From 9e2d64b8d38b012e653ceee5d245de4555a3b552 Mon Sep 17 00:00:00 2001
From: drh <drh@noemail.net>
Date: Fri, 26 Sep 2008 20:02:50 +0000
Subject: [PATCH] Make sure the queueMutex is held prior to writing the
 pQueueLast field of the write queue in the async demonstration code.  Ticket
 #3405. (CVS 5744)

FossilOrigin-Name: 5622a1e285fc4d5720f7180a0eb551952f2df331
---
 manifest         | 14 +++++++-------
 manifest.uuid    |  2 +-
 src/test_async.c | 27 ++++++++++++++++++++++++++-
 3 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/manifest b/manifest
index d52ce8976e..910fb3ee23 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Performance\senhancement:\savoid\scalling\sreparentChildPages()\sfrom\sbalance_nonroot().\s(CVS\s5743)
-D 2008-09-26T17:31:55
+C Make\ssure\sthe\squeueMutex\sis\sheld\sprior\sto\swriting\sthe\spQueueLast\sfield\nof\sthe\swrite\squeue\sin\sthe\sasync\sdemonstration\scode.\s\sTicket\s#3405.\s(CVS\s5744)
+D 2008-09-26T20:02:50
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in e4ab842f9a64ef61d57093539a8aab76b12810db
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -165,7 +165,7 @@ F src/test6.c 0a0304a69cfa4962a429d084c6d451ff9e4fb572
 F src/test7.c 475b1fa7e3275408b40a3cbdc9508cbdc41ffa02
 F src/test8.c 3637439424d0d21ff2dcf9b015c30fcc1e7bcb24
 F src/test9.c 904ebe0ed1472d6bad17a81e2ecbfc20017dc237
-F src/test_async.c de6661370d96f660e0f0d604582c193c6144b19c
+F src/test_async.c 45024094ed7cf780c5d5dccda645145f95cf78ef
 F src/test_autoext.c f53b0cdf7bf5f08100009572a5d65cdb540bd0ad
 F src/test_btree.c 8d5b835054f1dd15992e09864a8bc04386bab701
 F src/test_config.c db72e95bafdd53c05ceb8735f833cc5dc1f48782
@@ -637,7 +637,7 @@ F tool/speedtest16.c c8a9c793df96db7e4933f0852abb7a03d48f2e81
 F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 1dbced29de5f59ba2ebf877edcadf171540374d1
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
-P 5debf12fa46520946ac5da44c03448fffbc9940c
-R ad8baa95733fbb9a312a15654e608ce1
-U danielk1977
-Z 410e2e4a76b6dc0451fd1f6a24aebc75
+P 28fd0a50ca8529892f5b1ababd38d494889eed6d
+R 42f79e8d6bad8dc05f28b70884a1cf00
+U drh
+Z c1f39a8806852672a67f740f0e33cd9d
diff --git a/manifest.uuid b/manifest.uuid
index 2f22cb8c72..1f441bd728 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-28fd0a50ca8529892f5b1ababd38d494889eed6d
\ No newline at end of file
+5622a1e285fc4d5720f7180a0eb551952f2df331
\ No newline at end of file
diff --git a/src/test_async.c b/src/test_async.c
index 77da3149c0..44e445ea1f 100644
--- a/src/test_async.c
+++ b/src/test_async.c
@@ -10,7 +10,7 @@
 **
 *************************************************************************
 **
-** $Id: test_async.c,v 1.47 2008/09/15 15:49:34 danielk1977 Exp $
+** $Id: test_async.c,v 1.48 2008/09/26 20:02:50 drh Exp $
 **
 ** This file contains an example implementation of an asynchronous IO 
 ** backend for SQLite.
@@ -571,12 +571,31 @@ static int async_cond_wait(pthread_cond_t *pCond, pthread_mutex_t *pMutex){
   return rc;
 }
 
+/*
+** Assert that the mutex is held by the current thread.
+*/
+static void assert_mutex_is_held(pthread_mutex_t *pMutex){
+  int iIdx;
+  pthread_mutex_t *aMutex = (pthread_mutex_t *)(&async);
+  pthread_t *aHolder = (pthread_t *)(&asyncdebug);
+
+  for(iIdx=0; iIdx<3; iIdx++){
+    if( pMutex==&aMutex[iIdx] ) break;
+  }
+  assert(iIdx<3);
+  assert( aHolder[iIdx]==pthread_self() );
+}
+
 /* Call our async_XX wrappers instead of selected pthread_XX functions */
 #define pthread_mutex_lock    async_mutex_lock
 #define pthread_mutex_unlock  async_mutex_unlock
 #define pthread_mutex_trylock async_mutex_trylock
 #define pthread_cond_wait     async_cond_wait
 
+#else    /* if defined(NDEBUG) */
+
+#define assert_mutex_is_held(X)    /* A no-op when not debugging */
+
 #endif   /* !defined(NDEBUG) */
 
 /*
@@ -1482,6 +1501,11 @@ static void *asyncWriterThread(void *pIsStarted){
         rc = unlinkAsyncFile(pData);
         pthread_mutex_unlock(&async.lockMutex);
 
+        if( !holdingMutex ){
+          pthread_mutex_lock(&async.queueMutex);
+          holdingMutex = 1;
+        }
+        assert_mutex_is_held(&async.queueMutex);
         async.pQueueFirst = p->pNext;
         sqlite3_free(pData);
         doNotFree = 1;
@@ -1534,6 +1558,7 @@ static void *asyncWriterThread(void *pIsStarted){
       async.pQueueLast = 0;
     }
     if( !doNotFree ){
+      assert_mutex_is_held(&async.queueMutex);
       async.pQueueFirst = p->pNext;
       sqlite3_free(p);
     }
-- 
2.47.2