Hi Ken,
thanks for the code, but I guess it will still crash:
Ken wrote:
> Marcus try something like this pseudo code:
>
> local_Exec( exec_Str) {
> *pStmt = NULL;
>
> rc = prepare_v2 (exec_Str)
> if (rc != SQLITE_OK) goto exec_err
ok, but this usually works without a BUSY state. so no problem here.
>
> rc = step ( );
This may now generate a BUSY or LOCKED state and fails.
Same as in my code except that the loop is outside.
> if (rc != SQLITE_OK or SQLITE_DONE ) goto exec_err
>
> rc = finalize( )
> if rc != SQLITE_OK ) goto exec_err
>
> return SQLITE_OK;
> :exec_err
if I come here from the step() error, I still have the same problem,
and I'm sure it will still crash in sqlite_finalize. Or do you think
it is a problem that I call Step multible times in case it returns a
busy state ?
Maybe the Step() call allready frees the pStmt because it was
trying to do an exclusive transaction, maybe a special handling for this
SQL statement ?
If nobody else has an explanation it seems that I'll have to run it in
a debugger to see where it actually crashes inside finalize... ;)
Thanks for the reply
Marcus
> if (pStmt) sqlite_finalize;
> return rc ;
> }
>
> ==============================
> code to lock:
>
> do
> {
> rc = local_exec(db, "BEGIN EXCLUSIVE TRANSACTION;", -1, 0);
>
> if( (rc == SQLITE_BUSY) || (rc == SQLITE_LOCKED) )
> {
> n++;
> Sleep(SQLTM_TIME);
> }
> }while( (n < SQLTM_COUNT) && ((rc == SQLITE_BUSY)
> || (rc == SQLITE_LOCKED)));
>
> ==============================================================
>
>
>
> --- On Wed, 12/3/08, Marcus Grimm <[EMAIL PROTECTED]> wrote:
>
>> From: Marcus Grimm <[EMAIL PROTECTED]>
>> Subject: [sqlite] Transaction Timeout and crash
>> To: "General Discussion of SQLite Database" <sqlite-users@sqlite.org>
>> Date: Wednesday, December 3, 2008, 4:15 AM
>> Hi all,
>>
>> while doing a stress test on my embedded server application
>> I'm noting a crash in sqlite3_finalize that I don't
>> understand,
>> and I'm wondering if I'm doing the right error
>> handling.
>>
>> Background: In order to encapsulate writings to the tables
>> I'm using
>> BEGIN EXCLUSIVE TRANSACTION to block all other threads from
>> reading and writing. Of course this requires a timeout and
>> busy
>> handling when trying to acquire the exclusive lock.
>>
>> So the code looks like:
>>
>> ---------------------------------------
>> /** Obtain exclusive lock **/
>> n = 0;
>> do
>> {
>> rc = sqlite3_prepare_v2(db, "BEGIN EXCLUSIVE
>> TRANSACTION;", -1, &stmt, 0);
>>
>> if( (rc == SQLITE_BUSY) || (rc == SQLITE_LOCKED) )
>> {
>> n++;
>> Sleep(SQLTM_TIME);
>> }
>> }while( (n < SQLTM_COUNT) && ((rc ==
>> SQLITE_BUSY) || (rc == SQLITE_LOCKED)));
>>
>> if( n == SQLTM_COUNT )
>> return(TIMEOUT_ERROR); /** --> Timeout during
>> prepare, never happends so far **/
>>
>> n = 0;
>> do
>> {
>> rc = sqlite3_step(stmt);
>> if( (rc == SQLITE_BUSY) || (rc == SQLITE_LOCKED) )
>> {
>> Sleep(SQLTM_TIME);
>> n++;
>> }
>> }while( (n < SQLTM_COUNT) && ((rc ==
>> SQLITE_BUSY) || (rc == SQLITE_LOCKED)));
>>
>> /** we are done **/
>> sqlite3_finalize(stmt); /** <<- crash if timeout
>> occurs **/
>>
>> if( n == SQLTM_COUNT )
>> return(TIMEOUT_ERROR);
>>
>> ------------------------
>>
>> The problem is that it crashes in the sqlite3_finalize
>> function in case the
>> sqlite3_step doesn't actually did something and the
>> timeout condition
>> becames true.
>> My feeling is that it occurs only when trying to get the
>> exclusive transaction;
>> A simple "SELECT *" that runs into a timeout
>> doesn't crash when using sqlite3_finalize.
>>
>> Before starting to deeper debugging this, I would like to
>> ask if there
>> is an advice or known issue concerning the sqlite3_finalize
>> when a
>> step was not successful due to busy or locking state.
>> It is not allowed to call this function in this case ?
>> But then: How to free the statement, succesfully created by
>> sqlite3_prepare_v2 ?
>>
>> I'm using sqlite 3.6.6.2, compiled using MSVS 2008, and
>> of course threadsafe.
>> I'm not using any timeout callback or timeout value
>> settings since I'm handling
>> this by my selve like in the code above.
>>
>> Thank you in advance.
>>
>> Marcus
>>
>>
>>
>> _______________________________________________
>> sqlite-users mailing list
>> sqlite-users@sqlite.org
>> http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
> _______________________________________________
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> sqlite-users@sqlite.org
> http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
>
--
Marcus Grimm, MedCom GmbH Darmstadt, Rundeturmstr. 12, 64283 Darmstadt
Tel: +49(0)6151-95147-10
Fax: +49(0)6151-95147-20
--------------------------------------------------
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