I'm developing a simple win32 application with two processes sharing memory through a file mapping. At a certain point in the second process, I want to check if the other process has already closed the handle associated to the file mapping.
Is there a Windows function to retrieve the number of handles associated to my shared memory???
Thanks in advance for any help...
There's nothing in the API to do that. If you want to know when the other process has finished its work, create a manual reset event with CreateEventEx, and have the other process set the event when its work is done. The first process can use one of the wait functions to query the status of the event.
Related
I am building a GUI (using C) which receives data to display from another application sending the data over a TCP socket. How do I do this using GTK (just a general overview of the approach I should take)? I have done a lot of searching and came across stuff about multithreading, GIOchannel etc. now I'm more confused than ever. There doesn't seem to be any conclusive articles or guides about how to actually achieve this.
There is basically one important rule:
You must call all gtk_* functions from the main thread.
If you update any widgets from another thread, you might get inconsistent results.
Of course, you don't want to wait for TCP data in that thread.
Therefore I would suggest you create a separate thread for doing the communication. In this thread you can wait for data and if you got anything that should affect what you show in your GUI, you can tell the main thread to do the required work.
A simple way to do this is to use g_idle_add() to enqueue a callback function. That callback function is then executed in context of main thread and can update your widgets.
The information what needs to be updated can be stored in some newly allocated memory that is passed to this callback where you have to free it afterwards.
System.Diagnostics.Process.Start(#C"\mydomain\mysubdomain\testdb\
app_DATA\DATAESCEL.exe);
This method has been called for insert excel sheets value into database. In main method I have write query fro save excel sheet values into database. Please help me how will I get return type value from above method?
This method returns a Process object.
Since you are creating another process from your main application, this process is main's child. However, communication between processes, yet trivial, may complicate your solution (you can search interprocess communication samples in the web).
If you simply want to know if your child process have succeeded, you can test its exit code (any value different from 0 indicates error).
Still, you could simply move this Excel structure to a DLL project and call it, say, as a thread. You would gain both in performance and simplicity.
I have a multithreaded WPF application that is using > 600 threads after is has been running for more than 8 hours. All but approximately 10 of these threads have a stack trace that is very similar to this:
Stack trace 1:
ntkrnlpa.exe!NtInitialUserProcessBuffer+0x7b
ntkrnlpa.exe!MiAddWorkingSetPage+0x174
ntkrnlpa.exe!MiAddWsleHash+0x12a
ntkrnlpa.exe!PopSystemButtonHandler+0x141
ntkrnlpa.exe!KiInterruptTemplate+0x62
ntdll.dll!KiFastSystemCallRet
ntdll.dll!ZwWaitForMultipleObjects+0xc
KERNEL32.dll!WaitForMultipleObjectsEx+0x12c
mscorwks.dll!WaitForMultipleObjectsEx_SO_TOLERANT+0x6f
mscorwks.dll!Thread::DoAppropriateAptStateWait+0x3c
mscorwks.dll!Thread::DoAppropriateWaitWorker+0x13c
mscorwks.dll!Thread::DoAppropriateWait+0x40
mscorwks.dll!WaitHandleNative::CorWaitOneNative+0x156
mscorlib.ni.dll+0x1f68af
mscorlib.ni.dll+0x1caa17
WindowsBase.ni.dll+0x24ac34
WindowsBase.ni.dll+0x2aeb1e
WindowsBase.ni.dll+0x9445d
WindowsBase.ni.dll+0x9267f
mscorwks.dll!JITutil_IsInstanceOfAny+0x106
mscorlib.ni.dll+0x1e842f
mscorwks.dll!CallDescrWorker+0x33
mscorwks.dll!CallDescrWorkerWithHandler+0xa3
mscorwks.dll!MethodDesc::CallDescr+0x19c
mscorwks.dll!MethodDesc::CallTargetWorker+0x1f
mscorwks.dll!MethodDescCallSite::Call+0x1a
mscorwks.dll!ExecuteCodeWithGuaranteedCleanupHelper+0x9f
mscorwks.dll!ReflectionInvocation::ExecuteCodeWithGuaranteedCleanup+0x10f
mscorlib.ni.dll+0x235677
mscorlib.ni.dll+0x2202a5
mscorlib.ni.dll+0x1e839b
mscorwks.dll!CallDescrWorker+0x33
mscorwks.dll!CallDescrWorkerWithHandler+0xa3
mscorwks.dll!DispatchCallBody+0x1e
mscorwks.dll!DispatchCallDebuggerWrapper+0x3d
mscorwks.dll!DispatchCallNoEH+0x51
mscorwks.dll!AddTimerCallback_Worker+0x66
mscorwks.dll!Thread::DoADCallBack+0x32a
mscorwks.dll!Thread::ShouldChangeAbortToUnload+0xe3
mscorwks.dll!Thread::ShouldChangeAbortToUnload+0x30a
mscorwks.dll!Thread::ShouldChangeAbortToUnload+0x33e
mscorwks.dll!ManagedThreadBase::ThreadPool+0x13
mscorwks.dll!AddTimerCallbackEx+0x83
mscorwks.dll!AddTimerCallback+0x10
mscorwks.dll!ThreadpoolMgr::AsyncTimerCallbackCompletion+0x64
mscorwks.dll!UnManagedPerAppDomainTPCount::DispatchWorkItem+0x9a
mscorwks.dll!ThreadpoolMgr::ExecuteWorkRequest+0xaf
mscorwks.dll!ThreadpoolMgr::WorkerThreadStart+0x20b
mscorwks.dll!Thread::intermediateThreadProc+0x49
KERNEL32.dll!BaseThreadStart+0x37
Stack Trace 2:
ntkrnlpa.exe!NtInitialUserProcessBuffer+0x7b
ntkrnlpa.exe!MiAddWorkingSetPage+0x174
ntkrnlpa.exe!MiAddWsleHash+0x12a
ntkrnlpa.exe!PopSystemButtonHandler+0x141
ntkrnlpa.exe!KiInterruptTemplate+0x62
ntdll.dll!KiFastSystemCallRet
ntdll.dll!ZwWaitForMultipleObjects+0xc
KERNEL32.dll!WaitForMultipleObjectsEx+0x12c
mscorwks.dll!WaitForMultipleObjectsEx_SO_TOLERANT+0x6f
mscorwks.dll!Thread::DoAppropriateAptStateWait+0x3c
mscorwks.dll!Thread::DoAppropriateWaitWorker+0x13c
mscorwks.dll!Thread::DoAppropriateWait+0x40
mscorwks.dll!WaitHandleNative::CorWaitOneNative+0x156
mscorlib.ni.dll+0x1f68af
mscorlib.ni.dll+0x1caa17
WindowsBase.ni.dll+0x24ac34
WindowsBase.ni.dll+0x2aeb1e
WindowsBase.ni.dll+0x9445d
WindowsBase.ni.dll+0x9267f
mscorwks.dll!JITutil_IsInstanceOfAny+0x106
mscorlib.ni.dll+0x1e842f
mscorwks.dll!CallDescrWorker+0x33
mscorwks.dll!CallDescrWorkerWithHandler+0xa3
mscorwks.dll!MethodDesc::CallDescr+0x19c
mscorwks.dll!MethodDesc::CallTargetWorker+0x1f
mscorwks.dll!MethodDescCallSite::Call+0x1a
mscorwks.dll!ExecuteCodeWithGuaranteedCleanupHelper+0x9f
mscorwks.dll!ReflectionInvocation::ExecuteCodeWithGuaranteedCleanup+0x10f
mscorlib.ni.dll+0x235677
mscorlib.ni.dll+0x2202a5
mscorlib.ni.dll+0x1e839b
mscorwks.dll!CallDescrWorker+0x33
mscorwks.dll!CallDescrWorkerWithHandler+0xa3
mscorwks.dll!DispatchCallBody+0x1e
mscorwks.dll!DispatchCallDebuggerWrapper+0x3d
mscorwks.dll!DispatchCallNoEH+0x51
mscorwks.dll!AddTimerCallback_Worker+0x66
mscorwks.dll!Thread::DoADCallBack+0x32a
mscorwks.dll!Thread::ShouldChangeAbortToUnload+0xe3
mscorwks.dll!Thread::ShouldChangeAbortToUnload+0x30a
mscorwks.dll!Thread::ShouldChangeAbortToUnload+0x33e
mscorwks.dll!ManagedThreadBase::ThreadPool+0x13
mscorwks.dll!AddTimerCallbackEx+0x83
mscorwks.dll!AddTimerCallback+0x10
mscorwks.dll!ThreadpoolMgr::AsyncTimerCallbackCompletion+0x64
mscorwks.dll!UnManagedPerAppDomainTPCount::DispatchWorkItem+0x9a
mscorwks.dll!ThreadpoolMgr::ExecuteWorkRequest+0xaf
mscorwks.dll!ThreadpoolMgr::WorkerThreadStart+0x20b
mscorwks.dll!Thread::intermediateThreadProc+0x49
KERNEL32.dll!BaseThreadStart+0x37
Application uses System.Threading.Timer to periodically poll for data from several webservices using a WCF client proxy and at any giving time, could be making about 20 of these requests at the same time. Each call to a webservice instantiates a new proxy instance but the client is always closed when a response is received from the webservice.
Application also manipulates with bitmaps for a GIS and this is also done on a periodic interval. No where in code am I explicitly creating threads besides localized usage of the Timer class to poll for data periodically. The GIS does
use the BackgroundWorker but they do limit the thread count.
Anyone have an idea on what is spawning these new threads and why they are not being disposed?
TIA.
Yeah, looks like something you shouldn't ignore. They are the threadpool thread that the Timer class uses to make the callback. They are deadlocked, looks like they are waiting for a method call that's marshaled by COM to complete. There should be another thread in your program, one of the other 10 on which you created the GIS object. That thread is not pumping a message loop, a hard requirement for an STA thread that creates single apartment threaded COM components. Or it is stuck itself, not re-entering the message loop. Getting a managed stack trace ought to make it easier to see where the thread is stuck.
Trying to use threads on a COM object that explicitly doesn't support them (very few do) is pointless. Be sure to create the GIS object on your program's main UI thread. And use a DispatcherTimer. Creating your own STA thread that pumps a message loop can be a solution when the GIS component is taking too much of a hit on your user interface.
Problem was not GIS related but was due to System.Threading.Timer call backs queuing up as they were being called faster than they could be actioned. Problem was further compounded by the fact that timer call back was doing a Dispatcher.Invoke to the main user interface thread to refresh data grids. Dispatcher.Invoke was blocking when main user interface was busy, say when user was panning and zooming on map, and before timer call back got a chance to complete it was invoked again.
Fixed problem by temporarily stopping timer when it starts executing the call back and restarting it again after call back is complete. Also, instead of doing a Dispatcher.Invoke to get my grids updated, I changed it to a Dispatcher.BeginInvoke to avoid blocking.
This is a question which follows on from my previously answered question here
At first I assumed I had a problem with the way I was creating my events due to the handles for OpenEvent returning NULL, I have managed to find the real cause however I am not sure how to go about it.
Basically I use Visual Studio to launch both Process A and B at the same time, in the past my OpenEvent handle wouldn't work due to Process A looking for the address of the event a fraction of a second before Process B had time to make it.
My solution was to simply allow Process B to run before Process A, fixing the error.
The problem I have now is that Process B now reads events from Process A and as you expect it too returns a null handle when trying to open the events from Process A.
I am creating the events in WM_CREATE message of both processes, furthermore I also create a thread at the same time to open/read/act upon the events.
It seems if I run them at the same time they don't get chance to see each other, alternatively if I run one before the other one of them misses out and can't open a Handle.
Can anyone suggest a solution?
Thanks.
Just replace OpenEvent with CreateEvent. CreateEvent will open an Event instead of creating a new one it finds an existing event with the name passed to CreateEvent.
I have a Windows service (under WinXP SP2), running under the LocalSystem account, that launches processes using CreateProcessWithLogonW. In order to clean up child processes, I'm trying to use a job object and TerminateJobObject.
MSDN states that the job handle must have JOB_OBJECT_ASSIGN_PROCESS access right, which it has since it's created via CreateJobObject. The process handle must have PROCESS_SET_QUOTA and PROCESS_TERMINATE rights. I think it has them since TerminateProcess and SetProcessWorkingSetSize both return with no error.
Though, AssignProcessToJobObject fails with errno 5 (Access denied). Everything works fine if I replace CreateProcessWithLogonW with a simple CreateProcess.
Am I missing something or is what I'm trying to do impossible ?
Edit: It seems that svchost.exe, which actually creates the process when CreateProcessWithLogonW is used, already assigns the process to an anonymous job. The CREATE_CREAKAWAY_FROM_JOB flag is ignored by this function. So the real question is: is there a way to prevent svnhost from assigning the process to a job ?
From Jeff Lawson on MSDN:
Interactions with Win32 Job Objects
CreateProcessWithLogonW executes the
new process as a child of the
Secondary Logon service, which has the
outcome of making the process escape
any Job Object membership/restrictions
even if the Job Object did not allow
breakaway.
Furthermore, the Secondary
Logon service automatically creates
its own new Job Object and assigns the
new process into it. As such, it is
not possible for the caller to
explicitly assign the new process to
any other Job Object (since a process
may only be assigned to one Job
Object, and can never be removed from
a Job Object once it has been assigned
to one).
Does each new process need a different logon? Otherwise, you could create a single process with the new logon and have it spawn new process using CreateProcess that could then be associated with a Job Object.
we can enable privilege and use CreateProcessAsUserW instead