diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/os_unix.c | 13 | ||||
| -rw-r--r-- | src/wal.c | 63 |
2 files changed, 57 insertions, 19 deletions
diff --git a/src/os_unix.c b/src/os_unix.c index dab03c97f..7362a1320 100644 --- a/src/os_unix.c +++ b/src/os_unix.c @@ -4595,7 +4595,20 @@ static int unixLockSharedMemory(unixFile *pDbFd, unixShmNode *pShmNode){ pShmNode->isUnlocked = 1; rc = SQLITE_READONLY_CANTINIT; }else{ +#ifdef SQLITE_ENABLE_SETLK_TIMEOUT + /* Do not use a blocking lock here. If the lock cannot be obtained + ** immediately, it means some other connection is truncating the + ** *-shm file. And after it has done so, it will not release its + ** lock, but only downgrade it to a shared lock. So no point in + ** blocking here. The call below to obtain the shared DMS lock may + ** use a blocking lock. */ + int iSaveTimeout = pDbFd->iBusyTimeout; + pDbFd->iBusyTimeout = 0; +#endif rc = unixShmSystemLock(pDbFd, F_WRLCK, UNIX_SHM_DMS, 1); +#ifdef SQLITE_ENABLE_SETLK_TIMEOUT + pDbFd->iBusyTimeout = iSaveTimeout; +#endif /* The first connection to attach must truncate the -shm file. We ** truncate to 3 bytes (an arbitrary small number, less than the ** -shm header size) rather than 0 as a system debugging aid, to @@ -2004,6 +2004,19 @@ static int walIteratorInit(Wal *pWal, u32 nBackfill, WalIterator **pp){ } #ifdef SQLITE_ENABLE_SETLK_TIMEOUT + + +/* +** Attempt to enable blocking locks that block for nMs ms. Return 1 if +** blocking locks are successfully enabled, or 0 otherwise. +*/ +static int walEnableBlockingMs(Wal *pWal, int nMs){ + int rc = sqlite3OsFileControl( + pWal->pDbFd, SQLITE_FCNTL_LOCK_TIMEOUT, (void*)&nMs + ); + return (rc==SQLITE_OK); +} + /* ** Attempt to enable blocking locks. Blocking locks are enabled only if (a) ** they are supported by the VFS, and (b) the database handle is configured @@ -2015,11 +2028,7 @@ static int walEnableBlocking(Wal *pWal){ if( pWal->db ){ int tmout = pWal->db->busyTimeout; if( tmout ){ - int rc; - rc = sqlite3OsFileControl( - pWal->pDbFd, SQLITE_FCNTL_LOCK_TIMEOUT, (void*)&tmout - ); - res = (rc==SQLITE_OK); + res = walEnableBlockingMs(pWal, tmout); } } return res; @@ -2068,20 +2077,10 @@ void sqlite3WalDb(Wal *pWal, sqlite3 *db){ pWal->db = db; } -/* -** Take an exclusive WRITE lock. Blocking if so configured. -*/ -static int walLockWriter(Wal *pWal){ - int rc; - walEnableBlocking(pWal); - rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1); - walDisableBlocking(pWal); - return rc; -} #else # define walEnableBlocking(x) 0 # define walDisableBlocking(x) -# define walLockWriter(pWal) walLockExclusive((pWal), WAL_WRITE_LOCK, 1) +# define walEnableBlockingMs(pWal, ms) 0 # define sqlite3WalDb(pWal, db) #endif /* ifdef SQLITE_ENABLE_SETLK_TIMEOUT */ @@ -2682,7 +2681,9 @@ static int walIndexReadHdr(Wal *pWal, int *pChanged){ } }else{ int bWriteLock = pWal->writeLock; - if( bWriteLock || SQLITE_OK==(rc = walLockWriter(pWal)) ){ + if( bWriteLock + || SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1)) + ){ pWal->writeLock = 1; if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){ badHdr = walIndexTryHdr(pWal, pChanged); @@ -2690,7 +2691,8 @@ static int walIndexReadHdr(Wal *pWal, int *pChanged){ /* If the wal-index header is still malformed even while holding ** a WRITE lock, it can only mean that the header is corrupted and ** needs to be reconstructed. So run recovery to do exactly that. - */ + ** Disable blocking locks first. */ + walDisableBlocking(pWal); rc = walIndexRecover(pWal); *pChanged = 1; } @@ -2957,6 +2959,9 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){ int i; /* Loop counter */ int rc = SQLITE_OK; /* Return code */ u32 mxFrame; /* Wal frame to lock to */ +#ifdef SQLITE_ENABLE_SETLK_TIMEOUT + int nBlockTmout = 0; +#endif assert( pWal->readLock<0 ); /* Not currently locked */ @@ -2987,6 +2992,19 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){ return SQLITE_PROTOCOL; } if( cnt>=10 ) nDelay = (cnt-9)*(cnt-9)*39; +#ifdef SQLITE_ENABLE_SETLK_TIMEOUT + /* In SQLITE_ENABLE_SETLK_TIMEOUT builds, configure the file-descriptor + ** to block for locks for approximately nDelay us. This affects three + ** locks: (a) the shared lock taken on the DMS slot in os_unix.c (if + ** using os_unix.c), (b) the WRITER lock taken in walIndexReadHdr() if the + ** first attempted read fails, and (c) the shared lock taken on the DMS + ** slot in os_unix.c. All three of these locks are attempted from within + ** the call to walIndexReadHdr() below. */ + nBlockTmout = (nDelay+998) / 1000; + if( !useWal && walEnableBlockingMs(pWal, nBlockTmout) ){ + nDelay = 1; + } +#endif sqlite3OsSleep(pWal->pVfs, nDelay); } @@ -2995,6 +3013,10 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){ if( pWal->bShmUnreliable==0 ){ rc = walIndexReadHdr(pWal, pChanged); } +#ifdef SQLITE_ENABLE_SETLK_TIMEOUT + walDisableBlocking(pWal); + if( rc==SQLITE_BUSY_TIMEOUT ) rc = SQLITE_BUSY; +#endif if( rc==SQLITE_BUSY ){ /* If there is not a recovery running in another thread or process ** then convert BUSY errors to WAL_RETRY. If recovery is known to @@ -3109,9 +3131,12 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){ return rc==SQLITE_BUSY ? WAL_RETRY : SQLITE_READONLY_CANTINIT; } + (void)walEnableBlockingMs(pWal, nBlockTmout); rc = walLockShared(pWal, WAL_READ_LOCK(mxI)); + walDisableBlocking(pWal); if( rc ){ - return rc==SQLITE_BUSY ? WAL_RETRY : rc; + assert( (rc&0xFF)!=SQLITE_BUSY||rc==SQLITE_BUSY||rc==SQLITE_BUSY_TIMEOUT ); + return (rc&0xFF)==SQLITE_BUSY ? WAL_RETRY : rc; } /* Now that the read-lock has been obtained, check that neither the ** value in the aReadMark[] array or the contents of the wal-index |