repro sample for switchbrew/switch-examples#69

Makefile

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+#---------------------------------------------------------------------------------
+.SUFFIXES:
+#---------------------------------------------------------------------------------
+
+ifeq ($(strip $(DEVKITPRO)),)
+$(error "Please set DEVKITPRO in your environment. export DEVKITPRO=<path to>/devkitpro")
+endif
+
+TOPDIR ?= $(CURDIR)
+include $(DEVKITPRO)/libnx/switch_rules
+
+#---------------------------------------------------------------------------------
+# TARGET is the name of the output
+# BUILD is the directory where object files & intermediate files will be placed
+# SOURCES is a list of directories containing source code
+# DATA is a list of directories containing data files
+# INCLUDES is a list of directories containing header files
+# ROMFS is the directory containing data to be added to RomFS, relative to the Makefile (Optional)
+#
+# NO_ICON: if set to anything, do not use icon.
+# NO_NACP: if set to anything, no .nacp file is generated.
+# APP_TITLE is the name of the app stored in the .nacp file (Optional)
+# APP_AUTHOR is the author of the app stored in the .nacp file (Optional)
+# APP_VERSION is the version of the app stored in the .nacp file (Optional)
+# APP_TITLEID is the titleID of the app stored in the .nacp file (Optional)
+# ICON is the filename of the icon (.jpg), relative to the project folder.
+#   If not set, it attempts to use one of the following (in this order):
+#     - <Project name>.jpg
+#     - icon.jpg
+#     - <libnx folder>/default_icon.jpg
+#
+# CONFIG_JSON is the filename of the NPDM config file (.json), relative to the project folder.
+#   If not set, it attempts to use one of the following (in this order):
+#     - <Project name>.json
+#     - config.json
+#   If a JSON file is provided or autodetected, an ExeFS PFS0 (.nsp) is built instead
+#   of a homebrew executable (.nro). This is intended to be used for sysmodules.
+#   NACP building is skipped as well.
+#---------------------------------------------------------------------------------
+TARGET		:=	$(notdir $(CURDIR))
+BUILD		:=	build
+SOURCES		:=	source
+DATA		:=	data
+INCLUDES	:=	include
+#ROMFS	:=	romfs
+
+#---------------------------------------------------------------------------------
+# options for code generation
+#---------------------------------------------------------------------------------
+ARCH	:=	-march=armv8-a+crc+crypto -mtune=cortex-a57 -mtp=soft -fPIE
+
+CFLAGS	:=	-g -Wall -O2 -ffunction-sections \
+			$(ARCH) $(DEFINES)
+
+CFLAGS	+=	$(INCLUDE) -D__SWITCH__
+
+CXXFLAGS	:= $(CFLAGS) -std=c++14 -fno-rtti -fno-exceptions
+
+ASFLAGS	:=	-g $(ARCH)
+LDFLAGS	=	-specs=$(DEVKITPRO)/libnx/switch.specs -g $(ARCH) -Wl,-Map,$(notdir $*.map)
+
+LIBS	:= -lnx
+
+#---------------------------------------------------------------------------------
+# list of directories containing libraries, this must be the top level containing
+# include and lib
+#---------------------------------------------------------------------------------
+LIBDIRS	:= $(PORTLIBS) $(LIBNX)
+
+
+#---------------------------------------------------------------------------------
+# no real need to edit anything past this point unless you need to add additional
+# rules for different file extensions
+#---------------------------------------------------------------------------------
+ifneq ($(BUILD),$(notdir $(CURDIR)))
+#---------------------------------------------------------------------------------
+
+export OUTPUT	:=	$(CURDIR)/$(TARGET)
+export TOPDIR	:=	$(CURDIR)
+
+export VPATH	:=	$(foreach dir,$(SOURCES),$(CURDIR)/$(dir)) \
+			$(foreach dir,$(DATA),$(CURDIR)/$(dir))
+
+export DEPSDIR	:=	$(CURDIR)/$(BUILD)
+
+CFILES		:=	$(foreach dir,$(SOURCES),$(notdir $(wildcard $(dir)/*.c)))
+CPPFILES	:=	$(foreach dir,$(SOURCES),$(notdir $(wildcard $(dir)/*.cpp)))
+SFILES		:=	$(foreach dir,$(SOURCES),$(notdir $(wildcard $(dir)/*.s)))
+BINFILES	:=	$(foreach dir,$(DATA),$(notdir $(wildcard $(dir)/*.*)))
+
+#---------------------------------------------------------------------------------
+# use CXX for linking C++ projects, CC for standard C
+#---------------------------------------------------------------------------------
+ifeq ($(strip $(CPPFILES)),)
+#---------------------------------------------------------------------------------
+	export LD	:=	$(CC)
+#---------------------------------------------------------------------------------
+else
+#---------------------------------------------------------------------------------
+	export LD	:=	$(CXX)
+#---------------------------------------------------------------------------------
+endif
+#---------------------------------------------------------------------------------
+
+export OFILES_BIN	:=	$(addsuffix .o,$(BINFILES))
+export OFILES_SRC	:=	$(CPPFILES:.cpp=.o) $(CFILES:.c=.o) $(SFILES:.s=.o)
+export OFILES 	:=	$(OFILES_BIN) $(OFILES_SRC)
+export HFILES_BIN	:=	$(addsuffix .h,$(subst .,_,$(BINFILES)))
+
+export INCLUDE	:=	$(foreach dir,$(INCLUDES),-I$(CURDIR)/$(dir)) \
+			$(foreach dir,$(LIBDIRS),-I$(dir)/include) \
+			-I$(CURDIR)/$(BUILD)
+
+export LIBPATHS	:=	$(foreach dir,$(LIBDIRS),-L$(dir)/lib)
+
+ifeq ($(strip $(CONFIG_JSON)),)
+	jsons := $(wildcard *.json)
+	ifneq (,$(findstring $(TARGET).json,$(jsons)))
+		export APP_JSON := $(TOPDIR)/$(TARGET).json
+	else
+		ifneq (,$(findstring config.json,$(jsons)))
+			export APP_JSON := $(TOPDIR)/config.json
+		endif
+	endif
+else
+	export APP_JSON := $(TOPDIR)/$(CONFIG_JSON)
+endif
+
+ifeq ($(strip $(ICON)),)
+	icons := $(wildcard *.jpg)
+	ifneq (,$(findstring $(TARGET).jpg,$(icons)))
+		export APP_ICON := $(TOPDIR)/$(TARGET).jpg
+	else
+		ifneq (,$(findstring icon.jpg,$(icons)))
+			export APP_ICON := $(TOPDIR)/icon.jpg
+		endif
+	endif
+else
+	export APP_ICON := $(TOPDIR)/$(ICON)
+endif
+
+ifeq ($(strip $(NO_ICON)),)
+	export NROFLAGS += --icon=$(APP_ICON)
+endif
+
+ifeq ($(strip $(NO_NACP)),)
+	export NROFLAGS += --nacp=$(CURDIR)/$(TARGET).nacp
+endif
+
+ifneq ($(APP_TITLEID),)
+	export NACPFLAGS += --titleid=$(APP_TITLEID)
+endif
+
+ifneq ($(ROMFS),)
+	export NROFLAGS += --romfsdir=$(CURDIR)/$(ROMFS)
+endif
+
+.PHONY: $(BUILD) clean all
+
+#---------------------------------------------------------------------------------
+all: $(BUILD)
+
+$(BUILD):
+	@[ -d $@ ] || mkdir -p $@
+	@$(MAKE) --no-print-directory -C $(BUILD) -f $(CURDIR)/Makefile
+
+#---------------------------------------------------------------------------------
+clean:
+	@echo clean ...
+ifeq ($(strip $(APP_JSON)),)
+	@rm -fr $(BUILD) $(TARGET).nro $(TARGET).nacp $(TARGET).elf
+else
+	@rm -fr $(BUILD) $(TARGET).nsp $(TARGET).nso $(TARGET).npdm $(TARGET).elf
+endif
+
+
+#---------------------------------------------------------------------------------
+else
+.PHONY:	all
+
+DEPENDS	:=	$(OFILES:.o=.d)
+
+#---------------------------------------------------------------------------------
+# main targets
+#---------------------------------------------------------------------------------
+ifeq ($(strip $(APP_JSON)),)
+
+all	:	$(OUTPUT).nro
+
+ifeq ($(strip $(NO_NACP)),)
+$(OUTPUT).nro	:	$(OUTPUT).elf $(OUTPUT).nacp
+else
+$(OUTPUT).nro	:	$(OUTPUT).elf
+endif
+
+else
+
+all	:	$(OUTPUT).nsp
+
+$(OUTPUT).nsp	:	$(OUTPUT).nso $(OUTPUT).npdm
+
+$(OUTPUT).nso	:	$(OUTPUT).elf
+
+endif
+
+$(OUTPUT).elf	:	$(OFILES)
+
+$(OFILES_SRC)	: $(HFILES_BIN)
+
+#---------------------------------------------------------------------------------
+# you need a rule like this for each extension you use as binary data
+#---------------------------------------------------------------------------------
+%.bin.o	%_bin.h :	%.bin
+#---------------------------------------------------------------------------------
+	@echo $(notdir $<)
+	@$(bin2o)
+
+-include $(DEPENDS)
+
+#---------------------------------------------------------------------------------------
+endif
+#---------------------------------------------------------------------------------------

README.md

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+This is a reproduction on randomly freezing threads on libnx.
+
+The thread pool implementation is taken from https://www.youtube.com/watch?v=eWTGtp3HXiw, but this also happens when using normal std::threads, pthreads and libnx threads. This is just the implementation I use in my app. (I tried the other ones in my app though, too, with the same random freezes.)
+
+Instructions:
+
+1. Load up hbmenu and press Y to get NetLoader
+2. run `make clean all && while true; do nxlink -s *.nro*; done` (You might need to set `-a <switch IP>` on nxlink)
+3. The app will run and dump stdio to your terminal
+4. It will run and quit successfully if it did not freeze. So press Y on the switch to load the app again.
+5. At some point it will freeze after spawning a new thread.
+6. ??? This is where I am stuck. No idea how to debug this further.

include/ThreadPool.hpp

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+#pragma once
+#include <condition_variable>
+#include <functional>
+#include <iostream>
+#include <future>
+#include <vector>
+#include <thread>
+#include <queue>
+#include <switch.h>
+
+using Task = std::function<void()>;
+class ThreadPool
+{
+public:
+
+    explicit ThreadPool(std::size_t numThreads);
+
+    ~ThreadPool();
+
+    template<class T>
+    auto enqueue(T task)->std::future<decltype(task())>
+    {
+        printf("enq\n");
+        auto wrapper = std::make_shared<std::packaged_task<decltype(task()) ()>>(std::move(task));
+
+        {
+            std::unique_lock<std::mutex> lock{mEventMutex};
+            mTasks.emplace([=] {
+                (*wrapper)();
+            });
+        }
+
+        mEventVar.notify_one();
+        return wrapper->get_future();
+    }
+
+    std::vector<std::thread> mThreads;
+
+    std::condition_variable mEventVar;
+
+    std::mutex mEventMutex;
+    bool mStopping = false;
+
+    std::queue<Task> mTasks;
+
+private:
+    void start(std::size_t numThreads);
+
+    void stop() noexcept;
+};

source/ThreadPool.cpp

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+#include "ThreadPool.hpp"
+
+ThreadPool::ThreadPool(std::size_t numThreads)
+{
+    start(numThreads);
+}
+
+ThreadPool::~ThreadPool()
+{
+    stop();
+}
+
+void ThreadPool::start(std::size_t numThreads)
+{
+    for (auto i = 0u; i < numThreads; ++i)
+    {
+        printf("spawning thread %d/%d\n", i + 1, numThreads);
+        mThreads.emplace_back([=]{
+            u32 prio;
+            s32 preferred;
+            u32 mask;
+            u64 threadId;
+            Handle h = threadGetCurHandle();
+            svcGetThreadPriority(&prio, h);
+            svcGetThreadId(&threadId, h);
+            svcGetThreadCoreMask(&preferred, &mask, h);
+
+            printf("[%ld] Prio: %x, preferred CPU: %d, mask: %x\n", threadId, prio, preferred, mask);
+
+            while (true)
+            {
+                Task task;
+
+                {
+                    std::unique_lock<std::mutex> lock{mEventMutex};
+
+                    mEventVar.wait(lock, [=] { return mStopping || !mTasks.empty(); });
+
+                    if (mStopping && mTasks.empty())
+                        break;
+
+                    task = std::move(mTasks.front());
+                    mTasks.pop();
+                }
+
+                printf("running in thread\n");
+                task();
+            }
+        });
+        printf("spawned thread %d/%d\n", i + 1, numThreads);
+    }
+    printf("all threads\n");
+}
+
+void ThreadPool::stop() noexcept
+{
+    {
+        std::unique_lock<std::mutex> lock{mEventMutex};
+        mStopping = true;
+    }
+
+    mEventVar.notify_all();
+
+    for (auto &thread : mThreads) {
+        thread.join();
+    }
+}
+
+//int main()
+//{
+//    {
+//        ThreadPool pool{36};
+//
+//        for (auto i = 0; i < 36; ++i)
+//        {
+//            pool.enqueue([] {
+//                auto f = 1000000000;
+//                while (f > 1)
+//                    f /= 1.00000001;
+//            });
+//        }
+//    }
+//
+//    return 0;
+//}