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Avoid locking shm-lock WAL_READ_LOCK(0) during recovery. Doing this allows

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recovery to proceed while a readonly_shm connection in unlocked mode has an
ongoing read transaction.

FossilOrigin-Name: 5190d84a296b7cf716ef43bf7b6d4d351ef1a4d650de37dc01a5ab333da7c05d
This commit is contained in:
dan
2017-11-02 11:12:03 +00:00
parent 92c02da33e
commit dea5ce36f5
4 changed files with 49 additions and 12 deletions
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14
src/wal.c
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@@ -1101,7 +1101,6 @@ static int walIndexRecover(Wal *pWal){
i64 nSize; /* Size of log file */
u32 aFrameCksum[2] = {0, 0};
int iLock; /* Lock offset to lock for checkpoint */
int nLock; /* Number of locks to hold */
/* Obtain an exclusive lock on all byte in the locking range not already
** locked by the caller. The caller is guaranteed to have locked the
@@ -1114,11 +1113,17 @@ static int walIndexRecover(Wal *pWal){
assert( WAL_CKPT_LOCK==WAL_ALL_BUT_WRITE );
assert( pWal->writeLock );
iLock = WAL_ALL_BUT_WRITE + pWal->ckptLock;
nLock = SQLITE_SHM_NLOCK - iLock;
rc = walLockExclusive(pWal, iLock, nLock);
rc = walLockExclusive(pWal, iLock, WAL_READ_LOCK(0)-iLock);
if( rc==SQLITE_OK ){
rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
if( rc!=SQLITE_OK ){
walUnlockExclusive(pWal, iLock, WAL_READ_LOCK(0)-iLock);
}
}
if( rc ){
return rc;
}
WALTRACE(("WAL%p: recovery begin...\n", pWal));
memset(&pWal->hdr, 0, sizeof(WalIndexHdr));
@@ -1256,7 +1261,8 @@ finished:
recovery_error:
WALTRACE(("WAL%p: recovery %s\n", pWal, rc ? "failed" : "ok"));
walUnlockExclusive(pWal, iLock, nLock);
walUnlockExclusive(pWal, iLock, WAL_READ_LOCK(0)-iLock);
walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
return rc;
}