A thread-safe, but non-scalable, filetable

cac83063 · Silas Boyd-Wickizer · 229f28b7 · cac83063
--- a/include/filetable.hh
+++ b/include/filetable.hh
@@ -5,6 +5,7 @@ public:
  filetable() : ref_(1) {
    for(int fd = 0; fd < NOFILE; fd++)
      ofile_[fd] = nullptr;
+    initlock(&lock_, "filetable", 0);
  }

  filetable(const filetable &f) : ref_(1) {
@@ -14,6 +15,7 @@ public:
      else
        ofile_[fd] = nullptr;
    }
+    initlock(&lock_, "filetable", 0);
  }
  
  ~filetable() {
@@ -23,29 +25,40 @@ public:
        ofile_[fd] = 0;
      }
    }
+    destroylock(&lock_);
  }

-  struct file *getfile(int fd) {
+  file *getfile(int fd) {
+    file *f;
+
    if (fd < 0 || fd >= NOFILE)
      return nullptr;
-
-    return ofile_[fd];
+    acquire(&lock_);
+    f = ofile_[fd];
+    // XXX(sbw) f->inc();
+    release(&lock_);
+    return f;
  }

  int allocfd(struct file *f) {
-    for (int fd = 0; fd < NOFILE; fd++){
+    acquire(&lock_);
+    for (int fd = 0; fd < NOFILE; fd++) {
      if (ofile_[fd] == nullptr){
        ofile_[fd] = f;
+        release(&lock_);
        return fd;
      }
    }
-    
+    release(&lock_);    
    return -1;
  }

  void close(int fd) {
    struct file *f = ofile_[fd];
+    
+    acquire(&lock_);
    ofile_[fd] = nullptr;
+    release(&lock_);
    f->close();
  }

@@ -63,4 +76,5 @@ public:
 private:
  struct file *ofile_[NOFILE];
  std::atomic<u64> ref_;
+  struct spinlock lock_;
 };