The wait task does not return the result

I am trying to write a function which uses Task and TaskCompletion. My problem is that after login, the result is not returned. I used similar code before and it was working. I do not know what causes for this situation. public async Task<byte[]> Si

Security thread, but does not stop the impasse?

I came across this line which states that "However, even though all operations are thread-safe, retrieval operations do not entail locking, and there is not any support for locking the entire table in a way that prevents all access"in the overal

Please help me understand this example of deadlock

For my programming languages class we have been given a simple Java deadlock example and are asked to solve it. I don't directly want the answer to this problem, I mainly want to know where my understanding is lacking. Here's the code: import java.ap

How to solve this impasse?

I have added comments in code to explain from where deadlock is occurring. Basically, There are two threads. Each thread acquires lock on an Manager object and then go for acquiring lock on static resource, which is a map of all the Manager objects i

use of spin variants in network processing

I have written a Kernel module that is interacting with net-filter hooks. The net-filter hooks operate in Softirq context. I am accessing a global data structure "Hash Table" from the softirq context as well as from Process context. The process

How to unlock tables using mysqli

How do I use the mysql statement "UNLOCK TABLES" using mysqli in php? I can't put it at the end the existing statement just by using a semi-colon, I get an error doing it that way. Here's what I tried to do "UPDATE blah blah; UNLOCK TABLES;

Stalemate when accessing StackExchange.Redis

I'm running into a deadlock situation when calling StackExchange.Redis. I don't know exactly what is going on, which is very frustrating, and I would appreciate any input that could help resolve or workaround this problem. In case you have this probl

Is it possible to replicate a transaction lock in Clojure?

In SQL it is relatively easy to replicate a transaction deadlock. ==SESSION1== begin tran update table1 set ... where ... [hold off further action - begin on next session] ==SESSION2== begin update table1 set ... where ... [hold off further action -

why does the thread continue to work after locking?

This is the example in java tutorial of Oracle about Lock object. Someone please confirms whether I interpreted the code correctly. I will consider only the first thread, because the other works the same way. First, it acquires the lock of alphonse,

JDBC PSD Transactions Cause Blocking

Question: Updated: Why does inserting a row into table A with a foreign key constraint to table B and then updating the row in table B that the inserted row in table A references in a transaction cause a deadlock? Scenario: reservation.time_slot_id h

Platform Condition Variable Issues

In our project, we need to implement os dependent abstractions (like file, socket, thread...) for each os (linux, android, osx and win). The general iter for implementing os abstraction is: Write an os independent class header which defines methods t

Deadlock in the function channel go

Why is there a deadlock even tho I just pass one and get one output from the channel? package main import "fmt" import "math/cmplx" func max(a []complex128, base int, ans chan float64, index chan int) { fmt.Printf("called for %d,%

Deadlock of database, but why?

I can't figure this one out, think i have stared my self blind on the problem. I have the following scenario on MsSql server 2012. In 10 threads (C# + NHibernate) i do this: Begin transaction (ReadCommitted) Select count(*) from MyTable1 where ... (c

How can System.out.format prevent blocking?

I've found that including a call to System.out.format in the classic Java Deadlock Tutorial will prevent deadlock from occurring, and I can't figure out why. The code below is the same as that of the tutorial, with the addition to main of System.out.

SQL Server Insert in Multiple Deadlock Threads

I insert in one table with many concurrent threads, in this Table is a AFTER INSERT Trigger which updates one field on the inserted Row. When this is executed in one thread everything is fine, but with many ones I got a Deadlock. Is there something I

MySQL Amazon RDS: Lock Timeout Exceeded

On Mysql (Amazon RDS), when I try to run the following SQL query UPDATE table1 INNER JOIN table2 USING (CommonColumn) SET table1.col1 = table2.x, table1.col2 = table2.y I get this error after around 52 seconds consistently: Error Code: 1205. Lock wai

Multithreaded lock, fun time (mid-course practice)

Here is a question my study group is arguing about: (g) Consider the following C# code: public class Demo { private static readonly object a = new object(); private static readonly object b = new object(); public static void Main (string[] args) { De

Simulate a deadlock using the stored procedure

Does anyone know how to simulate a deadlock using a stored procedure inserting or updating values? I could only do so in sybase using individual commands. Thanks, VerCreate two stored procedures. The first should start a transaction, modify table 1 (

Can not understand: using lock () but never execute code

I'm learning about threads in C#, and i get this behavior that i cant understand. The code simulates I/O operations, like files or serial port, where only one thread can access it at time, and it blocks until finishes. Four threads are started. Each

Postgres ShareRowExclusiveLock lock

I have a loading posgres server with a large amount of update operations. In postgres.conf I set the deadlock_timeout= 8s. In the log I see the following: process 3588 acquired ShareRowExclusiveLock on relation 17360 of database 16392 after 8000.000

SQL Server blocking between INSERT and SELECT

I've got a problem with multiple deadlocks on SQL server 2005. This one is between an INSERT and a SELECT statement. There are two tables. Table 1 and Table2. Table2 has Table1's PK (table1_id) as foreign key. Index on table1_id is clustered. The INS

SQL 2008 SP - cause blocking or red herring?

One of my co-workers has a stored procedure that does the following Begin tran 1) Dynamically generate a select statement. 2) Insert into table x 3) Execute the select statement End tran If this stored procedure is ran by two septate threads simultan

Tools to implement a python monitoring timer

I'm writing some code for testing multithreaded programs (student homework--likely buggy), and want to be able to detect when they deadlock. When running properly, the programs regularly produce output to stdout, so that makes it fairly straightforwa