I want to write a program that can not close it
In other words, they can not kill process .
The solution of the process of closure for less than the other way is to do a good job
I have another solution?
Assuming Linux, this is not quite possible from userspace because there are signals like
SIGKILL that cannot be ignored or handled.
If you have access to kernel, than you could write a kernel moudule which puts the current process in state TASK_UNINTERRUPTIBLE and thus no one could kill it.
please specify your question in detail.
i think you have facing error on previous activity is onResume();
you have to on resume method for removing this error.
in onResume() method you can call finish(); method for stop activity.
Related
I'm new to threading, so there are a few things I'm trying to grasp correctly.
I have a windows form application that uses threading to keep my UI responsive while some server shenanigans are going on.
My question is: when I quit my application, what happens to ongoing threads? Will they run to completion or will the abruptly be interrupted?
If they are interrupted, what can I do to make sure they at least don't get interrupted in such a way that would corrupt data on my server (force them to run to a safe place in the code where I know it's ok to interrupt the execution)
You will want to keep a reference of said threads, and call .Abort() on them when you want to terminate. Then you put your thread's code in a try/catch block and handle ThreadAbortException's. This will let you clean up what you are doing and terminate the thread cleanly at your own pace. In the main thread, after you called .Abort(), you just wait until the thread is no longer running (by polling the .IsAlive property of the Thread object) and close your application afterwards.
A thread needs a process to run in. The process won't be able to terminate if you don't terminate all the non-background threads you have started. Threads marked as background thread will be aborted.
So, the behavior is entirely up to your implementation. If you want to close the application, you could wait for all threads to terminate by themself, you could set an event to ask them to terminate and wait or you could just kill the threads.
The UI thread will terminate by itself because it runs a messageloop that stops when requested by the operating system, also see wikipedia and this answer.
I wonder if process could stay in blocked state even if there is not any other process that want to run.
Theroticaly i guess the answer is yes ,but in practically it is not .. i'm right ?
Simple example: your process X is waiting for some IO to show on some socket indiscriminately.
In other words: you make some sort of read() call without any kind of timeout. That process will just sit there, and do nothing. No matter what other processes in that system do.
I am facing an issue in our C based application where one of VxWorks TASK(say Task1) got crashed due to some unknown reasons. The crashed task had locked a mutual exclusion semaphore(say semA).
Now the next TASK2 is waiting on semA to get Unlocked. Since semA is locked by a crashed TASK, TASK2 will be waiting infinitely to grab semA. This has broken application functionality.
We can not provide a timeout to lock semA in TASK2 becuase semA is protecting a send routing that is sending data over sockets. Providing a timeout will result in failure in message communication.
After googling I have found ROBUST mutex for LINUX for such problem, but our platform is VxWorks(version 5.5.1).
So can somebody tell me the way by which we can handle this problem in VxWorks?
I have tried a below mentioned solution nut not sure how safe it is to do so.
1) TASK2 will wait on semA for a particular timout
2) if failed check the state of previous task that had locked the semA
3 if TASK1 state is SUSPENDED, TASK 2 will call semDelete on semA and than recreate it.
4) if TASK1 is not in SUSPENDED state, keep on waiting to grab semA.
I have test this code as prototype and is working fine. I am not sure about how good is to implement such solution where we recreate semaphore and what will be the possible risks imposed.
Please let me know your inputs.
Thanks
I think your prototyped solution is not anymore risky than having code (Task1) that crashes for unknown reasons.
If I were to work on your problem, I would first try really hard to find out why Task1 is crashing. If I were unable to figure out the root cause, I would then go to implement your proposed solution. That is, I would query the state of Task2 after a certain amount of time, and then recreate the semaphore.
I must say, that even if you implement your work around of recreating the semaphore, then you still have a crashed task which consumes resources. If this problem persists, then eventually the whole system will stop working.
In the end the correct and only way to fix this problem is to fix the crash in task1. You should be able to get a stack trace to where it crashed and fix it.
I second the previous answers: finding the cause why Task1 crashes is better than implementing a workaround.
Can you post the messages written by VxWorks of the crashed Task1?
One of the first things I try if a task crashes for no good reason is to increase its stack size (let's say double it). If the task runs fine your stack size is too small. Also try to increase the stack size of the task(s) you've modified lately!
If it is a stack problem it isn't neccessarily Task1 which is to blame...
Does anyone know how one can automatically reply to messages with status MSGW that block a job on an IBM i-series (AS/400)?
I'm using the jt400/jtopen library to access a program on an AS/400 from Java. I'm using the com.ibm.as400.access.ProgramCall class, which works fine, unless the program fails for some reason. As with almost any program, failures will happen sometimes, but unfortunately, in this case, it does not result in a status message or an exception. Instead, the calling thread just hangs. What's worse, any call to the AS/400 to get information on the Job (another class in jt400 that mostly does what you would expect) backing the queue will hang as well.
I could of course monitor the thread in which the call runs and simply kill it after waiting for a while, but that's a last resort. Getting an error message back from the system would be nice.
You could try execute this command before invoke your pcml with com.ibm.as400.access.CommandCall.run() method:
CHGJOB INQMSGRPY(*DFT)
It sets 'C' as default answer for all messages.
but you should ensure you have log of the messages in order to know the problem which generates this message
Regards,
I don't believe Java can directly trap errors that occur on the other side of that API. What I've done is to 'harden' the RPG (IBM i side) program so that it monitors for errors rather than let the default error handler get them. When an error occurs, the RPG program gracefully terminates and passes back an error code or even the entire message back to the Java application.
I've found that you can use the timeout mechanism of ExecutorService to interrupt a ProgramCall in MSGW.
You must discard the AS400 object afterwards, and the server job is still in MSGW, but at least you can continue on the Javaside.
(You need to use a separate AS400 object if you want to investigate on the hanging job.)
Scenario:
I have a Distributed-objects-based IPC between a mac application and a launchd daemon (written with Foundation classes). Since I had issues before regarding asynchronous messaging (e.g. I have a registerClient: on the server's root object and whenever there's an event the server's root object notifies / calls a method in the client's proxy object), I did long-polling which meant that the client "harvests" lists of events / notifications from the daemon. This "harvest" is done through a server object method call, which then returns an NSArray instance.
It works pretty well, until for a few seconds, the server object's process (launched thru launchd) starts being labeled red with the "(Not responding)" tag beside it (inside Activity Monitor). Like I said, functionally, it works well, but we just want to get rid of this "Not responding" label.
How can I prevent this "Not responding" tag?
FYI, I already did launchd-based processes before and this is the first time I did long-polling. Also, I tried NSSocketPortNameServer-based connections and also NSSocketPort-based ones. They didn't have this problem. Locking wasn't also an issue 'coz the locks used were only NSCondition's and we logged and debugged the program and it seems like the only locking "issue" is on the harvesting part, which actually, functionally works. Also, client-process is written in PyObjC while server process was written using ObjC.
Thanks in advance.
Sample the process to find out what it's doing or waiting on.
Peter's correct in the approach, though you may be able to figure it out through simple inspection. "Not responding" means that you're not processing events on your event queue for at least 5 seconds (used to be 2 seconds, but they upped it in 10.4). For a UI process, this would create a spinning wait cursor, but for a non-UI process, you're not seeing the effects as easily.
If this is a runloop-based program, it means you're probably doing something with a blocking (synchronous) operation that should be done with the run loop and a callback (async). Alternately, you need a second thread to process your blocking operations so your mainthread can continue to respond to events.
My problem was actually the call for getting a process's PID using the signature FNDR... that part caused the "Not responding" error and it never was the locks or the long-polling part. Sorry about this guys. But thank God I already found the answer.