Fix deadlock problem in the unix mutex. Ticket #1672. (CVS 3071)

FossilOrigin-Name: a6c30be214bb575f9ecfa299b7a597d21e3d3aca

manifest

@@ -1,5 +1,5 @@
-C Add\sa\ssymbol\sP3_TRANSIENT\sto\spass\sto\sVdbeSetColName()\sto\smake\sit\scopy\sthe\sstring\sparameter\sup\sto\sthe\sfirst\s0\sbyte.\s(CVS\s3070)
-D 2006-02-10T03:06:10
+C Fix\sdeadlock\sproblem\sin\sthe\sunix\smutex.\s\sTicket\s#1672.\s(CVS\s3071)
+D 2006-02-10T04:33:12
 F Makefile.in 5d8dff443383918b700e495de42ec65bc1c8865b
 F Makefile.linux-gcc 74ba0eadf88748a9ce3fd03d2a3ede2e6715baec
 F README 9c4e2d6706bdcc3efdd773ce752a8cdab4f90028
@@ -55,7 +55,7 @@ F src/os.h 93035a0e3b9dd05cdd0aaef32ea28ca28e02fe78
 F src/os_common.h 108cd719c96a2b714b64e02aeabbd40684274e6a
 F src/os_test.c 49833426101f99aee4bb5f6a44b7c4b2029fda1c
 F src/os_test.h 903c93554c23d88f34f667f1979e4a1cee792af3
-F src/os_unix.c dfd3b03ab09a43d50d0fabc3bca7b0796512d088
+F src/os_unix.c 50e51ba8a78e4a26850d77b077f0d43a5036a76c
 F src/os_unix.h 5768d56d28240d3fe4537fac08cc85e4fb52279e
 F src/os_win.c c67a2c46d929cf54c8f80ec5e6079cf684a141a9
 F src/os_win.h 41a946bea10f61c158ce8645e7646b29d44f122b
@@ -351,7 +351,7 @@ F www/tclsqlite.tcl bb0d1357328a42b1993d78573e587c6dcbc964b9
 F www/vdbe.tcl 87a31ace769f20d3627a64fa1fade7fed47b90d0
 F www/version3.tcl a99cf5f6d8bd4d5537584a2b342f0fb9fa601d8b
 F www/whentouse.tcl 97e2b5cd296f7d8057e11f44427dea8a4c2db513
-P 82f502cdc1fead3bf7e3190d5c9db3aee6919ed4
-R e8ab349255445085d0fedc02cdd56499
-U danielk1977
-Z 91cde64b2b17550c6eb4505abb4035ed
+P 6ebb8f9bb2f6a3f7fde19267727aa4e2d878a416
+R f2123b74208f8dc7a90c193c43dfdac6
+U drh
+Z 902f2f44199cd95ee9b139b42f49b143

manifest.uuid

@@ -1 +1 @@
-6ebb8f9bb2f6a3f7fde19267727aa4e2d878a416
+a6c30be214bb575f9ecfa299b7a597d21e3d3aca

src/os_unix.c

@@ -1670,13 +1670,30 @@ int sqlite3UnixSleep(int ms){
 }
 
 /*
-** Static variables used for thread synchronization
+** Static variables used for thread synchronization.
+**
+** inMutex      the nesting depth of the recursive mutex.  The thread
+**              holding mutexMain can read this variable at any time.
+**              But is must hold mutexAux to change this variable.  Other
+**              threads must hold mutexAux to read the variable.
+**
+** mutexOwner   The thread id of the thread holding mutexMain.  Same
+**              access rules as for inMutex.
+**
+** mutexOwnerValid   True if the value in mutexOwner is valid.  
+**
+** mutexMain    The main mutex.  Hold this mutex in order to get exclusive
+**              access to SQLite data structures.
+**
+** mutexAux     An auxiliary mutex needed to access variables defined above.
+**
 */
 static int inMutex = 0;
 #ifdef SQLITE_UNIX_THREADS
-static pthread_t mutexOwner;
-static pthread_mutex_t mutex1 = PTHREAD_MUTEX_INITIALIZER;
-static pthread_mutex_t mutex2 = PTHREAD_MUTEX_INITIALIZER;
+static pthread_t mutexOwner;          /* Thread holding the mutex */
+static int mutexOwnerValid = 0;       /* True if mutexOwner is valid */
+static pthread_mutex_t mutexMain = PTHREAD_MUTEX_INITIALIZER; /* The mutex */
+static pthread_mutex_t mutexAux = PTHREAD_MUTEX_INITIALIZER;  /* Aux mutex */
 #endif
 
 /*
@@ -1691,25 +1708,34 @@ static pthread_mutex_t mutex2 = PTHREAD_MUTEX_INITIALIZER;
 */
 void sqlite3UnixEnterMutex(){
 #ifdef SQLITE_UNIX_THREADS
-  pthread_mutex_lock(&mutex1);
-  if( inMutex==0 ){
-    pthread_mutex_lock(&mutex2);
+  pthread_mutex_lock(&mutexAux);
+  if( !mutexOwnerValid || !pthread_equal(mutexOwner, pthread_self()) ){
+    pthread_mutex_unlock(&mutexAux);
+    pthread_mutex_lock(&mutexMain);
+    assert( inMutex==0 );
+    assert( !mutexOwnerValid );
+    pthread_mutex_lock(&mutexAux);
     mutexOwner = pthread_self();
+    mutexOwnerValid = 1;
   }
-  pthread_mutex_unlock(&mutex1);
-#endif
   inMutex++;
+  pthread_mutex_unlock(&mutexAux);
+#else
+  inMutex++
+#endif
 }
 void sqlite3UnixLeaveMutex(){
   assert( inMutex>0 );
 #ifdef SQLITE_UNIX_THREADS
-  assert( pthread_equal(mutexOwner, pthread_self()) );
-  pthread_mutex_lock(&mutex1);
+  pthread_mutex_lock(&mutexAux);
   inMutex--;
+  assert( pthread_equal(mutexOwner, pthread_self()) );
   if( inMutex==0 ){
-    pthread_mutex_unlock(&mutex2);
+    assert( mutexOwnerValid );
+    mutexOwnerValid = 0;
+    pthread_mutex_unlock(&mutexMain);
   }
-  pthread_mutex_unlock(&mutex1);
+  pthread_mutex_unlock(&mutexAux);
 #else
   inMutex--;
 #endif
@@ -1718,14 +1744,17 @@ void sqlite3UnixLeaveMutex(){
 /*
 ** Return TRUE if the mutex is currently held.
 **
-** If the thisThreadOnly parameter is true, return true only if the
+** If the thisThrd parameter is true, return true only if the
 ** calling thread holds the mutex.  If the parameter is false, return
 ** true if any thread holds the mutex.
 */
-int sqlite3UnixInMutex(int thisThreadOnly){
+int sqlite3UnixInMutex(int thisThrd){
 #ifdef SQLITE_UNIX_THREADS
-  return inMutex>0 && 
-           (thisThreadOnly==0 || pthread_equal(mutexOwner, pthread_self()));
+  int rc;
+  pthread_mutex_lock(&mutexAux);
+  rc = inMutex>0 && (thisThrd==0 || pthread_equal(mutexOwner,pthread_self()));
+  pthread_mutex_unlock(&mutexAux);
+  return rc;
 #else
   return inMutex>0;
 #endif