Set worker thread stack size to match the main thread

src/support/threads.cpp

@@ -19,6 +19,7 @@
 #include <algorithm>
 #include <iostream>
 #include <string>
+#include <system_error>
 
 #ifdef __linux__
 #include <sched.h> // For sched_getaffinity
@@ -29,6 +30,12 @@
 #include "threads.h"
 #include "utilities.h"
 
+#ifdef BINARYEN_PTHREAD_WORKERS
+#include <limits.h>
+#include <sys/resource.h>
+#include <unistd.h>
+#endif
+
 // debugging tools
 
 // DEBUG_TYPE is for BYN_TRACE macro.  This tracing can be enabled at runtime
@@ -60,6 +67,61 @@ namespace wasm {
 
 // Thread
 
+#ifdef BINARYEN_PTHREAD_WORKERS
+
+size_t getWorkerThreadStackSize() {
+  static const size_t size = []() -> size_t {
+    // Matches glibc's default for new threads, which also falls back to a
+    // fixed size when the limit is unbounded.
+    const size_t defaultSize = 8 * 1024 * 1024;
+    struct rlimit limit;
+    size_t size = defaultSize;
+    if (getrlimit(RLIMIT_STACK, &limit) == 0 &&
+        limit.rlim_cur != RLIM_INFINITY) {
+      size = limit.rlim_cur;
+    }
+    size = std::max(size, size_t(PTHREAD_STACK_MIN));
+    // Some platforms (macOS) require a page-aligned size.
+    long page = sysconf(_SC_PAGESIZE);
+    if (page > 0) {
+      size = (size + page - 1) / page * page;
+    }
+    return size;
+  }();
+  return size;
+}
+
+static void* threadEntry(void* self) {
+  Thread::mainLoop(self);
+  return nullptr;
+}
+
+Thread::Thread(ThreadPool* parent) : parent(parent) {
+  assert(!parent->isRunning());
+  pthread_attr_t attr;
+  pthread_attr_init(&attr);
+  pthread_attr_setstacksize(&attr, getWorkerThreadStackSize());
+  int err = pthread_create(&thread, &attr, threadEntry, this);
+  pthread_attr_destroy(&attr);
+  if (err != 0) {
+    throw std::system_error(err, std::generic_category());
+  }
+}
+
+Thread::~Thread() {
+  {
+    std::lock_guard<std::mutex> lock(mutex);
+    // notify the thread that it can exit
+    done = true;
+    condition.notify_one();
+  }
+  pthread_join(thread, nullptr);
+}
+
+#else
+
+size_t getWorkerThreadStackSize() { return 0; }
+
 Thread::Thread(ThreadPool* parent) : parent(parent) {
   assert(!parent->isRunning());
   thread = std::make_unique<std::thread>(mainLoop, this);
@@ -75,6 +137,8 @@ Thread::~Thread() {
   thread->join();
 }
 
+#endif // BINARYEN_PTHREAD_WORKERS
+
 void Thread::work(std::function<ThreadWorkState()> doWork_) {
   // TODO: fancy work stealing
   DEBUG_THREAD("send work to thread\n");

src/support/threads.h

@@ -32,6 +32,15 @@
 
 #include "compiler-support.h"
 
+// On POSIX we create worker threads with pthreads directly so that we can set
+// their stack size to match the main thread. std::thread uses the platform
+// default, which on macOS is only 512KB for secondary threads (Linux uses
+// RLIMIT_STACK, and Windows uses the linker's /STACK for all threads).
+#if !defined(_WIN32) && !defined(__EMSCRIPTEN__)
+#define BINARYEN_PTHREAD_WORKERS 1
+#include <pthread.h>
+#endif
+
 namespace wasm {
 
 // The work state of a helper thread - is there more to do,
@@ -48,7 +57,11 @@ class ThreadPool;
 
 class Thread {
   ThreadPool* parent;
+#ifdef BINARYEN_PTHREAD_WORKERS
+  pthread_t thread;
+#else
   std::unique_ptr<std::thread> thread;
+#endif
   std::mutex mutex;
   std::condition_variable condition;
   bool done = false;
@@ -62,10 +75,14 @@ class Thread {
   // it returns false.
   void work(std::function<ThreadWorkState()> doWork);
 
-private:
   static void mainLoop(void* self);
 };
 
+// The stack size requested for worker threads, or 0 if the platform default is
+// used. On POSIX this is the RLIMIT_STACK soft limit, so that workers can
+// recurse as deeply as the main thread and `ulimit -s` applies to them too.
+size_t getWorkerThreadStackSize();
+
 //
 // A pool of helper threads.
 //

test/gtest/CMakeLists.txt

@@ -38,6 +38,7 @@ set(unittest_SOURCES
   stringify.cpp
   subtype-exprs.cpp
   suffix_tree.cpp
+  threads.cpp
   topological-sort.cpp
   type-builder.cpp
   type-updating.cpp

test/gtest/threads.cpp

@@ -0,0 +1,51 @@
+#include "support/threads.h"
+#include "gtest/gtest.h"
+
+#ifdef BINARYEN_PTHREAD_WORKERS
+
+#include <pthread.h>
+
+using namespace wasm;
+
+namespace {
+
+size_t getCurrentThreadStackSize() {
+#ifdef __APPLE__
+  return pthread_get_stacksize_np(pthread_self());
+#else
+  pthread_attr_t attr;
+  if (pthread_getattr_np(pthread_self(), &attr) != 0) {
+    return 0;
+  }
+  size_t size = 0;
+  pthread_attr_getstacksize(&attr, &size);
+  pthread_attr_destroy(&attr);
+  return size;
+#endif
+}
+
+} // anonymous namespace
+
+TEST(ThreadsTest, WorkerStackSize) {
+  auto* pool = ThreadPool::get();
+  size_t numThreads = pool->size();
+  if (numThreads == 1) {
+    GTEST_SKIP() << "no worker threads";
+  }
+  std::vector<size_t> sizes(numThreads);
+  std::vector<std::function<ThreadWorkState()>> workers;
+  for (size_t i = 0; i < numThreads; i++) {
+    workers.push_back([&sizes, i]() {
+      sizes[i] = getCurrentThreadStackSize();
+      return ThreadWorkState::Finished;
+    });
+  }
+  pool->work(workers);
+  size_t expected = getWorkerThreadStackSize();
+  ASSERT_GT(expected, 0u);
+  for (auto size : sizes) {
+    EXPECT_GE(size, expected);
+  }
+}
+
+#endif // BINARYEN_PTHREAD_WORKERS