I'm a hobbyist programmer and have written a small application using Python3 and Gtk3.
It has two threads in it. One is a simple clock showing current time and updating the GUI every minute. The other is a countdown timer which can be started and stopped (the thread is killed with a flag on pause, and a new thread created on start). Both threads are daemons and neither interacts with the other.
It is working perfectly in linux.
In Windows it freezes / locks up, even when I haven't started the timer (i.e. only the clock thread is active). Windoze complains: "Python.exe is not responding".
My initial question is just whether it is safe to use threads in Windows. Or perhaps it is not a good idea to use GTK3?
Has anyone else experienced something like this?
Related
I have a new Win10 laptop. I've installed lots of software, including a 25-year-old Codewright editor that I've customized up the wazoo, and that I've been installing on all my machines for, well, 25 years. After working for a few days, it suddenly stopped, and reinstalling it didn't fix it. On startup, it puts up a small splash window, and normally opens the main window a half a second later (that took more than 5 seconds 25 years ago). It's not using any CPU, and there's nothing I can do but kill the process.
In the past, I've occasionally got my system into a state where Codewright would hang on loading, due to some other program that hadn't terminated correctly, and it was unfrozen by killing off that other process. So that's reason to believe that Codewright is waiting at some global lock which some other malfunctioning software is holding. So I have two questions:
Does this ring a bell? Is there some known failure mode where a program putting up a splash window then switching to another window can be prevented by something else going on the system?
Is there a way to diagnose this, perhaps by finding out what system call it's hanging inside? I tried dtrace.exe, started Codewright, and then stopped tracing, and it produced a 3GB XML file, which is quite a haystack. There's a way to filter it by PID, but since this is a startup problem, I have no idea what the PID will be. Is there a better tool for doing this, or some more appropriate dtrace feature that I missed?
The comment about using the Task Manager to create a dump file actually led me to notice that there is an Analyze Wait Chain function there that I had never seen before, since I haven't used Task Manager much since I switched from Win7. This gave me exactly the answer I wanted. My editor was waiting for something that was being held by some NVIDIA GeForce Experience module. Since I don't use that, I uninstalled it, and I'm back up and running. Thanks for the tip.
I'm developing multi-threading application on mac os. I'm faced with next problem: when i'm trying to debug with xcode-cocoa application(NOTE: console application doesn't have same problem), my threads are returning with errors in next calls: kevent(), semaphore_wait(), semaphore_timedwait() with EINTR (for kevent) and KERN_ABORTED (for semaphore_*). I think this is due to lldb work.
The problem is: i can't debug my application as i'm crashing after receiving such events. If i will do their handling(just make recall of same function) then my application is working very strange. Anyway I can't(I can, but it's very ugly) make good handling for such situation when my semaphore_timedwait() interrupting as i should "remember" time before i have gone timedwait() to make new timedwait() correct.
So, solution for my problems would be if I could disable for current thread "interrupting" - ability to be interrupted from another thread\process, that my functions will not return if lldb will send some signal. Is it possible on mac os?
Few notes:
In some debugegrs (I know gdb supports that) you can say whether all threads or only the one are stopped on the breakpoint.
Generally, you should be ready in your code a signal comes even if it is more work.
In multithreading application you can consider blocking the signals in most (helper) threads, so the signals shall be handled in a thread which is ready for that. See pthread_sigmask().
is it possible to fire up an event at a specified time interval in BlackBerry? I'm looking for something similar to AlarmManager class in Android (if anyone is familiar with it).
The goal is to is to run some code, even when the application is not in foreground and without it gaining foreground "focus". Preferably it should be possible to fire the event even if the app was killed by system or by phone reboot (I do not know the details about killing apps at this OS, I'm beginning development now).
I would prefer not to write a background process for this task as it is going to be fired every few hours (I think it would be a waste of battery to use a background task for a simple alarm-like event).
I've looked around a lot, but I cannot find any satisfying solution.
cheers,
kajman
The Timer and TimerTask classes are useful for running a task on a schedule. Take a look at the APIs here:
http://www.blackberry.com/developers/docs/7.0.0api/java/util/Timer.html
The Timer will create its own Thread and sleep until it has a task to run. It would involve having a background task running but it wouldn't be using an CPU or battery if it is just waiting.
If you don't want a Thread running all of the time you can use the ApplicationManager class to schedule your application to start later.
You can also configure your app to run on start up. The OS generally won't kill your apps unless you have a coding error. RIM refers to this as the Always-On Experience in their Super App document:
http://docs.blackberry.com/en/developers/deliverables/23567/Always_on_1380986_11.jsp#Keeping_the_app_running_1381022_11
If an app is brought to the background what happens to the UI Thread which was running this app?
Will it sleep or get killed?
When the app is back to foreground will the same thread be notified or a new thread will created and associated with the app instance?
I don't know specifically, but you should always program with the possibility that your Activity may be killed at any time that it is not in the foreground. Whether that involves killing the thread every time it enters the background, or causing the thread to sleep and then killing it if the Activity is killed, I don't know. In any case, you must assume it can and will happen, and program accordingly.
It depends on the memory situation. When your application goes into the background, it generally stays running initially. Android does not sleep your thread. It is up to you to stop updating your UI and performing calculations in on onPause.
However in low memory situations Android might kill application when it's the background (especially if you haven't been nice and are using up a load of resources). For this reason you should always save any persistant data in onPause.
When Mac OS X goes to sleep, due to closing a laptop or selecting "Sleep" from the Apple menu, how does it suspend an executing process?
I suppose non-windowed processes are simply suspended at an arbitrary point of execution. Is that also true for Cocoa apps, or does the OS wait until control returns to the run loop dispatcher, and goes to sleep in a "known" location? Does any modern OS do that, or is it usually safe enough to simply suspend an app no matter what it is doing?
I'm curious, because allowing sleep to occur at any moment means, from the app's perspective, the system clock could suddenly leap forward by a significant amount. That's a possibility I don't usually consider while coding.
Your app is interrupted exactly where it is that moment if the CPU is actually currently executing code of your app. Your app constantly gets execution time by the task scheduler, that decides which app gets CPU time, on which core, and for how long. Once the system really goes to sleep, the scheduler simply gives no time to your app any longer, thus it will stop execution wherever it is at that moment, which can happen pretty much everywhere. However, the kernel must be in a clean state. That means if you just made a call into the kernel (many libC functions do) and this call is not at some safe-point (e.g. sleeping, waiting for a condition to become true, etc.) or possibly holding critical kernel locks (e.g. funnels), the kernel may suspend sleep till this call returns back to user space or execution reaches such a safe-point before it finally cancels your app from the task scheduler.
You can open a kernel port and register for sleep/wake-up events. In that case, your app will receive an event, when the system wants to go to sleep. You have several possibilities. One is to reply to it, that the system may progress. Another one is to suspend sleep; however, Apple says certain events can be suspended at most 30 seconds, after that, the system will just continue, whether your app likes it or not. And finally, you can cancel it; though not all events can be canceled. If the system already decided it will go to sleep, you can only suspend this by at most 30 seconds or allow it at once, you cannot cancel it. However, you can also listen to an event, where the system asks apps, if it is okay to go to sleep now and there you can reply "no", causing a sleep to be canceled.
The difference between "Is it okay to sleep" and "I'm planing on going to sleep" is: The first one is sent if the power saving settings are applied, that is, if the user has not moved the mouse or typed anything for the time configured there. In that case the system will just ask, if sleep is okay. An app like Apple's DVD Player will say "no", because most likely the user watches a DVD and thus doesn't interact with the computer, still no reason to go to sleep. OTOH, if the user closes his Mac Book, apps are not asked, the system will go to sleep for sure and just informs apps, that have now up to 30 seconds to react to it.
Wake-up events can also be quite interesting to catch. E.g. if your system wakes up, open files might be inaccessible (an external drive has been unplugged) or network sockets won't work any longer (network has changed). So you may re-init certain app parts before using them and running into errors that are more or less expected.
Apple's page regarding catching these events.
It depends on your app.
If you are interacting with external systems (think networking or doing something over usb/firewire,etc) then it might be affected. An application running on OSX gets to run for a limited time ( max 10ms ) , after which it is interrupted by the kernel which schedules a new process from the process queue to run on the CPU. This is transparent for the application , which "thinks" that it runs all the time on the CPU. Thus , a transition to sleep is no different - apart from the time jumping ahead.
If you need to be aware that there was a transition to sleep mode please refer to this tech note which details how to receive notifications about the state change : Registering and unregistering for sleep and wake notifications
I believe it will just suspend all apps wherever they happen to be.
Remember, this happens all the time anyway. Applications are constantly suspended and resumed due to context switching. So, really, the clock could jump between any 2 instructions in your app, though usually not in a noticable/significant way.
If the OS waited for the app to return to some main loop you could run into situations where applications cause the sleep to hang. If they're doing a lot of work and not returning to the run loop dispatcher they would prevent the machine from going to sleep. That wouldn't be very good. :)
And if you set the time it also appears to leap forward to the running programs. Nothing special either.
Check out this Wikipedia article. Cavver is correct in stating that things like network connections may time out, and thus those services may be interrupted.