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Overview
| Comment: | Try to identify the places in WAL code where thread-safety depends on the underlying architecture supporting atomic load and store of aligned 32-bit values. |
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| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA3-256: |
47d44be4a68d377d0049a12b2587dbbc |
| User & Date: | drh 2018-08-30 20:28:18.073 |
Context
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2018-08-31
| ||
| 19:00 | If a call to sqlite3_snapshot_open() fails because the requested snapshot no longer exists, return SQLITE_ERROR_SNAPSHOT instead of SQLITE_BUSY_SNAPSHOT. (check-in: e07923128b user: dan tags: trunk) | |
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2018-08-30
| ||
| 20:28 | Try to identify the places in WAL code where thread-safety depends on the underlying architecture supporting atomic load and store of aligned 32-bit values. (check-in: 47d44be4a6 user: drh tags: trunk) | |
| 18:53 | Give the debugging routine print_pager_stats() external linkage in order to suppress harmless compiler and TSAN warnings. (check-in: ff4dc08298 user: drh tags: trunk) | |
Changes
Changes to src/wal.c.
| ︙ | ︙ | |||
254 255 256 257 258 259 260 261 262 263 264 265 266 267 | #if defined(SQLITE_TEST) && defined(SQLITE_DEBUG) int sqlite3WalTrace = 0; # define WALTRACE(X) if(sqlite3WalTrace) sqlite3DebugPrintf X #else # define WALTRACE(X) #endif /* ** The maximum (and only) versions of the wal and wal-index formats ** that may be interpreted by this version of SQLite. ** ** If a client begins recovering a WAL file and finds that (a) the checksum ** values in the wal-header are correct and (b) the version field is not ** WAL_MAX_VERSION, recovery fails and SQLite returns SQLITE_CANTOPEN. | > > > > > > > > > > > > | 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 | #if defined(SQLITE_TEST) && defined(SQLITE_DEBUG) int sqlite3WalTrace = 0; # define WALTRACE(X) if(sqlite3WalTrace) sqlite3DebugPrintf X #else # define WALTRACE(X) #endif /* ** WAL mode depends on atomic aligned 32-bit loads and stores in a few ** places. The following macros try to make this explicit. */ #if GCC_VESRION>=5004000 # define AtomicLoad(PTR) __atomic_load_n((PTR),__ATOMIC_RELAXED) # define AtomicStore(PTR,VAL) __atomic_store_n((PTR),(VAL),__ATOMIC_RELAXED) #else # define AtomicLoad(PTR) (*(PTR)) # define AtomicStore(PTR,VAL) (*(PTR) = (VAL)) #endif /* ** The maximum (and only) versions of the wal and wal-index formats ** that may be interpreted by this version of SQLite. ** ** If a client begins recovering a WAL file and finds that (a) the checksum ** values in the wal-header are correct and (b) the version field is not ** WAL_MAX_VERSION, recovery fails and SQLite returns SQLITE_CANTOPEN. |
| ︙ | ︙ | |||
2551 2552 2553 2554 2555 2556 2557 |
mxFrame = pWal->hdr.mxFrame;
#ifdef SQLITE_ENABLE_SNAPSHOT
if( pWal->pSnapshot && pWal->pSnapshot->mxFrame<mxFrame ){
mxFrame = pWal->pSnapshot->mxFrame;
}
#endif
for(i=1; i<WAL_NREADER; i++){
| | | | 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 |
mxFrame = pWal->hdr.mxFrame;
#ifdef SQLITE_ENABLE_SNAPSHOT
if( pWal->pSnapshot && pWal->pSnapshot->mxFrame<mxFrame ){
mxFrame = pWal->pSnapshot->mxFrame;
}
#endif
for(i=1; i<WAL_NREADER; i++){
u32 thisMark = AtomicLoad(pInfo->aReadMark+i);
if( mxReadMark<=thisMark && thisMark<=mxFrame ){
assert( thisMark!=READMARK_NOT_USED );
mxReadMark = thisMark;
mxI = i;
}
}
if( (pWal->readOnly & WAL_SHM_RDONLY)==0
&& (mxReadMark<mxFrame || mxI==0)
){
for(i=1; i<WAL_NREADER; i++){
rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
if( rc==SQLITE_OK ){
mxReadMark = AtomicStore(pInfo->aReadMark+i,mxFrame);
mxI = i;
walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
break;
}else if( rc!=SQLITE_BUSY ){
return rc;
}
}
|
| ︙ | ︙ | |||
2616 2617 2618 2619 2620 2621 2622 | ** A) on the basis that there is a newer version (version B) of the same ** page later in the wal file. But if version B happens to like past ** frame pWal->hdr.mxFrame - then the client would incorrectly assume ** that it can read version A from the database file. However, since ** we can guarantee that the checkpointer that set nBackfill could not ** see any pages past pWal->hdr.mxFrame, this problem does not come up. */ | | | | 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 |
** A) on the basis that there is a newer version (version B) of the same
** page later in the wal file. But if version B happens to like past
** frame pWal->hdr.mxFrame - then the client would incorrectly assume
** that it can read version A from the database file. However, since
** we can guarantee that the checkpointer that set nBackfill could not
** see any pages past pWal->hdr.mxFrame, this problem does not come up.
*/
pWal->minFrame = AtomicLoad(&pInfo->nBackfill)+1;
walShmBarrier(pWal);
if( AtomicLoad(pInfo->aReadMark+mxI)!=mxReadMark
|| memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr))
){
walUnlockShared(pWal, WAL_READ_LOCK(mxI));
return WAL_RETRY;
}else{
assert( mxReadMark<=pWal->hdr.mxFrame );
pWal->readLock = (i16)mxI;
|
| ︙ | ︙ |