Fix a threads/mutex problem in pcache.c. (CVS 5630)

FossilOrigin-Name: 1928f15b78eee0fbf0a8ecdbbdd38dbbde2942b8

manifest

@@ -1,5 +1,5 @@
-C Miscellaneous\scleanup\sin\sthe\snew\spcache\scode.\s(CVS\s5629)
+C Fix\sa\sthreads/mutex\sproblem\sin\spcache.c.\s(CVS\s5630)
-D 2008-08-28T02:26:07
+D 2008-08-28T08:31:48
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in 689e14735f862a5553bceef206d8c13e29504e44
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -137,7 +137,7 @@ F src/os_win.c aefe9ee26430678a19a058a874e4e2bd91398142
 F src/pager.c 032d11049af4ec49bdbaa3584e7ce9887098b66a
 F src/pager.h 914103bb62dbcc3d8e9f14baec812d027264d457
 F src/parse.y d0f76d2cb8d6883d5600dc20beb961a6022b94b8
-F src/pcache.c aa609c9b1fc1a2b00f7d7bfb3d06b1e507767b93
+F src/pcache.c 8a2d92fb12ede40cfc8532f062763f353ba2868a
 F src/pcache.h bd373ee3e4db310d6bbe7fa6d8d971de9678edd8
 F src/pragma.c f5b271b090af7fcedd308d7c5807a5503f7a853d
 F src/prepare.c c197041e0c4770672cda75e6bfe10242f885e510
@@ -450,7 +450,7 @@ F test/pragma2.test 5364893491b9231dd170e3459bfc2e2342658b47
 F test/printf.test 262a5acd3158f788e9bdf7f18d718f3af32ff6ef
 F test/progress.test 5b075c3c790c7b2a61419bc199db87aaf48b8301 x
 F test/ptrchng.test ef1aa72d6cf35a2bbd0869a649b744e9d84977fc
-F test/quick.test 4e702221947cf31a624f929502e55871bcb11dbc
+F test/quick.test ab9399a71983f67113c04bab331edb59b950e2d6
 F test/quote.test 215897dbe8de1a6f701265836d6601cc6ed103e6
 F test/rdonly.test bd054831f8a3078e765a0657e247182486f0cb47
 F test/reindex.test 44edd3966b474468b823d481eafef0c305022254
@@ -503,6 +503,7 @@ F test/temptable.test 19b851b9e3e64d91e9867619b2a3f5fffee6e125
 F test/tester.tcl 12fd8394caeb71f7d961707da8668756389bc9d3
 F test/thread001.test 3fb08080e1fe84d1bb7ec7bbc9e13743a77e5bc5
 F test/thread002.test ed9b800460df01e3cf9428ee11dc4e3f04b9b896
+F test/thread003.test 6e612660f31c49f70bbe2e6c78af1eed54d89968
 F test/thread1.test 776c9e459b75ba905193b351926ac4019b049f35
 F test/thread2.test 6d7b30102d600f51b4055ee3a5a19228799049fb
 F test/thread_common.tcl 8a9d7a4500dfdbbd36679c977831b62c130b76b1
@@ -624,7 +625,7 @@ F tool/speedtest16.c c8a9c793df96db7e4933f0852abb7a03d48f2e81
 F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 1dbced29de5f59ba2ebf877edcadf171540374d1
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
-P ce9c74eaab459ddde213c828e821940f5d6cb354
+P da1777259f53c2e20c7ced06bf6f2a550f0ea0fc
-R 55c280ec697a3a6039a240cf488ad9ad
+R 825acac92c02335d51391b9bead07be1
-U drh
+U danielk1977
-Z 7df830e688305e6be422e59df78b53fe
+Z ccfb17e90f1b78b85072c08441535cfa

manifest.uuid

@@ -1 +1 @@
-da1777259f53c2e20c7ced06bf6f2a550f0ea0fc
+1928f15b78eee0fbf0a8ecdbbdd38dbbde2942b8

src/pcache.c

@@ -11,7 +11,7 @@
 *************************************************************************
 ** This file implements that page cache.
 **
-** @(#) $Id: pcache.c,v 1.19 2008/08/28 02:26:07 drh Exp $
+** @(#) $Id: pcache.c,v 1.20 2008/08/28 08:31:48 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 
@@ -685,22 +685,23 @@ int sqlite3PcacheFetch(
   /* Search the hash table for the requested page. Exit early if it is found. */
   if( pCache->apHash ){
     u32 h = pgno % pCache->nHash;
+    pcacheEnterMutex();
     for(pPage=pCache->apHash[h]; pPage; pPage=pPage->pNextHash){
       if( pPage->pgno==pgno ){
         if( pPage->nRef==0 ){
           if( 0==(pPage->flags&PGHDR_DIRTY) ){
-            pcacheEnterMutex();
             pcacheRemoveFromLruList(pPage);
-            pcacheExitMutex();
             pCache->nPinned++;
           }
           pCache->nRef++;
         }
         pPage->nRef++;
         *ppPage = pPage;
+        pcacheExitMutex();
         return SQLITE_OK;
       }
     }
+    pcacheExitMutex();
   }
 
   if( createFlag ){

test/quick.test

@@ -6,7 +6,7 @@
 #***********************************************************************
 # This file runs all tests.
 #
-# $Id: quick.test,v 1.85 2008/08/27 18:56:36 drh Exp $
+# $Id: quick.test,v 1.86 2008/08/28 08:31:48 danielk1977 Exp $
 
 proc lshift {lvar} {
   upvar $lvar l
@@ -76,6 +76,7 @@ set EXCLUDE {
   tkt2686.test
   thread001.test
   thread002.test
+  thread003.test
   trans2.test
   vacuum3.test
 

test/thread003.test

@@ -0,0 +1,115 @@
+# 2007 September 10
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+#   This file contains tests that attempt to break the pcache module
+#   by bombarding it with simultaneous requests from multiple threads.
+#     
+# $Id: thread003.test,v 1.1 2008/08/28 08:31:48 danielk1977 Exp $
+
+set testdir [file dirname $argv0]
+
+source $testdir/tester.tcl
+source $testdir/thread_common.tcl
+if {[info commands sqlthread] eq ""} {
+  finish_test
+  return
+}
+
+# Set up a couple of different databases full of pseudo-randomly 
+# generated data.
+#
+do_test thread003.1.1 {
+  execsql {
+    BEGIN;
+    CREATE TABLE t1(a, b, c);
+  }
+  for {set ii 0} {$ii < 5000} {incr ii} {
+    execsql {INSERT INTO t1 VALUES($ii, randomblob(200), randomblob(200))}
+  }
+  execsql { 
+    CREATE INDEX i1 ON t1(a, b); 
+    COMMIT;
+  }
+} {}
+do_test thread003.1.2 {
+  expr {([file size test.db] / 1024) > 2000}
+} {1}
+do_test thread003.1.3 {
+  db close
+  file delete -force test2.db
+  sqlite3 db test2.db
+} {}
+do_test thread003.1.4 {
+  execsql {
+    BEGIN;
+    CREATE TABLE t1(a, b, c);
+  }
+  for {set ii 0} {$ii < 5000} {incr ii} {
+    execsql {INSERT INTO t1 VALUES($ii, randomblob(200), randomblob(200))}
+  }
+  execsql { 
+    CREATE INDEX i1 ON t1(a, b); 
+    COMMIT;
+  }
+} {}
+do_test thread003.1.5 {
+  expr {([file size test.db] / 1024) > 2000}
+} {1}
+do_test thread003.1.6 {
+  db close
+} {}
+
+
+# This test opens a connection on each of the large (>2MB) database files
+# created by the previous block. The connections do not share a cache.
+# Both "cache_size" parameters are set to 15, so there is a maximum of
+# 30 pages available globally.
+#
+# Then, in separate threads, the databases are randomly queried over and
+# over again. This will force the connections to recycle clean pages from
+# each other. If there is a thread-safety problem, a segfault or assertion
+# failure may eventually occur.
+#
+set nSecond 30
+puts "Starting thread003.2 (should run for ~$nSecond seconds)"
+do_test thread003.2 {
+  foreach zFile {test.db test2.db} {
+    set SCRIPT [format {
+      set iStart [clock seconds]
+      set iEnd [expr {[clock seconds] + %d}]
+      set ::DB [sqlthread open %s]
+  
+      # Set the cache size to 15 pages per cache. 30 available globally.
+      execsql { PRAGMA cache_size = 15 }
+  
+      while {[clock seconds] < $iEnd} {
+        set iQuery [expr {int(rand()*5000)}]
+        execsql " SELECT * FROM t1 WHERE a = $iQuery "
+      }
+  
+      sqlite3_close $::DB
+      expr 1
+    } $nSecond $zFile]
+  
+    unset -nocomplain finished($zFile)
+    thread_spawn finished($zFile) $thread_procs $SCRIPT
+  }
+  foreach zFile {test.db test2.db} {
+    if {![info exists finished($zFile)]} {
+      vwait finished($zFile)
+    }
+  }
+  expr 0
+} {0}
+
+finish_test
+
+