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How to get all running thread current status
Hi,
My mulithread application hangs randomly. I don't know which thread and where it hangs. How to get current status(current call stack) of all running threads.
How to find dead lock in multithread application.
OR any other way to find the application hangs.
My mulithread application hangs randomly. I don't know which thread and where it hangs. How to get current status(current call stack) of all running threads.
How to find dead lock in multithread application.
OR any other way to find the application hangs.
I would be interested to hear about approaches for this. I have successfully used good ol' logging in the past, but it is a bit cumbersome. I'll explain:
First of all, you must synchronize access to the log file. I created a pure virtual class called ILock with three methods: Lock(), Unlock() and Name(). Then I created a new class that inherits from ILock and implements Lock() and Unlock() via a mutex (it is multi-threaded, multi-process), but if you don't cross process boundaries, you could code a class that uses a semaphore or a critical section (being the latter the fastest).
Once synchronized, you log every attempt to acquire a synchronization lock, namely mutexes, critical sections, events, semaphores, waiting on threads or processes, etc; you also log if you were successful in acquiring the said lock, and you also log where you release the locks. Finally, every line in the log file needs to include the thread ID (and the process ID if multi-process).
With the above, a well behaved program will have log pairs. The first item in the pair is two lines, while the second item is one line:
Any thread not releasing a lock is a potential problem that could be reflected in another thread. The thread hanging would have the first half of the first item of the expected pair, but nothing else.
If the code above produces something like:
Then you may end up with a deadlock. Maybe your code acquires locks for a long time, so you need to judge the time to consider it a deadlock.
First of all, you must synchronize access to the log file. I created a pure virtual class called ILock with three methods: Lock(), Unlock() and Name(). Then I created a new class that inherits from ILock and implements Lock() and Unlock() via a mutex (it is multi-threaded, multi-process), but if you don't cross process boundaries, you could code a class that uses a semaphore or a critical section (being the latter the fastest).
Once synchronized, you log every attempt to acquire a synchronization lock, namely mutexes, critical sections, events, semaphores, waiting on threads or processes, etc; you also log if you were successful in acquiring the said lock, and you also log where you release the locks. Finally, every line in the log file needs to include the thread ID (and the process ID if multi-process).
With the above, a well behaved program will have log pairs. The first item in the pair is two lines, while the second item is one line:
-Thread ID 0xXYZ: Trying to acquire lock "MyMutexLock". -Thread ID 0xXYZ: Acquired lock "MyMutexLock". - ..... -Thread ID 0xXYZ: Releasing lock "MyMutexLock". |
Any thread not releasing a lock is a potential problem that could be reflected in another thread. The thread hanging would have the first half of the first item of the expected pair, but nothing else.
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If the code above produces something like:
-Thread ID 0xXYZ: Trying to acquire lock "MyMutexLock". -Thread ID 0xXYZ: Acquired lock "MyMutexLock". - ... -Thread ID 0xABC: Trying to acquire lock "MyMutexLock". //The following line may or may not show up. If it doesn't, thread ID 0xABC will deadlock. -Thread ID 0xXYZ: Releasing lock "MyMutexLock". |
Then you may end up with a deadlock. Maybe your code acquires locks for a long time, so you need to judge the time to consider it a deadlock.
By 'hang' i understand that your program doesn't crash, just stops doing anything?
You can try the Sleepy profiler, (http://sleepy.sourceforge.net/), a small program that can tell you what function is currently running in a windows program (if the program has debug information included)
Or doesn't your IDE have a debugger? Sometimes, when you pause your program execution, it can show you in which wait section the program is, and the call stack for each thread
You can try the Sleepy profiler, (http://sleepy.sourceforge.net/), a small program that can tell you what function is currently running in a windows program (if the program has debug information included)
Or doesn't your IDE have a debugger? Sometimes, when you pause your program execution, it can show you in which wait section the program is, and the call stack for each thread
First I would make sure that you are actually seeing a lock, when you open task manager do you see that your process isn't doing anything? I use Process Explorer: http://technet.microsoft.com/en-us/sysinternals/bb896653 to see what threads are pinning the CPU if any.
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