Author: labath Date: Thu Oct 19 10:40:51 2017 New Revision: 316173 URL: http://llvm.org/viewvc/llvm-project?rev=316173&view=rev Log: Logging: Make sure logging machinery is in a consistent state after forking
Summary: We had a bug where if we had forked (in the ProcessLauncherPosixFork) while another thread was writing a log message, we would deadlock. This happened because the fork child inherited the locked log rwmutex, which would never get unlocked. This meant the child got stuck trying to disable all log channels. The bug existed for a while but only started being apparent after D37930, which started using ThreadLauncher (which uses logging) instead of std::thread (which does not) for launching TaskPool threads. The fix is to use pthread_atfork to make sure noone is writing a log message while we are forking. Reviewers: zturner, eugene, clayborg Subscribers: lldb-commits Differential Revision: https://reviews.llvm.org/D38938 Modified: lldb/trunk/include/lldb/Utility/Log.h lldb/trunk/include/lldb/Utility/Logging.h lldb/trunk/source/Initialization/SystemInitializerCommon.cpp lldb/trunk/source/Utility/Log.cpp lldb/trunk/source/Utility/Logging.cpp Modified: lldb/trunk/include/lldb/Utility/Log.h URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/include/lldb/Utility/Log.h?rev=316173&r1=316172&r2=316173&view=diff ============================================================================== --- lldb/trunk/include/lldb/Utility/Log.h (original) +++ lldb/trunk/include/lldb/Utility/Log.h Thu Oct 19 10:40:51 2017 @@ -96,6 +96,9 @@ public: } }; + + static void Initialize(); + //------------------------------------------------------------------ // Static accessors for logging channels //------------------------------------------------------------------ @@ -193,6 +196,9 @@ private: static uint32_t GetFlags(llvm::raw_ostream &stream, const ChannelMap::value_type &entry, llvm::ArrayRef<const char *> categories); + static void LockAllChannels(); + static void UnlockAllChannels(); + Log(const Log &) = delete; void operator=(const Log &) = delete; }; Modified: lldb/trunk/include/lldb/Utility/Logging.h URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/include/lldb/Utility/Logging.h?rev=316173&r1=316172&r2=316173&view=diff ============================================================================== --- lldb/trunk/include/lldb/Utility/Logging.h (original) +++ lldb/trunk/include/lldb/Utility/Logging.h Thu Oct 19 10:40:51 2017 @@ -62,7 +62,7 @@ Log *GetLogIfAllCategoriesSet(uint32_t m Log *GetLogIfAnyCategoriesSet(uint32_t mask); -void InitializeLog(); +void InitializeLldbChannel(); } // namespace lldb_private Modified: lldb/trunk/source/Initialization/SystemInitializerCommon.cpp URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Initialization/SystemInitializerCommon.cpp?rev=316173&r1=316172&r2=316173&view=diff ============================================================================== --- lldb/trunk/source/Initialization/SystemInitializerCommon.cpp (original) +++ lldb/trunk/source/Initialization/SystemInitializerCommon.cpp Thu Oct 19 10:40:51 2017 @@ -70,7 +70,7 @@ void SystemInitializerCommon::Initialize #endif llvm::EnablePrettyStackTrace(); - InitializeLog(); + Log::Initialize(); HostInfo::Initialize(); static Timer::Category func_cat(LLVM_PRETTY_FUNCTION); Timer scoped_timer(func_cat, LLVM_PRETTY_FUNCTION); Modified: lldb/trunk/source/Utility/Log.cpp URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Utility/Log.cpp?rev=316173&r1=316172&r2=316173&view=diff ============================================================================== --- lldb/trunk/source/Utility/Log.cpp (original) +++ lldb/trunk/source/Utility/Log.cpp Thu Oct 19 10:40:51 2017 @@ -32,6 +32,7 @@ #include <process.h> // for getpid #else #include <unistd.h> +#include <pthread.h> #endif using namespace lldb_private; @@ -181,6 +182,13 @@ void Log::Warning(const char *format, .. Printf("warning: %s", Content.c_str()); } +void Log::Initialize() { +#ifdef LLVM_ON_UNIX + pthread_atfork(&Log::LockAllChannels, &Log::UnlockAllChannels, &Log::UnlockAllChannels); +#endif + InitializeLldbChannel(); +} + void Log::Register(llvm::StringRef name, Channel &channel) { auto iter = g_channel_map->try_emplace(name, channel); assert(iter.second == true); @@ -321,3 +329,13 @@ void Log::Format(llvm::StringRef file, l message << payload << "\n"; WriteMessage(message.str()); } + +void Log::LockAllChannels() { + for (auto &c: *g_channel_map) + c.second.m_mutex.lock(); +} + +void Log::UnlockAllChannels() { + for (auto &c: *g_channel_map) + c.second.m_mutex.unlock(); +} Modified: lldb/trunk/source/Utility/Logging.cpp URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Utility/Logging.cpp?rev=316173&r1=316172&r2=316173&view=diff ============================================================================== --- lldb/trunk/source/Utility/Logging.cpp (original) +++ lldb/trunk/source/Utility/Logging.cpp Thu Oct 19 10:40:51 2017 @@ -51,7 +51,7 @@ static constexpr Log::Category g_categor static Log::Channel g_log_channel(g_categories, LIBLLDB_LOG_DEFAULT); -void lldb_private::InitializeLog() { +void lldb_private::InitializeLldbChannel() { Log::Register("lldb", g_log_channel); } _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
