Add locks to FileStream

mlx/backend/io/primitives.cpp

@@ -35,8 +35,12 @@ void Load::eval_io(
   array& out = outputs[0];
   out.set_data(allocator::malloc_or_wait(out.nbytes()));
 
-  reader_->seek(offset_, std::ios_base::beg);
-  reader_->read(out.data<char>(), out.nbytes());
+  {
+    std::lock_guard lock(*reader_);
+
+    reader_->seek(offset_, std::ios_base::beg);
+    reader_->read(out.data<char>(), out.nbytes());
+  }
 
   if (swap_endianness_) {
     switch (out.itemsize()) {

mlx/io/load.h

@@ -20,6 +20,8 @@ class Reader {
       std::ios_base::seekdir way = std::ios_base::beg) = 0;
   virtual void read(char* data, size_t n) = 0;
   virtual std::string label() const = 0;
+  virtual void lock() = 0;
+  virtual void unlock() = 0;
 };
 
 class Writer {
@@ -67,9 +69,18 @@ class FileReader : public Reader {
     return "file " + label_;
   }
 
+  void lock() override {
+    is_mutex_.lock();
+  }
+
+  void unlock() override {
+    is_mutex_.unlock();
+  }
+
  private:
   std::ifstream is_;
   std::string label_;
+  std::mutex is_mutex_;
 };
 
 class FileWriter : public Writer {

python/src/load.cpp

@@ -150,11 +150,21 @@ class PyFileReader : public io::Reader {
     return "python file object";
   }
 
+  void lock() override {
+    stream_mutex_.lock();
+  }
+
+  void unlock() override {
+    stream_mutex_.unlock();
+  }
+
  private:
   nb::object pyistream_;
   nb::object readinto_func_;
   nb::object seek_func_;
   nb::object tell_func_;
+
+  std::mutex stream_mutex_;
 };
 
 std::pair<