On Mon, Mar 12, 2012 at 1:23 AM, James Russell Moore <
[email protected]> wrote:
> Hello, I just saw what could be a possible typo when acquiring a pending
> lock.
>
> In the current version of the amalgamation (3.7.10) line 23200 there is the
> following code:
>
The code in question is part of the OS/2 driver, which is contributed
code. Nobody on the core SQLite team has the capability of compiling or
testing SQLite on OS/2.
If any OS/2 users see this, can you please look into the matter for us?
>
> /* Acquire a PENDING lock
> */
> if( locktype==EXCLUSIVE_LOCK && res == NO_ERROR ){
> newLocktype = PENDING_LOCK;
> gotPendingLock = 0;
> OSTRACE(( "LOCK %d acquire pending lock. pending lock boolean unset.\n",
> pFile->h ));
> }
>
> In the surroundings of that snippet there are checks to acquire the
> different kinds of locks but in all of them the lock type is tested against
> what's is being acquired. Furthermore, the next test following this one to
> acquire an exclusive lock has the same condition, which wouldn't
> be necessary if the current code for the pending lock is correct:
>
> /* Acquire an EXCLUSIVE lock
> */
> if( locktype==EXCLUSIVE_LOCK && res == NO_ERROR ){
> assert( pFile->locktype>=SHARED_LOCK );
> res = unlockReadLock(pFile);
> ...
>
> In line 33996 the same situation happens:
>
> /* Acquire a PENDING lock
> */
> if( locktype==EXCLUSIVE_LOCK && res ){
> newLocktype = PENDING_LOCK;
> gotPendingLock = 0;
> }
>
> It could be nothing, since I don't have a deep knowledge on how SQLite is
> implemented, but in the documentation in
> SQLite.org<http://sqlite.org/lockingv3.html>the following text
> appears:
>
> "A PENDING lock means that the process holding the lock wants to write to
> the database as soon as possible and is just waiting on all current SHARED
> locks to clear so that it can get an EXCLUSIVE lock."
>
> Given the name of the variables involved in those pieces of code going from
> an EXCLUSIVE lock to a PENDING lock doesn't seem logical. I've attached a
> patch on how I think is correct in case it is preferable (available
> here<http://pastebin.com/phEUEAiY>
> too).
>
> Sorry for the trouble caused if the current state is correct.
>
> Kind regards,
> James Russell.
>
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>
>
--
D. Richard Hipp
[email protected]
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