If you are using InnoDB or any row-level transactional RDBMS, then it is possible that any write transaction can cause a deadlock, even in perfectly normal situations. Larger tables, larger writes, and long transaction blocks will often increase the likelihood of deadlocks occurring. In your situation, it’s probably a combination of these. The only way … Read more
I would interpret the message as a deadlock on some combination of Lock resources or Communication Buffer resources. “Lock resources” are ordinary object locks, and “Communication Buffer resources” are exchangeEvents used for combining results of parallel queries. These are described further in https://blogs.msdn.microsoft.com/bartd/2008/09/24/todays-annoyingly-unwieldy-term-intra-query-parallel-thread-deadlocks/ where the relevant paragraph is: An “exchangeEvent” resource indicates the presence of … Read more
My init understanding is that a Select query won’t lock a table, or won’t cause a deadlock This understanding is wrong. SELECT queries take shared locks on the rows they analyze. Shared locks may conflict exclusive locks from update/delete/insert statements. Two SELECT statements are not going to deadlock, but a SELECT can deadlock with an … Read more
You can set up a worker thread to process all requests in a deterministic way, so nobody gets starved. This strategy would be reasonably efficient and immune to livelock. — yes, this is a horrible name createManagerFactory :: a -> IO ((IO a), IO (((a -> a) -> IO a))) IO a is an action … Read more
The problem you describe is not handled by the database, and from my experience is not entirely handled by Hibernate either. You have to take explicit steps to avoid it being a problem. Hibernate does some of the work for you. As per the previous answer, Hibernate ensures that within an isolated flush the inserts, … Read more
In the simple case given, unlocking in the reverse order is not necessary to avoid a deadlock. However, as the code gets more complicated, unlocking in the reverse order helps you maintain proper lock ordering. Consider: A.lock(); B.lock(); Foo(); A.unlock(); Bar(); B.unlock(); If Bar() attempts to reacquire A, you’ve effectively broken your lock ordering. You’re … Read more
Update: This recent MSDN article, Tools And Techniques to Identify Concurrency Issues, might also be of interest Stephen Toub in the MSDN article Deadlock monitor states the following four conditions necessary for deadlocks to occur: A limited number of a particular resource. In the case of a monitor in C# (what you use when you … Read more
This can happen because a select takes a lock out on two different indexes, meanwhile an update takes a lock out on the same indexes in the opposite order. The select needs two indexes because the first index doesn’t cover all of the columns it needs to access; the update needs two indexes because if … Read more
When a thread object goes out of scope and it is in joinable state, the program is terminated. The Standard Committee had two other options for the destructor of a joinable thread. It could quietly join — but join might never return if the thread is stuck. Or it could detach the thread (a detached … Read more
Your problem is because you are blocking the UI thread when you call .Result and you told the continuation after Task.Delay to run on the UI thread. So you are blocking the UI waiting for a task that is blocked on waiting for the UI to become free, a classic deadlock. Two solutions. First make … Read more