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In SQLITE_ENABLE_SETLK_TIMEOUT builds, use blocking locks in place of sleep() calls when opening a read-transaction.

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FossilOrigin-Name: 4c055b7a6e4533e1e571773456226ca7038ce372df3eedbbbcd9a81e8652a6cf
This commit is contained in:
dan
2023-11-28 17:12:42 +00:00
parent 48cca2422e b8950e0f45
commit 940b23bc3a
4 changed files with 66 additions and 27 deletions
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63
src/wal.c
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@@ -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