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Overview
Comment:When walTryBeginRead() encounters an I/O error trying to set a lock (as opposed to SQLITE_BUSY) be sure to propagate that error back up the call stack.
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SHA1: aa2c2b67a7f50c97a44cca1af5c437bf5410869c
User & Date: drh 2010-06-02 15:43:19
Context
2010-06-02
15:59
Make sure the directory used by os_unix.c for shared-memory files is always the same, regardless of individual client permissions and environment variable settings. check-in: f97bd520 user: drh tags: trunk
15:43
When walTryBeginRead() encounters an I/O error trying to set a lock (as opposed to SQLITE_BUSY) be sure to propagate that error back up the call stack. check-in: aa2c2b67 user: drh tags: trunk
14:45
Changes to make WAL more robust against SHM locking failures and OOM errors. check-in: ebf40413 user: drh tags: trunk
Changes
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Changes to src/wal.c.

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    ** 1 and WAL_NREADER-1 are zero.  Try to initialize aReadMark[1] to
    ** be mxFrame, then retry.
    */
    rc = walLockExclusive(pWal, WAL_READ_LOCK(1), 1);
    if( rc==SQLITE_OK ){
      pInfo->aReadMark[1] = pWal->hdr.mxFrame+1;
      walUnlockExclusive(pWal, WAL_READ_LOCK(1), 1);



    }
    return WAL_RETRY;
  }else{
    if( mxReadMark < pWal->hdr.mxFrame ){
      for(i=1; i<WAL_NREADER; i++){
        rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
        if( rc==SQLITE_OK ){
          mxReadMark = pInfo->aReadMark[i] = pWal->hdr.mxFrame+1;
          mxI = i;
          walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
          break;


        }
      }
    }

    rc = walLockShared(pWal, WAL_READ_LOCK(mxI));
    if( rc ){
      return rc==SQLITE_BUSY ? WAL_RETRY : rc;







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    ** 1 and WAL_NREADER-1 are zero.  Try to initialize aReadMark[1] to
    ** be mxFrame, then retry.
    */
    rc = walLockExclusive(pWal, WAL_READ_LOCK(1), 1);
    if( rc==SQLITE_OK ){
      pInfo->aReadMark[1] = pWal->hdr.mxFrame+1;
      walUnlockExclusive(pWal, WAL_READ_LOCK(1), 1);
      rc = WAL_RETRY;
    }else if( rc==SQLITE_BUSY ){
      rc = WAL_RETRY;
    }
    return rc;
  }else{
    if( mxReadMark < pWal->hdr.mxFrame ){
      for(i=1; i<WAL_NREADER; i++){
        rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
        if( rc==SQLITE_OK ){
          mxReadMark = pInfo->aReadMark[i] = pWal->hdr.mxFrame+1;
          mxI = i;
          walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
          break;
        }else if( rc!=SQLITE_BUSY ){
          return rc;
        }
      }
    }

    rc = walLockShared(pWal, WAL_READ_LOCK(mxI));
    if( rc ){
      return rc==SQLITE_BUSY ? WAL_RETRY : rc;