diff options
Diffstat (limited to 'src/os_unix.c')
| -rw-r--r-- | src/os_unix.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/src/os_unix.c b/src/os_unix.c index 659e91f3b..91f641e05 100644 --- a/src/os_unix.c +++ b/src/os_unix.c @@ -3569,6 +3569,11 @@ static int unixShmRelease(sqlite3_file *fd){ /* ** Change the lock state for a shared-memory segment. +** +** Note that the relationship between SHAREd and EXCLUSIVE locks is a little +** different here than in posix. In xShmLock(), one can go from unlocked +** to shared and back or from unlocked to exclusive and back. But one may +** not go from shared to exclusive or from exclusive to shared. */ static int unixShmLock( sqlite3_file *fd, /* Database file holding the shared memory */ @@ -3626,7 +3631,6 @@ static int unixShmLock( ** SQLITE_BUSY. */ for(pX=pShmNode->pFirst; pX; pX=pX->pNext){ - if( pX==p ) continue; if( (pX->exclMask & mask)!=0 ){ rc = SQLITE_BUSY; break; @@ -3652,7 +3656,6 @@ static int unixShmLock( ** lock. If any do, return SQLITE_BUSY right away. */ for(pX=pShmNode->pFirst; pX; pX=pX->pNext){ - if( pX==p ) continue; if( (pX->exclMask & mask)!=0 || (pX->sharedMask & mask)!=0 ){ rc = SQLITE_BUSY; break; @@ -3665,7 +3668,7 @@ static int unixShmLock( if( rc==SQLITE_OK ){ rc = unixShmSystemLock(pShmNode, F_WRLCK, ofst+UNIX_SHM_BASE, n); if( rc==SQLITE_OK ){ - p->sharedMask &= ~mask; + assert( (p->sharedMask & mask)==0 ); p->exclMask |= mask; } } |