mirror of
https://github.com/sqlite/sqlite.git
synced 2025-08-07 02:42:48 +03:00
Block on the WRITER lock when attempting to run recovery.
FossilOrigin-Name: 105d6c9bbcadc64faa2b24e315cb13227b17cfc6bf1b3512713f80ce56976a3d
This commit is contained in:
dan
163
src/wal.c
163
src/wal.c
@@ -466,9 +466,9 @@ struct Wal {
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#endif
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#ifdef SQLITE_ENABLE_SNAPSHOT
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WalIndexHdr *pSnapshot; /* Start transaction here if not NULL */
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# ifdef SQLITE_ENABLE_SETLK_TIMEOUT
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sqlite3 *dbSnapshot;
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# endif
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#endif
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#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
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sqlite3 *db;
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#endif
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};
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@@ -2118,6 +2118,88 @@ static int walIndexTryHdr(Wal *pWal, int *pChanged){
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*/
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#define WAL_RETRY (-1)
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#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
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/*
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** Attempt to enable blocking locks. Blocking locks are enabled only if (a)
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** they are supported by the VFS, and (b) the database handle is configured
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** with a busy-timeout. Return 1 if blocking locks are successfully enabled,
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** or 0 otherwise.
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*/
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static int walEnableBlocking(Wal *pWal){
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int res = 0;
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if( pWal->db ){
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int tmout = pWal->db->busyTimeout;
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if( tmout ){
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int rc;
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rc = sqlite3OsFileControl(
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pWal->pDbFd, SQLITE_FCNTL_LOCK_TIMEOUT, (void*)&tmout
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);
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res = (rc==SQLITE_OK);
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}
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}
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return res;
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}
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/*
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** Disable blocking locks.
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*/
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static void walDisableBlocking(Wal *pWal){
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int tmout = 0;
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sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_LOCK_TIMEOUT, (void*)&tmout);
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}
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/*
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** If parameter bLock is true, attempt to enable blocking locks, take
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** the WRITER lock, and then disable blocking locks. If blocking locks
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** cannot be enabled, no attempt to obtain the WRITER lock is made. Return
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** an SQLite error code if an error occurs, or SQLITE_OK otherwise. It is not
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** an error if blocking locks can not be enabled.
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**
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** If the bLock parameter is false and the WRITER lock is held, release it.
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*/
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int sqlite3WalWriteLock(Wal *pWal, int bLock){
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int rc = SQLITE_OK;
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assert( pWal->readLock<0 || bLock==0 );
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if( bLock ){
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assert( pWal->db );
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if( walEnableBlocking(pWal) ){
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rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1);
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if( rc==SQLITE_OK ){
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pWal->writeLock = 1;
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}
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walDisableBlocking(pWal);
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}
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}else if( pWal->writeLock ){
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walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
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pWal->writeLock = 0;
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}
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return rc;
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}
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/*
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** Set the database handle used to determine if blocking locks are required.
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*/
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void sqlite3WalDb(Wal *pWal, sqlite3 *db){
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pWal->db = db;
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}
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/*
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** Take an exclusive WRITE lock. Blocking if so configured.
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*/
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static int walLockWriter(Wal *pWal){
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int rc;
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walEnableBlocking(pWal);
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rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1);
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walDisableBlocking(pWal);
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return rc;
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}
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#else
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# define walEnableBlocking(x) 0
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# define walDisableBlocking(x)
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# define walLockWriter(pWal) walLockExclusive((pWal), WAL_WRITE_LOCK, 1)
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# define sqlite3WalDb(pWal)
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#endif /* ifdef SQLITE_ENABLE_SETLK_TIMEOUT */
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/*
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** Read the wal-index header from the wal-index and into pWal->hdr.
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** If the wal-header appears to be corrupt, try to reconstruct the
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@@ -2183,9 +2265,7 @@ static int walIndexReadHdr(Wal *pWal, int *pChanged){
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}
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}else{
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int bWriteLock = pWal->writeLock;
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if( bWriteLock
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|| SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1))
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){
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if( bWriteLock || SQLITE_OK==(rc = walLockWriter(pWal)) ){
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pWal->writeLock = 1;
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if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){
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badHdr = walIndexTryHdr(pWal, pChanged);
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@@ -2737,65 +2817,6 @@ int sqlite3WalSnapshotRecover(Wal *pWal){
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}
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#endif /* SQLITE_ENABLE_SNAPSHOT */
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#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
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/*
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** Attempt to enable blocking locks. Blocking locks are enabled only if (a)
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** they are supported by the VFS, and (b) the database handle is configured
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** with a busy-timeout. Return 1 if blocking locks are successfully enabled,
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** or 0 otherwise.
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*/
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static int walEnableBlocking(sqlite3 *db, Wal *pWal){
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int res = 0;
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if( db->busyTimeout ){
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int rc;
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int tmout = db->busyTimeout;
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rc = sqlite3OsFileControl(
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pWal->pDbFd, SQLITE_FCNTL_LOCK_TIMEOUT, (void*)&tmout
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);
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res = (rc==SQLITE_OK);
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}
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return res;
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}
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/*
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** Disable blocking locks.
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*/
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static void walDisableBlocking(Wal *pWal){
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int tmout = 0;
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sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_LOCK_TIMEOUT, (void*)&tmout);
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}
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/*
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** If parameter bLock is true, attempt to enable blocking locks, take
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** the WRITER lock, and then disable blocking locks. If blocking locks
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** cannot be enabled, no attempt to obtain the WRITER lock is made. Return
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** an SQLite error code if an error occurs, or SQLITE_OK otherwise. It is not
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** an error if blocking locks can not be enabled.
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**
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** If the bLock parameter is false and the WRITER lock is held, release it.
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*/
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int sqlite3WalWriteLock(sqlite3 *db, Wal *pWal, int bLock){
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int rc = SQLITE_OK;
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assert( pWal->readLock<0 || bLock==0 );
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if( bLock ){
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if( walEnableBlocking(db, pWal) ){
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rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1);
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if( rc==SQLITE_OK ){
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pWal->writeLock = 1;
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}
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walDisableBlocking(pWal);
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}
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}else if( pWal->writeLock ){
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walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
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pWal->writeLock = 0;
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}
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return rc;
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}
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#else
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# define walEnableBlocking(x,y) 0
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# define walDisableBlocking(x)
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#endif /* ifdef SQLITE_ENABLE_SETLK_TIMEOUT */
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/*
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** Begin a read transaction on the database.
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**
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@@ -2832,7 +2853,7 @@ int sqlite3WalBeginReadTransaction(Wal *pWal, int *pChanged){
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** its intent. To avoid the race condition this leads to, ensure that
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** there is no checkpointer process by taking a shared CKPT lock
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** before checking pInfo->nBackfillAttempted. */
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walEnableBlocking(pWal->dbSnapshot, pWal);
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walEnableBlocking(pWal);
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rc = walLockShared(pWal, WAL_CKPT_LOCK);
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walDisableBlocking(pWal);
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@@ -3666,7 +3687,8 @@ int sqlite3WalCheckpoint(
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/* Enable blocking locks, if possible. If blocking locks are successfully
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** enabled, set xBusy2=0 so that the busy-handler is never invoked. */
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if( walEnableBlocking(db, pWal) ){
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sqlite3WalDb(pWal, db);
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if( walEnableBlocking(pWal) ){
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xBusy2 = 0;
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}
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@@ -3710,7 +3732,7 @@ int sqlite3WalCheckpoint(
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if( rc==SQLITE_OK ){
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walDisableBlocking(pWal);
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rc = walIndexReadHdr(pWal, &isChanged);
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walEnableBlocking(db, pWal);
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walEnableBlocking(pWal);
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if( isChanged && pWal->pDbFd->pMethods->iVersion>=3 ){
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sqlite3OsUnfetch(pWal->pDbFd, 0, 0);
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}
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@@ -3743,6 +3765,7 @@ int sqlite3WalCheckpoint(
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}
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walDisableBlocking(pWal);
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sqlite3WalDb(pWal, 0);
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/* Release the locks. */
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sqlite3WalEndWriteTransaction(pWal);
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@@ -3869,13 +3892,9 @@ int sqlite3WalSnapshotGet(Wal *pWal, sqlite3_snapshot **ppSnapshot){
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*/
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void sqlite3WalSnapshotOpen(
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Wal *pWal,
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sqlite3 *db,
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sqlite3_snapshot *pSnapshot
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){
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pWal->pSnapshot = (WalIndexHdr*)pSnapshot;
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#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
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pWal->dbSnapshot = db;
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#endif
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}
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/*
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