 0;
}
+ // No data yet, we have to start listening.
ListenerSP listener_sp(
Listener::MakeListener("ThreadedCommunication::Read"));
listener_sp->StartListeningForEvents(
this, eBroadcastBitReadThreadGotBytes | eBroadcastBitReadThreadDidExit);
- EventSP event_sp;
- while (listener_sp->GetEvent(event_sp, timeout)) {
- const uint32_t event_type = event_sp->GetType();
- if (event_type & eBroadcastBitReadThreadGotBytes) {
- return GetCachedBytes(dst, dst_len);
- }
- if (event_type & eBroadcastBitReadThreadDidExit) {
- // If the thread exited of its own accord, it either means it
- // hit an end-of-file condition or an error.
- status = m_pass_status;
- if (error_ptr)
- *error_ptr = std::move(m_pass_error);
+ // Re-check for data, as it might have arrived while we were setting up our
+ // listener.
+ cached_bytes = GetCachedBytes(dst, dst_len);
+ if (cached_bytes > 0) {
+ status = eConnectionStatusSuccess;
+ return cached_bytes;
+ }
- if (GetCloseOnEOF())
- Disconnect(nullptr);
+ EventSP event_sp;
+ // Explicitly check for the thread exit, for the same reason.
+ if (m_read_thread_did_exit) {
+ // We've missed the event, lets just conjure one up.
+ event_sp = std::make_shared<Event>(eBroadcastBitReadThreadDidExit);
+ } else {
+ if (!listener_sp->GetEvent(event_sp, timeout)) {
+ if (error_ptr)
+ error_ptr->SetErrorString("Timed out.");
+ status = eConnectionStatusTimedOut;
return 0;
}
}
+ const uint32_t event_type = event_sp->GetType();
+ if (event_type & eBroadcastBitReadThreadGotBytes) {
+ return GetCachedBytes(dst, dst_len);
+ }
- if (error_ptr)
- error_ptr->SetErrorString("Timed out.");
- status = eConnectionStatusTimedOut;
- return 0;
+ if (event_type & eBroadcastBitReadThreadDidExit) {
+ // If the thread exited of its own accord, it either means it
+ // hit an end-of-file condition or an error.
+ status = m_pass_status;
+ if (error_ptr)
+ *error_ptr = std::move(m_pass_error);
+
+ if (GetCloseOnEOF())
+ Disconnect(nullptr);
+ return 0;
+ }
+ llvm_unreachable("Got unexpected event type!");
}
// We aren't using a read thread, just read the data synchronously in this
@@ -299,22 +315,25 @@
m_pass_error = std::move(error);
LLDB_LOG(log, "Communication({0}) thread exiting...", this);
- // Handle threads wishing to synchronize with us.
- {
- // Prevent new ones from showing up.
- m_read_thread_did_exit = true;
+ // Start shutting down. We need to do this in a very specific order to ensure
+ // we don't race with threads wanting to read/synchronize with us.
- // Unblock any existing thread waiting for the synchronization signal.
- BroadcastEvent(eBroadcastBitNoMorePendingInput);
+ // First, we signal our intent to exit. This ensures no new thread start
+ // waiting on events from us.
+ m_read_thread_did_exit = true;
- // Wait for the thread to finish...
+ // Unblock any existing thread waiting for the synchronization signal.
+ BroadcastEvent(eBroadcastBitNoMorePendingInput);
+
+ {
+ // Wait for the synchronization thread to finish...
std::lock_guard<std::mutex> guard(m_synchronize_mutex);
// ... and disconnect.
if (disconnect)
Disconnect();
}
- // Let clients know that this thread is exiting
+ // Finally, unblock any readers waiting for us to exit.
BroadcastEvent(eBroadcastBitReadThreadDidExit);
return {};
}
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