posix: posix_thread: allocate stack manually

Otherwise, the stack is allocated on the creating thread and destroyed
on the created thread, which we don't support.

core/posix.cc

@@ -3,6 +3,7 @@
  */
 
 #include "posix.hh"
+#include "align.hh"
 #include <sys/mman.h>
 
 void mmap_deleter::operator()(void* ptr) const {
@@ -21,8 +22,34 @@ void* posix_thread::start_routine(void* arg) {
     return nullptr;
 }
 
-posix_thread::posix_thread(std::function<void ()> func) : _func(std::make_unique<std::function<void ()>>(std::move(func))) {
-    auto r = pthread_create(&_pthread, nullptr,
+posix_thread::posix_thread(std::function<void ()> func)
+    : posix_thread(attr{}, std::move(func)) {
+}
+
+posix_thread::posix_thread(attr a, std::function<void ()> func)
+    : _func(std::make_unique<std::function<void ()>>(std::move(func))) {
+    pthread_attr_t pa;
+    auto r = pthread_attr_init(&pa);
+    if (r) {
+        throw std::system_error(r, std::system_category());
+    }
+    auto stack_size = a._stack_size.size;
+    if (!stack_size) {
+        stack_size = 2 << 20;
+    }
+    // allocate guard area as well
+    _stack = mmap_anonymous(nullptr, stack_size + (4 << 20),
+            PROT_NONE, MAP_PRIVATE | MAP_NORESERVE);
+    auto stack_start = align_up(_stack.get() + 1, 2 << 20);
+    mmap_area real_stack = mmap_anonymous(stack_start, stack_size,
+            PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_FIXED | MAP_STACK);
+    real_stack.release(); // protected by @_stack
+    ::madvise(stack_start, stack_size, MADV_HUGEPAGE);
+    r = pthread_attr_setstack(&pa, stack_start, stack_size);
+    if (r) {
+        throw std::system_error(r, std::system_category());
+    }
+    r = pthread_create(&_pthread, &pa,
                 &posix_thread::start_routine, _func.get());
     if (r) {
         throw std::system_error(r, std::system_category());
@@ -30,7 +57,8 @@ posix_thread::posix_thread(std::function<void ()> func) : _func(std::make_unique
 }
 
 posix_thread::posix_thread(posix_thread&& x)
-    : _func(std::move(x._func)), _pthread(x._pthread), _valid(x._valid) {
+    : _func(std::move(x._func)), _pthread(x._pthread), _valid(x._valid)
+    , _stack(std::move(x._stack)) {
     x._valid = false;
 }
 

core/posix.hh

@@ -195,17 +195,42 @@ using mmap_area = std::unique_ptr<char[], mmap_deleter>;
 mmap_area mmap_anonymous(void* addr, size_t length, int prot, int flags);
 
 class posix_thread {
+public:
+    class attr;
+private:
     // must allocate, since this class is moveable
     std::unique_ptr<std::function<void ()>> _func;
     pthread_t _pthread;
     bool _valid = true;
+    mmap_area _stack;
 private:
     static void* start_routine(void* arg);
 public:
     posix_thread(std::function<void ()> func);
+    posix_thread(attr a, std::function<void ()> func);
     posix_thread(posix_thread&& x);
     ~posix_thread();
     void join();
+public:
+    class attr {
+    public:
+        struct stack_size { size_t size = 0; };
+        attr() = default;
+        template <typename... A>
+        attr(A... a) {
+            set(std::forward<A>(a)...);
+        }
+        void set() {}
+        template <typename A, typename... Rest>
+        void set(A a, Rest... rest) {
+            set(std::forward<A>(a));
+            set(std::forward<Rest>(rest)...);
+        }
+        void set(stack_size ss) { _stack_size = ss; }
+    private:
+        stack_size _stack_size;
+        friend class posix_thread;
+    };
 };