/ Check-in [3117c1b5]
Login

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Add compiler hints to disable TSAN for the routines that access the -shm file header in WAL mode using a double-read with memory barrier.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA3-256: 3117c1b5a9e348fd8d16ba9d03fdafaad8514567fb3403f72b86d6162ad40bde
User & Date: drh 2020-05-19 15:51:10
Context
2020-05-20
15:02
Back out the change from [7fab1393c2b22b1f] that tries to convert invalid surrogate characters in UTF16 into the replacement character 0xfffd, as we find that this breaks some software. (check-in: 4218c7b7 user: drh tags: trunk)
2020-05-19
15:51
Add compiler hints to disable TSAN for the routines that access the -shm file header in WAL mode using a double-read with memory barrier. (check-in: 3117c1b5 user: drh tags: trunk)
15:40
In os_win.c, avoid calling sqlite3_uri_boolean() on anything other than a main-db filename. (check-in: cb0a18e6 user: dan tags: trunk)
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/wal.c.

695
696
697
698
699
700
701













702
703
704
705
706
707
708
709
710
711
712
713
714
....
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
*/
static void walShmBarrier(Wal *pWal){
  if( pWal->exclusiveMode!=WAL_HEAPMEMORY_MODE ){
    sqlite3OsShmBarrier(pWal->pDbFd);
  }
}














/*
** Write the header information in pWal->hdr into the wal-index.
**
** The checksum on pWal->hdr is updated before it is written.
*/
static void walIndexWriteHdr(Wal *pWal){
  volatile WalIndexHdr *aHdr = walIndexHdr(pWal);
  const int nCksum = offsetof(WalIndexHdr, aCksum);

  assert( pWal->writeLock );
  pWal->hdr.isInit = 1;
  pWal->hdr.iVersion = WALINDEX_MAX_VERSION;
  walChecksumBytes(1, (u8*)&pWal->hdr, nCksum, 0, pWal->hdr.aCksum);
................................................................................
** If and only if the read is consistent and the header is different from
** pWal->hdr, then pWal->hdr is updated to the content of the new header
** and *pChanged is set to 1.
**
** If the checksum cannot be verified return non-zero. If the header
** is read successfully and the checksum verified, return zero.
*/
static int walIndexTryHdr(Wal *pWal, int *pChanged){
  u32 aCksum[2];                  /* Checksum on the header content */
  WalIndexHdr h1, h2;             /* Two copies of the header content */
  WalIndexHdr volatile *aHdr;     /* Header in shared memory */

  /* The first page of the wal-index must be mapped at this point. */
  assert( pWal->nWiData>0 && pWal->apWiData[0] );








>
>
>
>
>
>
>
>
>
>
>
>
>





|







 







|







695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
....
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
*/
static void walShmBarrier(Wal *pWal){
  if( pWal->exclusiveMode!=WAL_HEAPMEMORY_MODE ){
    sqlite3OsShmBarrier(pWal->pDbFd);
  }
}

/*
** Add the SQLITE_NO_TSAN as part of the return-type of a function
** definition as a hint that the function contains constructs that
** might give false-positive TSAN warnings.
**
** See tag-20200519-1.
*/
#if defined(__clang__) && !defined(SQLITE_NO_TSAN)
# define SQLITE_NO_TSAN __attribute__((no_sanitize_thread))
#else
# define SQLITE_NO_TSAN
#endif

/*
** Write the header information in pWal->hdr into the wal-index.
**
** The checksum on pWal->hdr is updated before it is written.
*/
static SQLITE_NO_TSAN void walIndexWriteHdr(Wal *pWal){
  volatile WalIndexHdr *aHdr = walIndexHdr(pWal);
  const int nCksum = offsetof(WalIndexHdr, aCksum);

  assert( pWal->writeLock );
  pWal->hdr.isInit = 1;
  pWal->hdr.iVersion = WALINDEX_MAX_VERSION;
  walChecksumBytes(1, (u8*)&pWal->hdr, nCksum, 0, pWal->hdr.aCksum);
................................................................................
** If and only if the read is consistent and the header is different from
** pWal->hdr, then pWal->hdr is updated to the content of the new header
** and *pChanged is set to 1.
**
** If the checksum cannot be verified return non-zero. If the header
** is read successfully and the checksum verified, return zero.
*/
static SQLITE_NO_TSAN int walIndexTryHdr(Wal *pWal, int *pChanged){
  u32 aCksum[2];                  /* Checksum on the header content */
  WalIndexHdr h1, h2;             /* Two copies of the header content */
  WalIndexHdr volatile *aHdr;     /* Header in shared memory */

  /* The first page of the wal-index must be mapped at this point. */
  assert( pWal->nWiData>0 && pWal->apWiData[0] );