diff options
Diffstat (limited to 'src/os_unix.c')
| -rw-r--r-- | src/os_unix.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/src/os_unix.c b/src/os_unix.c index caf22effe..e15d9d416 100644 --- a/src/os_unix.c +++ b/src/os_unix.c @@ -4589,6 +4589,12 @@ typedef struct unixShmFile unixShmFile; ** Either unixShmFile.mutex must be held or unixShmFile.nRef==0 and ** unixMutexHeld() is true when reading or writing any other field ** in this structure. +** +** To avoid deadlocks, mutex and mutexBuf are always released in the +** reverse order that they are acquired. mutexBuf is always acquired +** first and released last. This invariant is check by asserting +** sqlite3_mutex_notheld() on mutex whenever mutexBuf is acquired or +** released. */ struct unixShmFile { struct unixFileId fid; /* Unique file identifier */ @@ -5146,6 +5152,7 @@ static int unixShmGet( int rc = SQLITE_OK; if( p->lockState!=SQLITE_SHM_CHECKPOINT && p->hasMutexBuf==0 ){ + assert( sqlite3_mutex_notheld(pFile->mutex) ); sqlite3_mutex_enter(pFile->mutexBuf); p->hasMutexBuf = 1; } @@ -5184,6 +5191,7 @@ static int unixShmRelease(sqlite3_shm *pSharedMem){ unixShm *p = (unixShm*)pSharedMem; if( p->hasMutexBuf && p->lockState!=SQLITE_SHM_RECOVER ){ unixShmFile *pFile = p->pFile; + assert( sqlite3_mutex_notheld(pFile->mutex) ); sqlite3_mutex_leave(pFile->mutexBuf); p->hasMutexBuf = 0; } @@ -5246,6 +5254,7 @@ static int unixShmLock( p->id, getpid(), azLkName[p->lockState], azLkName[desiredLock])); if( desiredLock==SQLITE_SHM_RECOVER && !p->hasMutexBuf ){ + assert( sqlite3_mutex_notheld(pFile->mutex) ); sqlite3_mutex_enter(pFile->mutexBuf); p->hasMutexBuf = 1; } |