Revert [SQLite] Hack to touch page cache to debug slow connection close.

Original CL http://codereview.chromium.org/7891025 , http://crrev.com/101034

The hypothesis discussed in that CL seems proven out, as the
shutdown-hang crashes mostly moved from sqlite3_close() into
sqlite3_95527().

BUG=95527
TEST=Monitor crash in bug, see if it changes.


Review URL: https://chromiumcodereview.appspot.com/9845034

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@137989 0039d316-1c4b-4281-b951-d872f2087c98

sql/connection.cc

@@ -125,21 +125,6 @@ void Connection::Close() {
   ClearCache();
 
   if (db_) {
-    // TODO(shess): Some additional code to debug http://crbug.com/95527 .
-    // If you are reading this due to link errors or something, it can
-    // be safely removed.
-#if defined(HAS_SQLITE3_95527)
-    unsigned int nTouched = 0;
-    sqlite3_95527(db_, &nTouched);
-
-    // If a VERY large amount of memory was touched, crash.  This
-    // should never happen.
-    // TODO(shess): Pull this in.  It should be page_size * page_cache
-    // or something like that, 4M or 16M.  For now it's just to
-    // prevent optimization.
-    CHECK_LT(nTouched, 1000*1000*1000U);
-#endif
-
     // TODO(shess): Histogram for failure.
     sqlite3_close(db_);
     db_ = NULL;

third_party/sqlite/amalgamation/sqlite3.c

@@ -126259,94 +126259,3 @@ SQLITE_PRIVATE void sqlite3Fts3IcuTokenizerModule(
 #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
 
 /************** End of fts3_icu.c ********************************************/
-
-/* Touch the bigs of pCache which will be processed by
-** pcache1TruncateUnsafe(), pcache1FreePage(), and pcache1Free()
-** during sqlite3_close().  *pnTouched will have the number of bytes
-** represented by the pages touched added to it. */
-SQLITE_PRIVATE void pcache1VisitUnsafe(PCache1 *pCache,
-                                       unsigned int *pnTouched){
-  unsigned int iHash;
-
-  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
-
-  for(iHash=0; iHash<pCache->nHash; iHash++){
-    PgHdr1 *pp = pCache->apHash[iHash];
-    PgHdr1 *lp = pp;
-    unsigned int s = 0;
-    while (pp) {
-      /* Crash if a loop is detected. */
-      /* NOTE(shess): Touches the PgHdr1 structure as a side effect.
-      ** If this check is removed, revise the code to match ordering
-      ** in pcache1TruncateUnsafe().  Yes, I realize this is
-      ** probably reordered to heck and back.
-      */
-      if (lp == pp->pNext) {
-        int *zero = NULL;
-        *zero = 42;
-      }
-
-      /* Touch the data area, in case it's on a prior VM page. */
-      *pnTouched += sqlite3MallocSize(PGHDR1_TO_PAGE(pp));
-
-      pp = pp->pNext;
-
-      /* Bump the loop-detection pointer forward every time s is an
-      ** even power of 2. */
-      s++;
-      if (!(s & (s-1))) {
-        lp = pp;
-      }
-    }
-  }
-}
-
-/* TODO(shess): Debugging code for http://crbug.com/95527 .
-** Touch the entire page cache for the given db.  The idea is that if
-** paging activity is causing the slowdown, the shutdown monitor will
-** see things happening here, rather than in sqlite3_close().
-*/
-int sqlite3_95527(sqlite3 *db, unsigned int *pnTouched){
-  unsigned int iDb;
-
-  /* This code assumes that pcache1 is the pager cache implementation. */
-  if (sqlite3GlobalConfig.pcache.xTruncate != pcache1Truncate) {
-    return SQLITE_OK;
-  }
-
-  /* This setup is like sqlite3_close(). */
-  if( !db ){
-    return SQLITE_OK;
-  }
-  if( !sqlite3SafetyCheckSickOrOk(db) ){
-    return SQLITE_MISUSE_BKPT;
-  }
-  sqlite3_mutex_enter(db->mutex);
-
-  /* A sqlite3* connection may refer to multiple underlying database
-     files.  Usually these will be 'main' and 'temp', with 'temp' having
-     no btree or pager. */
-  for(iDb=0; iDb<db->nDb; iDb++){
-    Btree *b;
-    Pager *p;
-    PCache1 *pCache;
-    struct Db *pDb = &db->aDb[iDb];
-    if (!pDb) continue;
-
-    b = pDb->pBt;
-    if (!b) continue;
-
-    p = sqlite3BtreePager(b);
-    if (!p) continue;
-
-    pCache = (PCache1*)p->pPCache->pCache;
-    if (!pCache) continue;
-
-    pcache1EnterMutex(pCache->pGroup);
-    pcache1VisitUnsafe(pCache, pnTouched);
-    pcache1LeaveMutex(pCache->pGroup);
-  }
-
-  sqlite3_mutex_leave(db->mutex);
-  return SQLITE_OK;
-}

third_party/sqlite/amalgamation/sqlite3.h

@@ -6477,18 +6477,3 @@ struct sqlite3_rtree_geometry {
 
 #endif  /* ifndef _SQLITE3RTREE_H_ */
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-/* Fault in page cache for db.  See http://crbug.com/95527 .
-** *pnTouched will accumulate the number of bytes represented by the
-** touched pages. */
-int sqlite3_95527(sqlite3 *db, unsigned int *pnTouched);
-
-/* Let our code know that it's safe to call the function. */
-#define HAS_SQLITE3_95527
-
-#ifdef __cplusplus
-}  /* end of the 'extern "C"' block */
-#endif