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Arrange for some of the transient locks in WAL mode to block, as a single

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to the OS to fix priority inversions.

FossilOrigin-Name: c6e6d5f4e06c3ac0bfb620c0c728fbc7230c4a02
This commit is contained in:
drh
2015-03-10 20:22:35 +00:00
parent 94929646f1
commit bbf76eec34
5 changed files with 48 additions and 26 deletions
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17
src/wal.c
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@@ -788,9 +788,10 @@ static void walUnlockShared(Wal *pWal, int lockIdx){
SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED);
WALTRACE(("WAL%p: release SHARED-%s\n", pWal, walLockName(lockIdx)));
}
static int walLockExclusive(Wal *pWal, int lockIdx, int n){
static int walLockExclusive(Wal *pWal, int lockIdx, int n, int fBlock){
int rc;
if( pWal->exclusiveMode ) return SQLITE_OK;
if( fBlock ) sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_WAL_BLOCK, 0);
rc = sqlite3OsShmLock(pWal->pDbFd, lockIdx, n,
SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE);
WALTRACE(("WAL%p: acquire EXCLUSIVE-%s cnt=%d %s\n", pWal,
@@ -1076,7 +1077,7 @@ static int walIndexRecover(Wal *pWal){
assert( pWal->writeLock );
iLock = WAL_ALL_BUT_WRITE + pWal->ckptLock;
nLock = SQLITE_SHM_NLOCK - iLock;
rc = walLockExclusive(pWal, iLock, nLock);
rc = walLockExclusive(pWal, iLock, nLock, 0);
if( rc ){
return rc;
}
@@ -1610,7 +1611,7 @@ static int walBusyLock(
){
int rc;
do {
rc = walLockExclusive(pWal, lockIdx, n);
rc = walLockExclusive(pWal, lockIdx, n, 0);
}while( xBusy && rc==SQLITE_BUSY && xBusy(pBusyArg) );
return rc;
}
@@ -2043,7 +2044,7 @@ static int walIndexReadHdr(Wal *pWal, int *pChanged){
walUnlockShared(pWal, WAL_WRITE_LOCK);
rc = SQLITE_READONLY_RECOVERY;
}
}else if( SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1)) ){
}else if( SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1, 1)) ){
pWal->writeLock = 1;
if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){
badHdr = walIndexTryHdr(pWal, pChanged);
@@ -2249,7 +2250,7 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
&& (mxReadMark<pWal->hdr.mxFrame || mxI==0)
){
for(i=1; i<WAL_NREADER; i++){
rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1, 0);
if( rc==SQLITE_OK ){
mxReadMark = pInfo->aReadMark[i] = pWal->hdr.mxFrame;
mxI = i;
@@ -2505,7 +2506,7 @@ int sqlite3WalBeginWriteTransaction(Wal *pWal){
/* Only one writer allowed at a time. Get the write lock. Return
** SQLITE_BUSY if unable.
*/
rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1);
rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1, 0);
if( rc ){
return rc;
}
@@ -2650,7 +2651,7 @@ static int walRestartLog(Wal *pWal){
if( pInfo->nBackfill>0 ){
u32 salt1;
sqlite3_randomness(4, &salt1);
rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1, 0);
if( rc==SQLITE_OK ){
/* If all readers are using WAL_READ_LOCK(0) (in other words if no
** readers are currently using the WAL), then the transactions
@@ -2975,7 +2976,7 @@ int sqlite3WalCheckpoint(
/* IMPLEMENTATION-OF: R-62028-47212 All calls obtain an exclusive
** "checkpoint" lock on the database file. */
rc = walLockExclusive(pWal, WAL_CKPT_LOCK, 1);
rc = walLockExclusive(pWal, WAL_CKPT_LOCK, 1, 0);
if( rc ){
/* EVIDENCE-OF: R-10421-19736 If any other process is running a
** checkpoint operation at the same time, the lock cannot be obtained and