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Overview
| Comment: | Define an invariant to guarantee deadlock-free operation of SHM in os_unix.c and check that invariant with assert() statements. |
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| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | wal |
| Files: | files | file ages | folders |
| SHA1: |
6af2dca75b8139134ea394c1d71aefc6 |
| User & Date: | drh 2010-05-01 17:57:36.000 |
Context
|
2010-05-03
| ||
| 08:04 | Add the sqlite3_wal_checkpoint() and sqlite3_wal_autocheckpoint() APIs. (check-in: 9803196dec user: dan tags: wal) | |
|
2010-05-01
| ||
| 18:23 | Remove the xShmPush and xShmPull methods from the VFS. (check-in: 69e07fdbde user: drh tags: wal) | |
| 17:57 | Define an invariant to guarantee deadlock-free operation of SHM in os_unix.c and check that invariant with assert() statements. (check-in: 6af2dca75b user: drh tags: wal) | |
| 17:50 | Rework mutexes on the SHM implemention for os_unix to avoid a deadlock during WAL recovery. (check-in: 1a0f69bef2 user: drh tags: wal) | |
Changes
Changes to src/os_unix.c.
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**
** fid
** zFilename
**
** Either unixShmFile.mutex must be held or unixShmFile.nRef==0 and
** unixMutexHeld() is true when reading or writing any other field
** in this structure.
*/
struct unixShmFile {
struct unixFileId fid; /* Unique file identifier */
sqlite3_mutex *mutex; /* Mutex to access this object */
sqlite3_mutex *mutexBuf; /* Mutex to access zBuf[] */
char *zFilename; /* Name of the file */
int h; /* Open file descriptor */
| > > > > > > | 4585 4586 4587 4588 4589 4590 4591 4592 4593 4594 4595 4596 4597 4598 4599 4600 4601 4602 4603 4604 |
**
** fid
** zFilename
**
** 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 */
sqlite3_mutex *mutex; /* Mutex to access this object */
sqlite3_mutex *mutexBuf; /* Mutex to access zBuf[] */
char *zFilename; /* Name of the file */
int h; /* Open file descriptor */
|
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void **ppBuf /* Write mapping buffer origin here */
){
unixShm *p = (unixShm*)pSharedMem;
unixShmFile *pFile = p->pFile;
int rc = SQLITE_OK;
if( p->lockState!=SQLITE_SHM_CHECKPOINT && p->hasMutexBuf==0 ){
sqlite3_mutex_enter(pFile->mutexBuf);
p->hasMutexBuf = 1;
}
sqlite3_mutex_enter(pFile->mutex);
if( pFile->szMap==0 || reqMapSize>pFile->szMap ){
int actualSize;
if( unixShmSize(pSharedMem, -1, &actualSize)==SQLITE_OK
| > | 5148 5149 5150 5151 5152 5153 5154 5155 5156 5157 5158 5159 5160 5161 5162 |
void **ppBuf /* Write mapping buffer origin here */
){
unixShm *p = (unixShm*)pSharedMem;
unixShmFile *pFile = p->pFile;
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;
}
sqlite3_mutex_enter(pFile->mutex);
if( pFile->szMap==0 || reqMapSize>pFile->szMap ){
int actualSize;
if( unixShmSize(pSharedMem, -1, &actualSize)==SQLITE_OK
|
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** really want to release the lock, so in that case too, this routine
** is a no-op.
*/
static int unixShmRelease(sqlite3_shm *pSharedMem){
unixShm *p = (unixShm*)pSharedMem;
if( p->hasMutexBuf && p->lockState!=SQLITE_SHM_RECOVER ){
unixShmFile *pFile = p->pFile;
sqlite3_mutex_leave(pFile->mutexBuf);
p->hasMutexBuf = 0;
}
return SQLITE_OK;
}
/*
| > | 5187 5188 5189 5190 5191 5192 5193 5194 5195 5196 5197 5198 5199 5200 5201 |
** really want to release the lock, so in that case too, this routine
** is a no-op.
*/
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;
}
return SQLITE_OK;
}
/*
|
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return SQLITE_OK;
}
OSTRACE(("SHM-LOCK shmid-%d, pid-%d request %s->%s\n",
p->id, getpid(), azLkName[p->lockState], azLkName[desiredLock]));
if( desiredLock==SQLITE_SHM_RECOVER && !p->hasMutexBuf ){
sqlite3_mutex_enter(pFile->mutexBuf);
p->hasMutexBuf = 1;
}
sqlite3_mutex_enter(pFile->mutex);
switch( desiredLock ){
case SQLITE_SHM_UNLOCK: {
assert( p->lockState!=SQLITE_SHM_RECOVER );
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return SQLITE_OK;
}
OSTRACE(("SHM-LOCK shmid-%d, pid-%d request %s->%s\n",
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;
}
sqlite3_mutex_enter(pFile->mutex);
switch( desiredLock ){
case SQLITE_SHM_UNLOCK: {
assert( p->lockState!=SQLITE_SHM_RECOVER );
|
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