Code looks good. 'syncActive.unlock()' must occur after 'state =
Committed'. It seems to me that marking a transaction as committed sand
telling other about it should naturally be done at the end of
Transaction::commit as it is now. I have asked Jim to comment, but no
response yet.
>-----Original Message-----
>From: Vladislav Vaintroub [mailto:vvaintroub@stripped]
>Sent: Tuesday, August 26, 2008 10:37 AM
>To: commits@stripped
>Subject: bzr commit into mysql-6.0-falcon branch (vvaintroub:2799)
Bug#38947
>
>#At file:///C:/bzr/mysql-6.0-falcon-team/
>
> 2799 Vladislav Vaintroub 2008-08-26
> Bug #38947 UPDATE threads in endless Table::fetchForUpdate loop =
>livelock
>
> Problem: in Table::fetchForUpdate() there is a small possibility for
a
> race condition - if record belongs to transaction that is being
>committed
> currently and the state of this transaction is still Active, but
>syncActive
> is already unlocked. This causes re-fetch() in the fetch thread
>without
> any wait, instead of waiting for falcon_lock_wait_timeout seconds.
>
> This is fixed by moving signaling waiters via syncActive.unlock(),
> after transaction state has changed from active to committed.
>modified:
> storage/falcon/Transaction.cpp
>
>=== modified file 'storage/falcon/Transaction.cpp'
>--- a/storage/falcon/Transaction.cpp 2008-08-25 18:24:59 +0000
>+++ b/storage/falcon/Transaction.cpp 2008-08-26 15:36:02 +0000
>@@ -275,7 +275,6 @@ void Transaction::commit()
> releaseRecordLocks();
>
> database->serialLog->preCommit(this);
>- syncActive.unlock();
>
>
>
>@@ -303,10 +302,9 @@ void Transaction::commit()
> database->flushInversion(this);
>
> // Transfer transaction from active list to committed list, set
>committed state
>-
>- Sync syncCommitted(&transactionManager-
>>committedTransactions.syncObject, "Transaction::commit(2)");
> Sync syncActiveTransactions(&transactionManager-
>>activeTransactions.syncObject, "Transaction::commit(3)");
>-
>+ Sync syncCommitted(&transactionManager-
>>committedTransactions.syncObject, "Transaction::commit(2)");
>+
> syncActiveTransactions.lock(Exclusive);
> syncCommitted.lock(Exclusive);
>
>@@ -316,6 +314,8 @@ void Transaction::commit()
>
> syncCommitted.unlock();
> syncActiveTransactions.unlock();
>+
>+ syncActive.unlock(); // signal waiting transactions
>
> database->commit(this);
>
>
>
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