Use recursive mutexes in pthreads. If the pthreads implementation does not

support recursive mutexes, then you cannot compile SQLite with
SQLITE_THREADSAFE=1.  Ticket #2588. (CVS 4297)

FossilOrigin-Name: 1668284d151e78d16b0d83bf55dfd9d349a452a7

manifest

@@ -1,5 +1,5 @@
-C Update\sthe\srest\sof\sthe\smalloc\sfailure\stest\sscripts\sto\suse\sthe\snew\sinterface.\s(CVS\s4296)
-D 2007-08-25T13:37:49
+C Use\srecursive\smutexes\sin\spthreads.\s\sIf\sthe\spthreads\simplementation\sdoes\snot\nsupport\srecursive\smutexes,\sthen\syou\scannot\scompile\sSQLite\swith\nSQLITE_THREADSAFE=1.\s\sTicket\s#2588.\s(CVS\s4297)
+D 2007-08-25T14:39:46
 F Makefile.in 938f2769921fa1b30c633548f153804021eb1512
 F Makefile.linux-gcc 65241babba6faf1152bf86574477baab19190499
 F README 9c4e2d6706bdcc3efdd773ce752a8cdab4f90028
@@ -103,7 +103,7 @@ F src/malloc.c d4282f50964ab1ca31f504c97b7cf2fdb4d4195d
 F src/md5.c c5fdfa5c2593eaee2e32a5ce6c6927c986eaf217
 F src/mem1.c afe2fbf6d7e8247c6c9f69c1481358b1cad60c08
 F src/mem2.c 1a2ca756a285b5365d667841508cc1f98938b8d8
-F src/mutex.c 2337e3105ee274be77b743e43ffb053a1bca89e2
+F src/mutex.c 81e4c57389ba5851b6bc78c704508f0a1d8659b8
 F src/os.c a8ed3c495161475dbce255f7003144144fb425f1
 F src/os.h 2bfbbad126a775e4d8c7d59eb4d9585a5fd7dfb5
 F src/os_common.h a5c446d3b93f09f369d13bf217de4bed3437dd1c
@@ -127,7 +127,7 @@ F src/server.c 087b92a39d883e3fa113cae259d64e4c7438bc96
 F src/shell.c ac29402b538515fa4697282387be9c1205e6e9eb
 F src/sqlite.h.in 22397464e1026437a755489c3eeb459346ae8749
 F src/sqlite3ext.h 9a26028378c288af500d8b94ed079666fed5806b
-F src/sqliteInt.h ea7a14a33c0a03479d2d98ce9ac83fe5e7f4bb55
+F src/sqliteInt.h 13c908f5f156a192fcd247f993ac513bfaf81f53
 F src/sqliteLimit.h 1bcbbdfa856f8b71b561abb31edb864b0eca1d12
 F src/table.c c725e47f6f3092b9a7b569fc58e408e2173ee008
 F src/tclsqlite.c d76af53f45c9e9f7f7d39531fa4c7bee7d0adad6
@@ -561,7 +561,7 @@ F www/tclsqlite.tcl 8be95ee6dba05eabcd27a9d91331c803f2ce2130
 F www/vdbe.tcl 87a31ace769f20d3627a64fa1fade7fed47b90d0
 F www/version3.tcl 890248cf7b70e60c383b0e84d77d5132b3ead42b
 F www/whentouse.tcl fc46eae081251c3c181bd79c5faef8195d7991a5
-P e5ec17071720a973bbd213a8b23038d3aff25315
-R a2a459ce4d89b3260dd62868dc774bc5
-U danielk1977
-Z 07d9ea0b58d791968ed1c4e04f1541a3
+P b076e1655d6bae5ae10e6ceee646f502435da66a
+R edf973d5cbe24872437fb8ece94bf656
+U drh
+Z efa71bea2fd6dc4b3f3ab38d3c01a446

manifest.uuid

@@ -1 +1 @@
-b076e1655d6bae5ae10e6ceee646f502435da66a
+1668284d151e78d16b0d83bf55dfd9d349a452a7

src/mutex.c

@@ -12,7 +12,7 @@
 ** This file contains the C functions that implement mutexes for
 ** use by the SQLite core.
 **
-** $Id: mutex.c,v 1.10 2007/08/25 03:59:09 drh Exp $
+** $Id: mutex.c,v 1.11 2007/08/25 14:39:46 drh Exp $
 */
 /*
 ** If SQLITE_MUTEX_APPDEF is defined, then this whole module is
@@ -208,10 +208,10 @@ int sqlite3_mutex_notheld(sqlite3_mutex *p){
 
 
 #ifdef SQLITE_MUTEX_PTHREAD
-/**************** Non-recursive Pthread Mutex Implementation *****************
+/******************** Pthread Mutex Implementation *********************
 **
 ** This implementation of mutexes is built using a version of pthreads that
-** does not have native support for recursive mutexes.
+** has native support for recursive mutexes.
 */
 #include <pthread.h>
 
@@ -274,8 +274,27 @@ sqlite3_mutex *sqlite3_mutex_alloc(int iType){
   };
   sqlite3_mutex *p;
   switch( iType ){
-    case SQLITE_MUTEX_FAST:
     case SQLITE_MUTEX_RECURSIVE: {
+      static pthread_mutex_t initMutex = PTHREAD_MUTEX_INITIALIZER;
+      static int isInit = 0;
+      static pthread_mutexattr_t recursiveAttr;
+      if( !isInit ){
+        pthread_mutex_lock(&initMutex);
+        if( !isInit ){
+          pthread_mutexattr_init(&recursiveAttr);
+          pthread_mutexattr_settype(&recursiveAttr, PTHREAD_MUTEX_RECURSIVE);
+        }
+        isInit = 1;
+        pthread_mutex_unlock(&initMutex);
+      }
+      p = sqlite3MallocZero( sizeof(*p) );
+      if( p ){
+        p->id = iType;
+        pthread_mutex_init(&p->mutex, &recursiveAttr);
+      }
+      break;
+    }
+    case SQLITE_MUTEX_FAST: {
       p = sqlite3MallocZero( sizeof(*p) );
       if( p ){
         p->id = iType;
@@ -320,27 +339,20 @@ void sqlite3_mutex_free(sqlite3_mutex *p){
 ** more than once, the behavior is undefined.
 */
 void sqlite3_mutex_enter(sqlite3_mutex *p){
-  pthread_t self = pthread_self();
-  if( p->nRef>0 && pthread_equal(p->owner, self) ){
-    p->nRef++;
-  }else{
-    pthread_mutex_lock(&p->mutex);
-    assert( p->nRef==0 );
-    p->owner = self;
-    p->nRef = 1;
-  }
+  assert( p );
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
+  pthread_mutex_lock(&p->mutex);
+  p->owner = pthread_self();
+  p->nRef++;
 }
 int sqlite3_mutex_try(sqlite3_mutex *p){
-  pthread_t self = pthread_self();
   int rc;
-  if( p->nRef>0 && pthread_equal(p->owner, self) ){
+  assert( p );
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
+  if( pthread_mutex_trylock(&p->mutex)==0 ){
+    p->owner = pthread_self();
     p->nRef++;
     rc = SQLITE_OK;
-  }else if( pthread_mutex_lock(&p->mutex)==0 ){
-    assert( p->nRef==0 );
-    p->owner = self;
-    p->nRef = 1;
-    rc = SQLITE_OK;
   }else{
     rc = SQLITE_BUSY;
   }
@@ -354,12 +366,10 @@ int sqlite3_mutex_try(sqlite3_mutex *p){
 ** is not currently allocated.  SQLite will never do either.
 */
 void sqlite3_mutex_leave(sqlite3_mutex *p){
-  assert( pthread_equal(p->owner, pthread_self()) );
-  assert( p->nRef>0 );
+  assert( p );
+  assert( sqlite3_mutex_held(p) );
   p->nRef--;
-  if( p->nRef==0 ){
-    pthread_mutex_unlock(&p->mutex);
-  }
+  pthread_mutex_unlock(&p->mutex);
 }
 
 /*
@@ -493,12 +503,16 @@ void sqlite3_mutex_free(sqlite3_mutex *p){
 ** more than once, the behavior is undefined.
 */
 void sqlite3_mutex_enter(sqlite3_mutex *p){
+  assert( p );
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
   EnterCriticalSection(&p->mutex);
   p->owner = GetCurrentThreadId(); 
   p->nRef++;
 }
 int sqlite3_mutex_try(sqlite3_mutex *p){
   int rc;
+  assert( p );
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
   if( TryEnterCriticalSection(&p->mutex) ){
     p->owner = GetCurrentThreadId();
     p->nRef++;

src/sqliteInt.h

@@ -11,12 +11,13 @@
 *************************************************************************
 ** Internal interface definitions for SQLite.
 **
-** @(#) $Id: sqliteInt.h,v 1.599 2007/08/24 08:15:54 danielk1977 Exp $
+** @(#) $Id: sqliteInt.h,v 1.600 2007/08/25 14:39:46 drh Exp $
 */
 #ifndef _SQLITEINT_H_
 #define _SQLITEINT_H_
 #include "sqliteLimit.h"
 
+#define _XOPEN_SOURCE 500  /* Needed to enable pthread recursive mutexes */
 
 #if defined(SQLITE_TCL) || defined(TCLSH)
 # include <tcl.h>