add operator->() to atomic pointers

use atomic<> for dir pointer in an inode

add operator->() to atomic pointers
009a6d08 · Nickolai Zeldovich · 392bdc80 · 009a6d08 · 009a6d08 · 009a6d08
--- a/atomic_2.h
+++ b/atomic_2.h
@@ -464,6 +464,14 @@ namespace __atomic2
      { return load(); }
      __pointer_type
+      operator->() const
+      { return load(); }
+      __pointer_type
+      operator->() const volatile
+      { return load(); }
+      __pointer_type
      operator=(__pointer_type __p)
      {
 	store(__p);

--- a/file.hh
+++ b/file.hh
@@ -30,7 +30,7 @@ struct inode : public rcu_freed {
  struct condvar cv;
  struct spinlock lock;
  char lockname[16];
-  xns<strbuf<DIRSIZ>, u32, namehash> *dir;
+  atomic<xns<strbuf<DIRSIZ>, u32, namehash>*> dir;
  short type;         // copy of disk inode
  short major;

--- a/fs.cc
+++ b/fs.cc
@@ -643,7 +643,9 @@ dir_init(struct inode *dp)
    }
    brelse(bp, 0);
  }
-  if (!__sync_bool_compare_and_swap(&dp->dir, 0, dir)) {
+  decltype(dir) expect_null = 0;
+  if (!dp->dir.compare_exchange_strong(expect_null, dir)) {
    // XXX free all the dirents
    delete dir;
  }