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Overview
| Comment: | In lsm (not SQLite), avoid opening the *-shm file before the database file is locked. Otherwise, there is a race condition whereby a connection in another process process may unlink() it while it is still in use. |
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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA3-256: |
c8b8b9b573665c2b4d278bb679a48ac4 |
| User & Date: | dan 2017-10-23 11:48:00 |
Context
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2017-10-23
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| 17:36 | Cleanup a test database file prior to using it. check-in: e1bf5e1d user: mistachkin tags: trunk | |
| 11:48 | In lsm (not SQLite), avoid opening the *-shm file before the database file is locked. Otherwise, there is a race condition whereby a connection in another process process may unlink() it while it is still in use. check-in: c8b8b9b5 user: dan tags: trunk | |
| 07:52 | Fix minor test script problems revealed by releasetest.tcl. check-in: 15e87d9b user: dan tags: trunk | |
Changes
Changes to ext/lsm1/lsm_shared.c.
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const int nUsMax = 100000; /* Max value for nUs */ int nUs = 1000; /* us to wait between DMS1 attempts */ int rc; /* Obtain a pointer to the shared-memory header */ assert( pDb->pShmhdr==0 ); assert( pDb->bReadonly==0 ); rc = lsmShmCacheChunks(pDb, 1); if( rc!=LSM_OK ) return rc; pDb->pShmhdr = (ShmHeader *)pDb->apShm[0]; /* Block for an exclusive lock on DMS1. This lock serializes all calls ** to doDbConnect() and doDbDisconnect() across all processes. */ while( 1 ){ rc = lsmShmLock(pDb, LSM_LOCK_DMS1, LSM_LOCK_EXCL, 1); if( rc!=LSM_BUSY ) break; lsmEnvSleep(pDb->pEnv, nUs); nUs = nUs * 2; if( nUs>nUsMax ) nUs = nUsMax; } if( rc!=LSM_OK ){ pDb->pShmhdr = 0; return rc; } /* Try an exclusive lock on DMS2/DMS3. If successful, this is the first ** and only connection to the database. In this case initialize the ** shared-memory and run log file recovery. */ assert( LSM_LOCK_DMS3==1+LSM_LOCK_DMS2 ); rc = lsmShmTestLock(pDb, LSM_LOCK_DMS2, 2, LSM_LOCK_EXCL); if( rc==LSM_OK ){ |
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const int nUsMax = 100000; /* Max value for nUs */
int nUs = 1000; /* us to wait between DMS1 attempts */
int rc;
/* Obtain a pointer to the shared-memory header */
assert( pDb->pShmhdr==0 );
assert( pDb->bReadonly==0 );
/* Block for an exclusive lock on DMS1. This lock serializes all calls
** to doDbConnect() and doDbDisconnect() across all processes. */
while( 1 ){
rc = lsmShmLock(pDb, LSM_LOCK_DMS1, LSM_LOCK_EXCL, 1);
if( rc!=LSM_BUSY ) break;
lsmEnvSleep(pDb->pEnv, nUs);
nUs = nUs * 2;
if( nUs>nUsMax ) nUs = nUsMax;
}
if( rc==LSM_OK ){
rc = lsmShmCacheChunks(pDb, 1);
}
if( rc!=LSM_OK ) return rc;
pDb->pShmhdr = (ShmHeader *)pDb->apShm[0];
/* Try an exclusive lock on DMS2/DMS3. If successful, this is the first
** and only connection to the database. In this case initialize the
** shared-memory and run log file recovery. */
assert( LSM_LOCK_DMS3==1+LSM_LOCK_DMS2 );
rc = lsmShmTestLock(pDb, LSM_LOCK_DMS2, 2, LSM_LOCK_EXCL);
if( rc==LSM_OK ){
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