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Bug fix in the unix locking code. (CVS 1574)

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FossilOrigin-Name: dcad244f58453d23f2bcb749dcea077434bbd08c
This commit is contained in:
drh
2004-06-12 02:17:14 +00:00
parent 2a764eb0cd
commit 3cde3bb0da
5 changed files with 40 additions and 29 deletions
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37
src/os_unix.c
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@@ -733,7 +733,6 @@ int sqlite3OsLock(OsFile *id, int locktype){
*/
if( (id->locktype!=pLock->locktype &&
(pLock->locktype>=PENDING_LOCK || locktype>SHARED_LOCK))
|| (locktype==EXCLUSIVE_LOCK && pLock->cnt>1)
){
rc = SQLITE_BUSY;
goto end_lock;
@@ -757,16 +756,13 @@ int sqlite3OsLock(OsFile *id, int locktype){
lock.l_len = 1L;
lock.l_whence = SEEK_SET;
/* If control gets to this point, then actually go ahead and make
** operating system calls for the specified lock.
/* A PENDING lock is needed before acquiring a SHARED lock and before
** acquiring an EXCLUSIVE lock. For the SHARED lock, the PENDING will
** be released.
*/
if( locktype==SHARED_LOCK ){
assert( pLock->cnt==0 );
assert( pLock->locktype==0 );
/* Temporarily grab a PENDING lock. This prevents new SHARED locks from
** being formed if a PENDING lock is already held.
*/
if( locktype==SHARED_LOCK
|| (locktype==EXCLUSIVE_LOCK && id->locktype<PENDING_LOCK)
){
lock.l_type = F_RDLCK;
lock.l_start = PENDING_BYTE;
s = fcntl(id->h, F_SETLK, &lock);
@@ -774,6 +770,15 @@ int sqlite3OsLock(OsFile *id, int locktype){
rc = (errno==EINVAL) ? SQLITE_NOLFS : SQLITE_BUSY;
goto end_lock;
}
}
/* If control gets to this point, then actually go ahead and make
** operating system calls for the specified lock.
*/
if( locktype==SHARED_LOCK ){
assert( pLock->cnt==0 );
assert( pLock->locktype==0 );
/* Now get the read-lock */
lock.l_start = SHARED_FIRST;
@@ -792,8 +797,12 @@ int sqlite3OsLock(OsFile *id, int locktype){
id->pOpen->nLock++;
pLock->cnt = 1;
}
}else if( locktype==EXCLUSIVE_LOCK && pLock->cnt>1 ){
/* We are trying for an exclusive lock but another thread in this
** same process is still holding a shared lock. */
rc = SQLITE_BUSY;
}else{
/* The request was for a RESERVED, PENDING or EXCLUSIVE lock. It is
/* The request was for a RESERVED or EXCLUSIVE lock. It is
** assumed that there is a SHARED or greater lock on the file
** already.
*/
@@ -803,9 +812,6 @@ int sqlite3OsLock(OsFile *id, int locktype){
case RESERVED_LOCK:
lock.l_start = RESERVED_BYTE;
break;
case PENDING_LOCK:
lock.l_start = PENDING_BYTE;
break;
case EXCLUSIVE_LOCK:
lock.l_start = SHARED_FIRST;
lock.l_len = SHARED_SIZE;
@@ -822,6 +828,9 @@ int sqlite3OsLock(OsFile *id, int locktype){
if( rc==SQLITE_OK ){
id->locktype = locktype;
pLock->locktype = locktype;
}else if( locktype==EXCLUSIVE_LOCK ){
id->locktype = PENDING_LOCK;
pLock->locktype = PENDING_LOCK;
}
end_lock: