comments

db/dur.cpp

@@ -17,7 +17,7 @@
 */
 
 /*
-   phases
+   phases:
 
      PREPLOGBUFFER
        we will build an output buffer ourself and then use O_DIRECT
@@ -36,6 +36,22 @@
        there could be a slow down immediately after remapping as fresh copy-on-writes for commonly written pages will
          be required.  so doing these remaps fractionally is helpful. 
 
+   mutexes:
+
+     READLOCK dbMutex
+     LOCK groupCommitMutex
+       PREPLOGBUFFER()
+     READLOCK mmmutex
+       commitJob.reset()
+     UNLOCK dbMutex                                     // now other threads can write
+       WRITETOJOURNAL()
+       WRITETODATAFILES()
+     UNLOCK mmmutex
+     UNLOCK groupCommitMutex
+
+     on the next write lock acquisition for dbMutex:    // see MongoMutex::_acquiredWriteLock()
+       REMAPPRIVATEVIEW()
+
      @see https://docs.google.com/drawings/edit?id=1TklsmZzm7ohIZkwgeK6rMvsdaR13KjtJYMsfLr175Zc
 */
 
@@ -581,7 +597,7 @@ namespace mongo {
                 // this needs done in a write lock (as there is a short window during remapping when each view 
                 // might not exist) thus we do it on the next acquisition of that instead of here (there is no 
                 // rush if you aren't writing anyway -- but it must happen, if it is done, before any uncommitted 
-                // writes occur).  If desired, perhpas this can be eliminated on posix as it may be that the remap 
+                // writes occur).  If desired, perhaps this can be eliminated on posix as it may be that the remap 
                 // is race-free there.
                 //
                 dbMutex._remapPrivateViewRequested = true;