Come to think of it, DropBuffers() could have the same problem as

ReleaseRelationBuffers --- need to wait if anyone is trying to flush
out that buffer.

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 8b71dc2..28b467f 100644 (file)
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.67 1999/11/22 01:19:42 tgl Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.68 1999/11/22 02:03:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -831,7 +831,7 @@ FlushBuffer(Buffer buffer, bool release)
         */
        if (bufHdr->flags & BM_JUST_DIRTIED)
        {
-               elog(NOTICE, "FlusfBuffer: content of block %u (%s) changed while flushing",
+               elog(NOTICE, "FlushBuffer: content of block %u (%s) changed while flushing",
                         bufHdr->tag.blockNum, bufHdr->sb_relname);
        }
        else
@@ -1476,9 +1476,8 @@ ReleaseRelationBuffers(Relation rel)
  *             This function marks all the buffers in the buffer cache for a
  *             particular database as clean.  This is used when we destroy a
  *             database, to avoid trying to flush data to disk when the directory
- *             tree no longer exists.
- *
- *             This is an exceedingly non-public interface.
+ *             tree no longer exists.  Implementation is pretty similar to
+ *             ReleaseRelationBuffers() which is for destroying just one relation.
  * --------------------------------------------------------------------
  */
 void
@@ -1491,8 +1490,30 @@ DropBuffers(Oid dbid)
        for (i = 1; i <= NBuffers; i++)
        {
                buf = &BufferDescriptors[i - 1];
-               if ((buf->tag.relId.dbId == dbid) && (buf->flags & BM_DIRTY))
-                       buf->flags &= ~BM_DIRTY;
+       recheck:
+               if (buf->tag.relId.dbId == dbid)
+               {
+                       /*
+                        * If there is I/O in progress, better wait till it's done;
+                        * don't want to delete the database out from under someone
+                        * who's just trying to flush the buffer!
+                        */
+                       if (buf->flags & BM_IO_IN_PROGRESS)
+                       {
+                               WaitIO(buf, BufMgrLock);
+                               /* By now, the buffer very possibly belongs to some other
+                                * DB, so check again before proceeding.
+                                */
+                               goto recheck;
+                       }
+                       /* Now we can do what we came for */
+                       buf->flags &= ~ ( BM_DIRTY | BM_JUST_DIRTIED);
+                       /*
+                        * The thing should be free, if caller has checked that
+                        * no backends are running in that database.
+                        */
+                       Assert(buf->flags & BM_FREE);
+               }
        }
        SpinRelease(BufMgrLock);
 }