locking

问题 I am writing a script to retrieve WMI info from many computers at the same time then write this info in a text file: f = open("results.txt", 'w+') ## to clean the results file before the start def filesize(asset): f = open("results.txt", 'a+') c = wmi.WMI(asset) wql = 'SELECT FileSize,Name FROM CIM_DataFile where (Drive="D:" OR Drive="E:") and Caption like "%file%"' for item in c.query(wql): print >> f, item.Name.split("\\")[2].strip().upper(), str(item.FileSize) class myThread (threading

问题 I am confused about the subject of locking in Oracle. As far as my research has lead me, you can use the FOR UPDATE NOWAIT/WAIT to lock rows. I want to implement my locking this way. Once I issue the FOR UPDATE , the row will then be locked and I can check for mutations. I have a versionNumber column that increments by 1 everytime the table is updated. Can i use this versionNumber to verify the row has or hasn't mutated? something like if (:new.versionNum != :old.versionNum) raise_application

问题 Update : For the benefit of anyone reading this, since .NET 4, the lock is unnecessary due to changes in synchronization of auto-generated events, so I just use this now: public static void Raise<T>(this EventHandler<T> handler, object sender, T e) where T : EventArgs { if (handler != null) { handler(sender, e); } } And to raise it: SomeEvent.Raise(this, new FooEventArgs()); Having been reading one of Jon Skeet's articles on multithreading, I've tried to encapsulate the approach he advocates

问题 I'm very new to Node.js and I'm sure there's an easy answer to this, I just can't find it :( I'm using the filesystem to hold 'packages' (folders with a status extensions 'mypackage.idle') Users can perform actions on these which would cause the status to go to something like 'qa', or 'deploying' etc... If the server is accepting lots of requests and multiple requests come in for the same package how would I check the status and then perform an action, which would change the status,

问题 Update: This looks like a memory issue. A 3.8 Gb Hprof file indicated that the JVM was dumping-its-heap when this "blocking" occurred. Our operations team saw that the site wasn't responding, took a stack trace, then shut down the instance. I believe they shut down the site before the heap dump finished. The log had no errors/exceptions/evidence of problems--probably because the JVM was killed before it could generate an error message. Original Question We had a recent situation where the

问题 MSDN gives the following warning about the lock keyword in C#: In general, avoid locking on a public type, or instances beyond your code's control. The common constructs lock (this), lock (typeof (MyType)), and lock ("myLock") violate this guideline: * lock (this) is a problem if the instance can be accessed publicly. * lock (typeof (MyType)) is a problem if MyType is publicly accessible. Yet it gives no solid reasoning for it. The lock(this) is explained here on SO. I'm interested in lock

问题 I'm working on some Python code modeled on Apache's MPM prefork server. I am more an applications programmer than a network programmer and it's been 10 years since I read Stevens, so I'm trying to get up to speed in understanding the code. I found a short description of how Apache's prefork code works, by Sander Temme. The parent process, which typically runs as root, binds to a socket (usually port 80 or 443). It spawns children, which inherit the open file descriptor for the socket, and

问题 if i have a yield return in a lock statement does the lock get taken out on each yield (5 times in the example below) or only once for all the items in the list? Thanks private List<string> _data = new List<string>(){"1","2","3","4","5"}; private object _locker =new object(); public IEnumerable<string> GetData() { lock (_locker) { foreach (string s in _data) { yield return s; } } } 回答1: Edit: This answer was wrong, but I can't delete it as it was marked as correct. Please see @Lockszmith's

问题 I received the following deadlock log via "SHOW INNODB STATUS". Can someone care to explain why the transaction was aborted? It seems that Transaction 2 is holding the lock, but is also stuck requesting the same lock (except for the "waiting" part), which leads to a deadlock when Transaction 1 requires it as well. ===================================== 091205 6:25:01 INNODB MONITOR OUTPUT ===================================== Per second averages calculated from the last 39 seconds ----------

问题 I've got a List collection and I want to iterate over it in a multi threaded app. I need to protect it every time I iterate it since it could be changed and I don't want "collection was modified" exceptions when I do a foreach. What is the correct way to do this? Use lock every time I access or loop. I'm rather terrified of deadlocks. Maybe I'm just paranoid of using lock and shouldn't be. What do I need to know if I go this route to avoid deadlocks? Is lock fairly efficient? Use List<>