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• How to use pthread_atfork() and pthread_once() to reinitialize mutexes in child processes

  - by Blair Zajac

  We have a C++ shared library that uses ZeroC's Ice library for RPC and unless we shut down Ice's runtime, we've observed child processes hanging on random mutexes. The Ice runtime starts threads, has many internal mutexes and keeps open file descriptors to servers. Additionally, we have a few of mutexes of our own to protect our internal state. Our shared library is used by hundreds of internal applications so we don't have control over when the process calls fork(), so we need a way to safely shutdown Ice and lock our mutexes while the process forks. Reading the POSIX standard on pthread_atfork() on handling mutexes and internal state: Alternatively, some libraries might have been able to supply just a child routine that reinitializes the mutexes in the library and all associated states to some known value (for example, what it was when the image was originally executed). This approach is not possible, though, because implementations are allowed to fail *_init() and *_destroy() calls for mutexes and locks if the mutex or lock is still locked. In this case, the child routine is not able to reinitialize the mutexes and locks. On Linux, the this test C program returns EPERM from pthread_mutex_unlock() in the child pthread_atfork() handler. Linux requires adding _NP to the PTHREAD_MUTEX_ERRORCHECK macro for it to compile. This program is linked from this good thread. Given that it's technically not safe or legal to unlock or destroy a mutex in the child, I'm thinking it's better to have pointers to mutexes and then have the child make new pthread_mutex_t on the heap and leave the parent's mutexes alone, thereby having a small memory leak. The only issue is how to reinitialize the state of the library and I'm thinking of reseting a pthread_once_t. Maybe because POSIX has an initializer for pthread_once_t that it can be reset to its initial state. #include <pthread.h> #include <stdlib.h> #include <string.h> static pthread_once_t once_control = PTHREAD_ONCE_INIT; static pthread_mutex_t *mutex_ptr = 0; static void setup_new_mutex() { mutex_ptr = malloc(sizeof(*mutex_ptr)); pthread_mutex_init(mutex_ptr, 0); } static void prepare() { pthread_mutex_lock(mutex_ptr); } static void parent() { pthread_mutex_unlock(mutex_ptr); } static void child() { // Reset the once control. pthread_once_t once = PTHREAD_ONCE_INIT; memcpy(&once_control, &once, sizeof(once_control)); setup_new_mutex(); } static void init() { setup_new_mutex(); pthread_atfork(&prepare, &parent, &child); } int my_library_call(int arg) { pthread_once(&once_control, &init); pthread_mutex_lock(mutex_ptr); // Do something here that requires the lock. int result = 2*arg; pthread_mutex_unlock(mutex_ptr); return result; } In the above sample in the child() I only reset the pthread_once_t by making a copy of a fresh pthread_once_t initialized with PTHREAD_ONCE_INIT. A new pthread_mutex_t is only created when the library function is invoked in the child process. This is hacky but maybe the best way of dealing with this skirting the standards. If the pthread_once_t contains a mutex then the system must have a way of initializing it from its PTHREAD_ONCE_INIT state. If it contains a pointer to a mutex allocated on the heap than it'll be forced to allocate a new one and set the address in the pthread_once_t. I'm hoping it doesn't use the address of the pthread_once_t for anything special which would defeat this. Searching comp.programming.threads group for pthread_atfork() shows a lot of good discussion and how little the POSIX standards really provides to solve this problem. There's also the issue that one should only call async-signal-safe functions from pthread_atfork() handlers, and it appears the most important one is the child handler, where only a memcpy() is done. Does this work? Is there a better way of dealing with the requirements of our shared library?

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• Java ExecutorService java heap space ptoblems

  - by Sergey Aganezov jr

  I have a little bit of a problem in a multitasking java department. I have a class, called public class ThreadWorker implements Runnable { //some code in here public void run(){ // invokes some recursion method in the ThreadWorker itself, // which will stop eventually { } all in all, pretty simple "worker" that can work on it's on. To work with threads I'm using public static int THREAD_NUMBER = 4; public static ExecutorServide es = Executors.newFixedThreadPool(THREAD_NUMBER); adding instances of ThreadWroker class happens here: public void recursiveMethod(Arraylist<Integers> elements, MyClass data){ if (elements.size() == 0 && data.qualifies()){ ThreadWorker tw = new ThreadWorker(data); es.execute(tw); return; } for (int i=0; i< elements.size(); i++){ // some code to prevent my problem MyClass data1 = new MyClass(data); MyClass data2 = new MyClass(data); ArrayList<Integer> newElements = (ArrayList<Integer>)elements.clone(); data1.update(elements.get(i)); data2.update(-1 * elements.get(i)); newElements.remove(i); recursiveMethod(newElements, data1); recursiveMethod(newElements, data2); { } and the problem is that the depth of the recursion tree is quite big, so as it's width, so a lot of ThreadWorkers are added to the ExecutorService, so after some time on the big input a get Exception in thread "pool-1-thread-2" java.lang.OutOfMemoryError: Java heap space which is caused, as I think because of a ginormous number of ThreadWorkers i'm adding to ExecutorSirvice to be executed, so it runs out of memory. Every ThreadWorker takes about 40 Mb of RAM for all it needs. Is there a method to get how many threads (instances of classes implementing runnable interface) have been added to ExecutorService? So I can add it in the shown above code (int the " // some code to prevent my problem"), as while ("number of threads in the ExecutorService" > 10){ Thread.sleep(10000); } so I won't go to deep or to broad with my recursion and prevent those exception-throwing situations. Sincerely, Sergey Aganezov jr.

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• How to create a run loop that only listens to performSelector:onThread: and GUI events?

  - by Paperflyer

  I want to create a separate thread that runs its own window. Frankly, the documentation does not make sense to me. So I create an NSThread with a main function. I start the thread, create an NSAutoreleasePool, and run the run loop: // Global: BOOL shouldKeepRunning = YES; - (void)threadMain { NSAutoreleasePool *pool = [NSAutoreleasePool new]; // Load a nib file, set up its controllers etc. while (shouldKeepRunning) { NSAutoreleasePool *loopPool = [NSAutoreleasePool new]; [[NSRunLoop currentRunLoop] runUntilDate:[NSDate distantFuture]]; [loopPool drain]; } [pool drain]; } But since there is no registered port or observer, runUntilDate: exits immediately and CPU utilization goes to 100%. All thread communication is handled by calls to performSelector:onThread:withObject:waitUntilDone:. Clearly, I am not using the API correctly. So, what am I doing wrong?

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• Java fatal error, don't know what it means

  - by Thomas King

  It happens at the same place in my code (albeit not the first time the method is executed) but I can't make head or tail of what is wrong. (Doubly so as it's code for a robot). Be most appreciative if someone can give me an idea of what kind of problem it is. I assume it's to do with threading (multi-threaded app) but I don't really know what?!? Worried as deadline for uni project is looming!!! The message: # A fatal error has been detected by the Java Runtime Environment: # SIGSEGV (0xb) at pc=0xb70f0ca7, pid=5065, tid=2145643376 # JRE version: 6.0_15-b03 Java VM: Java HotSpot(TM) Server VM (14.1-b02 mixed mode linux-x86 ) Problematic frame: V [libjvm.so+0x4c9ca7] # An error report file with more information is saved as: /home/thomas/workspace/sir13/hs_err_pid5065.log # If you would like to submit a bug report, please visit: http://java.sun.com/webapps/bugreport/crash.jsp # The log: # A fatal error has been detected by the Java Runtime Environment: # SIGSEGV (0xb) at pc=0xb70f0ca7, pid=5065, tid=2145643376 # JRE version: 6.0_15-b03 Java VM: Java HotSpot(TM) Server VM (14.1-b02 mixed mode linux-x86 ) Problematic frame: V [libjvm.so+0x4c9ca7] # If you would like to submit a bug report, please visit: http://java.sun.com/webapps/bugreport/crash.jsp # --------------- T H R E A D --------------- Current thread (0x0904ec00): JavaThread "CompilerThread1" daemon [_thread_in_native, id=5078, stack(0x7fdbe000,0x7fe3f000)] siginfo:si_signo=SIGSEGV: si_errno=0, si_code=1 (SEGV_MAPERR), si_addr=0x00000004 Registers: EAX=0x00000000, EBX=0xb733d720, ECX=0x000003b4, EDX=0x00000000 ESP=0x7fe3bf30, EBP=0x7fe3bf78, ESI=0x7fe3c250, EDI=0x7e9a7790 EIP=0xb70f0ca7, CR2=0x00000004, EFLAGS=0x00010283 Top of Stack: (sp=0x7fe3bf30) 0x7fe3bf30: 00020008 7ec8de5c 7fe3c250 00000000 0x7fe3bf40: 7f610451 00001803 7e9a7790 000003f5 0x7fe3bf50: 7e920030 7f239910 7f23b349 7f23b348 0x7fe3bf60: 7f550e35 7fe3c250 0000021b b733d720 0x7fe3bf70: 000003bc 7f23db10 7fe3bfc8 b70f0997 0x7fe3bf80: 7fe3c240 7f23db10 00000000 00000002 0x7fe3bf90: 00000000 7fe3c1b0 00000000 00000000 0x7fe3bfa0: 00004000 00000020 7ec88870 00000002 Instructions: (pc=0xb70f0ca7) 0xb70f0c97: 7d 08 8b 87 c8 02 00 00 89 c7 8b 45 c4 8b 14 87 0xb70f0ca7: 8b 42 04 8b 00 85 c0 75 22 8b 4e 04 8b 52 1c 39 Stack: [0x7fdbe000,0x7fe3f000], sp=0x7fe3bf30, free space=503k Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code) V [libjvm.so+0x4c9ca7] V [libjvm.so+0x4c9997] V [libjvm.so+0x4c6e23] V [libjvm.so+0x25b75f] V [libjvm.so+0x2585df] V [libjvm.so+0x1f2c2f] V [libjvm.so+0x260ceb] V [libjvm.so+0x260609] V [libjvm.so+0x617286] V [libjvm.so+0x6108fe] V [libjvm.so+0x531c4e] C [libpthread.so.0+0x580e] Current CompileTask: C2:133 ! BehaviourLeftUnexplored.action()V (326 bytes) --------------- P R O C E S S --------------- Java Threads: ( = current thread ) 0x08fb5400 JavaThread "DestroyJavaVM" [_thread_blocked, id=5066, stack(0xb6bb0000,0xb6c01000)] 0x09213c00 JavaThread "Thread-4" [_thread_blocked, id=5085, stack(0x7eeaf000,0x7ef00000)] 0x09212c00 JavaThread "Thread-3" [_thread_in_Java, id=5084, stack(0x7f863000,0x7f8b4000)] 0x09206800 JavaThread "AWT-XAWT" daemon [_thread_in_native, id=5083, stack(0x7f8b4000,0x7f905000)] 0x091b7400 JavaThread "Java2D Disposer" daemon [_thread_blocked, id=5082, stack(0x7f93e000,0x7f98f000)] 0x09163c00 JavaThread "Thread-0" [_thread_in_native, id=5081, stack(0x7fc87000,0x7fcd8000)] 0x09050c00 JavaThread "Low Memory Detector" daemon [_thread_blocked, id=5079, stack(0x7fd6d000,0x7fdbe000)] =0x0904ec00 JavaThread "CompilerThread1" daemon [_thread_in_native, id=5078, stack(0x7fdbe000,0x7fe3f000)] 0x0904c000 JavaThread "CompilerThread0" daemon [_thread_blocked, id=5077, stack(0x7fe3f000,0x7fec0000)] 0x0904a800 JavaThread "Signal Dispatcher" daemon [_thread_blocked, id=5076, stack(0x7fec0000,0x7ff11000)] 0x09036c00 JavaThread "Finalizer" daemon [_thread_blocked, id=5075, stack(0x7ff57000,0x7ffa8000)] 0x09035400 JavaThread "Reference Handler" daemon [_thread_blocked, id=5074, stack(0x7ffa8000,0x7fff9000)] Other Threads: 0x09031400 VMThread [stack: 0x7fff9000,0x8007a000] [id=5073] 0x09052800 WatcherThread [stack: 0x7fcec000,0x7fd6d000] [id=5080] VM state:not at safepoint (normal execution) VM Mutex/Monitor currently owned by a thread: None Heap PSYoungGen total 46784K, used 32032K [0xae650000, 0xb3440000, 0xb3a50000) eden space 46720K, 68% used [0xae650000,0xb0588f48,0xb13f0000) from space 64K, 95% used [0xb3390000,0xb339f428,0xb33a0000) to space 384K, 0% used [0xb33e0000,0xb33e0000,0xb3440000) PSOldGen total 43008K, used 20872K [0x84650000, 0x87050000, 0xae650000) object space 43008K, 48% used [0x84650000,0x85ab2308,0x87050000) PSPermGen total 16384K, used 5115K [0x80650000, 0x81650000, 0x84650000) object space 16384K, 31% used [0x80650000,0x80b4ec30,0x81650000) Dynamic libraries: 08048000-08052000 r-xp 00000000 08:05 34708 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/bin/java 08052000-08053000 rwxp 00009000 08:05 34708 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/bin/java 08faf000-09220000 rwxp 00000000 00:00 0 [heap] 7e900000-7e9f9000 rwxp 00000000 00:00 0 7e9f9000-7ea00000 ---p 00000000 00:00 0 7ea00000-7ea41000 rwxp 00000000 00:00 0 7ea41000-7eb00000 ---p 00000000 00:00 0 7eb00000-7ebfc000 rwxp 00000000 00:00 0 7ebfc000-7ec00000 ---p 00000000 00:00 0 7ec00000-7ecf7000 rwxp 00000000 00:00 0 7ecf7000-7ed00000 ---p 00000000 00:00 0 7ed00000-7ede7000 rwxp 00000000 00:00 0 7ede7000-7ee00000 ---p 00000000 00:00 0 7eeaf000-7eeb2000 ---p 00000000 00:00 0 7eeb2000-7ef00000 rwxp 00000000 00:00 0 7ef00000-7eff9000 rwxp 00000000 00:00 0 7eff9000-7f000000 ---p 00000000 00:00 0 7f100000-7f1f6000 rwxp 00000000 00:00 0 7f1f6000-7f200000 ---p 00000000 00:00 0 7f200000-7f2fc000 rwxp 00000000 00:00 0 7f2fc000-7f300000 ---p 00000000 00:00 0 7f300000-7f4fe000 rwxp 00000000 00:00 0 7f4fe000-7f500000 ---p 00000000 00:00 0 7f500000-7f5fb000 rwxp 00000000 00:00 0 7f5fb000-7f600000 ---p 00000000 00:00 0 7f600000-7f6f9000 rwxp 00000000 00:00 0 7f6f9000-7f700000 ---p 00000000 00:00 0 7f700000-7f800000 rwxp 00000000 00:00 0 7f830000-7f836000 r-xs 00000000 08:05 241611 /var/cache/fontconfig/945677eb7aeaf62f1d50efc3fb3ec7d8-x86.cache-2 7f836000-7f838000 r-xs 00000000 08:05 241612 /var/cache/fontconfig/99e8ed0e538f840c565b6ed5dad60d56-x86.cache-2 7f838000-7f83b000 r-xs 00000000 08:05 241620 /var/cache/fontconfig/e383d7ea5fbe662a33d9b44caf393297-x86.cache-2 7f83b000-7f846000 r-xs 00000000 08:05 241600 /var/cache/fontconfig/0f34bcd4b6ee430af32735b75db7f02b-x86.cache-2 7f863000-7f866000 ---p 00000000 00:00 0 7f866000-7f8b4000 rwxp 00000000 00:00 0 7f8b4000-7f8b7000 ---p 00000000 00:00 0 7f8b7000-7f905000 rwxp 00000000 00:00 0 7f905000-7f909000 r-xp 00000000 08:05 5012 /usr/lib/libXfixes.so.3.1.0 7f909000-7f90a000 r-xp 00003000 08:05 5012 /usr/lib/libXfixes.so.3.1.0 7f90a000-7f90b000 rwxp 00004000 08:05 5012 /usr/lib/libXfixes.so.3.1.0 7f90b000-7f913000 r-xp 00000000 08:05 5032 /usr/lib/libXrender.so.1.3.0 7f913000-7f914000 r-xp 00007000 08:05 5032 /usr/lib/libXrender.so.1.3.0 7f914000-7f915000 rwxp 00008000 08:05 5032 /usr/lib/libXrender.so.1.3.0 7f915000-7f91e000 r-xp 00000000 08:05 5004 /usr/lib/libXcursor.so.1.0.2 7f91e000-7f91f000 r-xp 00008000 08:05 5004 /usr/lib/libXcursor.so.1.0.2 7f91f000-7f920000 rwxp 00009000 08:05 5004 /usr/lib/libXcursor.so.1.0.2 7f92f000-7f931000 r-xs 00000000 08:05 241622 /var/cache/fontconfig/f24b2111ab8703b4e963115a8cf14259-x86.cache-2 7f931000-7f932000 r-xs 00000000 08:05 241606 /var/cache/fontconfig/4c73fe0c47614734b17d736dbde7580a-x86.cache-2 7f932000-7f936000 r-xs 00000000 08:05 241599 /var/cache/fontconfig/062808c12e6e608270f93bb230aed730-x86.cache-2 7f936000-7f93e000 r-xs 00000000 08:05 241617 /var/cache/fontconfig/d52a8644073d54c13679302ca1180695-x86.cache-2 7f93e000-7f941000 ---p 00000000 00:00 0 7f941000-7f98f000 rwxp 00000000 00:00 0 7f98f000-7fa0e000 r-xp 00000000 08:05 34755 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/libfontmanager.so 7fa0e000-7fa19000 rwxp 0007e000 08:05 34755 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/libfontmanager.so 7fa19000-7fa1d000 rwxp 00000000 00:00 0 7fa1d000-7fa21000 r-xp 00000000 08:05 5008 /usr/lib/libXdmcp.so.6.0.0 7fa21000-7fa22000 rwxp 00003000 08:05 5008 /usr/lib/libXdmcp.so.6.0.0 7fa22000-7fa3e000 r-xp 00000000 08:05 6029 /usr/lib/libxcb.so.1.1.0 7fa3e000-7fa3f000 r-xp 0001c000 08:05 6029 /usr/lib/libxcb.so.1.1.0 7fa3f000-7fa40000 rwxp 0001d000 08:05 6029 /usr/lib/libxcb.so.1.1.0 7fa40000-7fa42000 r-xp 00000000 08:05 4997 /usr/lib/libXau.so.6.0.0 7fa42000-7fa43000 r-xp 00001000 08:05 4997 /usr/lib/libXau.so.6.0.0 7fa43000-7fa44000 rwxp 00002000 08:05 4997 /usr/lib/libXau.so.6.0.0 7fa44000-7fb6e000 r-xp 00000000 08:05 4991 /usr/lib/libX11.so.6.2.0 7fb6e000-7fb6f000 ---p 0012a000 08:05 4991 /usr/lib/libX11.so.6.2.0 7fb6f000-7fb70000 r-xp 0012a000 08:05 4991 /usr/lib/libX11.so.6.2.0 7fb70000-7fb72000 rwxp 0012b000 08:05 4991 /usr/lib/libX11.so.6.2.0 7fb72000-7fb73000 rwxp 00000000 00:00 0 7fb73000-7fb81000 r-xp 00000000 08:05 5010 /usr/lib/libXext.so.6.4.0 7fb81000-7fb82000 r-xp 0000d000 08:05 5010 /usr/lib/libXext.so.6.4.0 7fb82000-7fb83000 rwxp 0000e000 08:05 5010 /usr/lib/libXext.so.6.4.0 7fb83000-7fb84000 r-xs 00000000 08:05 241614 /var/cache/fontconfig/c05880de57d1f5e948fdfacc138775d9-x86.cache-2 7fb84000-7fb87000 r-xs 00000000 08:05 241613 /var/cache/fontconfig/a755afe4a08bf5b97852ceb7400b47bc-x86.cache-2 7fb87000-7fb8a000 r-xs 00000000 08:05 241608 /var/cache/fontconfig/6d41288fd70b0be22e8c3a91e032eec0-x86.cache-2 7fb8a000-7fb92000 r-xs 00000000 08:05 219560 /var/cache/fontconfig/e13b20fdb08344e0e664864cc2ede53d-x86.cache-2 7fb92000-7fbd5000 r-xp 00000000 08:05 34752 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/xawt/libmawt.so 7fbd5000-7fbd7000 rwxp 00043000 08:05 34752 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/xawt/libmawt.so 7fbd7000-7fbd8000 rwxp 00000000 00:00 0 7fbd8000-7fc5c000 r-xp 00000000 08:05 34750 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/libawt.so 7fc5c000-7fc63000 rwxp 00084000 08:05 34750 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/libawt.so 7fc63000-7fc87000 rwxp 00000000 00:00 0 7fc87000-7fc8a000 ---p 00000000 00:00 0 7fc8a000-7fcd8000 rwxp 00000000 00:00 0 7fcd8000-7fceb000 r-xp 00000000 08:05 34739 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/libnet.so 7fceb000-7fcec000 rwxp 00013000 08:05 34739 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/libnet.so 7fcec000-7fced000 ---p 00000000 00:00 0 7fced000-7fd6d000 rwxp 00000000 00:00 0 7fd6d000-7fd70000 ---p 00000000 00:00 0 7fd70000-7fdbe000 rwxp 00000000 00:00 0 7fdbe000-7fdc1000 ---p 00000000 00:00 0 7fdc1000-7fe3f000 rwxp 00000000 00:00 0 7fe3f000-7fe42000 ---p 00000000 00:00 0 7fe42000-7fec0000 rwxp 00000000 00:00 0 7fec0000-7fec3000 ---p 00000000 00:00 0 7fec3000-7ff11000 rwxp 00000000 00:00 0 7ff11000-7ff18000 r-xs 00000000 08:05 134616 /usr/lib/gconv/gconv-modules.cache 7ff18000-7ff57000 r-xp 00000000 08:05 136279 /usr/lib/locale/en_GB.utf8/LC_CTYPE 7ff57000-7ff5a000 ---p 00000000 00:00 0 7ff5a000-7ffa8000 rwxp 00000000 00:00 0 7ffa8000-7ffab000 ---p 00000000 00:00 0 7ffab000-7fff9000 rwxp 00000000 00:00 0 7fff9000-7fffa000 ---p 00000000 00:00 0 7fffa000-800ad000 rwxp 00000000 00:00 0 800ad000-80243000 r-xs 02fb3000 08:05 34883 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/rt.jar 80243000-80244000 ---p 00000000 00:00 0 80244000-802c4000 rwxp 00000000 00:00 0 802c4000-802c5000 ---p 00000000 00:00 0 802c5000-8034d000 rwxp 00000000 00:00 0 8034d000-80365000 rwxp 00000000 00:00 0 80365000-8037a000 rwxp 00000000 00:00 0 8037a000-804b5000 rwxp 00000000 00:00 0 804b5000-804bd000 rwxp 00000000 00:00 0 804bd000-804d5000 rwxp 00000000 00:00 0 804d5000-804ea000 rwxp 00000000 00:00 0 804ea000-80625000 rwxp 00000000 00:00 0 80625000-8064c000 rwxp 00000000 00:00 0 8064c000-8064f000 rwxp 00000000 00:00 0 8064f000-81650000 rwxp 00000000 00:00 0 81650000-84650000 rwxp 00000000 00:00 0 84650000-87050000 rwxp 00000000 00:00 0 87050000-ae650000 rwxp 00000000 00:00 0 ae650000-b3440000 rwxp 00000000 00:00 0 b3440000-b3a50000 rwxp 00000000 00:00 0 b3a50000-b3a52000 r-xs 00000000 08:05 241602 /var/cache/fontconfig/2c5ba8142dffc8bf0377700342b8ca1a-x86.cache-2 b3a52000-b3a5b000 r-xp 00000000 08:05 5018 /usr/lib/libXi.so.6.0.0 b3a5b000-b3a5c000 r-xp 00008000 08:05 5018 /usr/lib/libXi.so.6.0.0 b3a5c000-b3a5d000 rwxp 00009000 08:05 5018 /usr/lib/libXi.so.6.0.0 b3a5d000-b3a66000 rwxp 00000000 00:00 0 b3a66000-b3b1d000 rwxp 00000000 00:00 0 b3b1d000-b3d5d000 rwxp 00000000 00:00 0 b3d5d000-b6b1d000 rwxp 00000000 00:00 0 b6b1d000-b6b2c000 r-xp 00000000 08:05 34735 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/libzip.so b6b2c000-b6b2e000 rwxp 0000e000 08:05 34735 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/libzip.so b6b2e000-b6b38000 r-xp 00000000 08:05 1042 /lib/tls/i686/cmov/libnss_files-2.10.1.so b6b38000-b6b39000 r-xp 00009000 08:05 1042 /lib/tls/i686/cmov/libnss_files-2.10.1.so b6b39000-b6b3a000 rwxp 0000a000 08:05 1042 /lib/tls/i686/cmov/libnss_files-2.10.1.so b6b3a000-b6b43000 r-xp 00000000 08:05 1055 /lib/tls/i686/cmov/libnss_nis-2.10.1.so b6b43000-b6b44000 r-xp 00008000 08:05 1055 /lib/tls/i686/cmov/libnss_nis-2.10.1.so b6b44000-b6b45000 rwxp 00009000 08:05 1055 /lib/tls/i686/cmov/libnss_nis-2.10.1.so b6b45000-b6b4b000 r-xp 00000000 08:05 1028 /lib/tls/i686/cmov/libnss_compat-2.10.1.so b6b4b000-b6b4c000 r-xp 00005000 08:05 1028 /lib/tls/i686/cmov/libnss_compat-2.10.1.so b6b4c000-b6b4d000 rwxp 00006000 08:05 1028 /lib/tls/i686/cmov/libnss_compat-2.10.1.so b6b4d000-b6b54000 r-xs 00035000 08:05 304369 /home/thomas/workspace/sir13/javaclient/jars/javaclient.jar b6b54000-b6b5c000 rwxs 00000000 08:05 393570 /tmp/hsperfdata_thomas/5065 b6b5c000-b6b6f000 r-xp 00000000 08:05 1020 /lib/tls/i686/cmov/libnsl-2.10.1.so b6b6f000-b6b70000 r-xp 00012000 08:05 1020 /lib/tls/i686/cmov/libnsl-2.10.1.so b6b70000-b6b71000 rwxp 00013000 08:05 1020 /lib/tls/i686/cmov/libnsl-2.10.1.so b6b71000-b6b73000 rwxp 00000000 00:00 0 b6b73000-b6b77000 r-xp 00000000 08:05 5038 /usr/lib/libXtst.so.6.1.0 b6b77000-b6b78000 r-xp 00004000 08:05 5038 /usr/lib/libXtst.so.6.1.0 b6b78000-b6b79000 rwxp 00005000 08:05 5038 /usr/lib/libXtst.so.6.1.0 b6b79000-b6b7f000 r-xp 00000000 08:05 34723 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/native_threads/libhpi.so b6b7f000-b6b80000 rwxp 00006000 08:05 34723 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/native_threads/libhpi.so b6b80000-b6b81000 rwxp 00000000 00:00 0 b6b81000-b6b82000 r-xp 00000000 00:00 0 b6b82000-b6ba5000 r-xp 00000000 08:05 34733 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/libjava.so b6ba5000-b6ba7000 rwxp 00023000 08:05 34733 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/libjava.so b6ba7000-b6bae000 r-xp 00000000 08:05 1733 /lib/tls/i686/cmov/librt-2.10.1.so b6bae000-b6baf000 r-xp 00006000 08:05 1733 /lib/tls/i686/cmov/librt-2.10.1.so b6baf000-b6bb0000 rwxp 00007000 08:05 1733 /lib/tls/i686/cmov/librt-2.10.1.so b6bb0000-b6bb3000 ---p 00000000 00:00 0 b6bb3000-b6c01000 rwxp 00000000 00:00 0 b6c01000-b6c25000 r-xp 00000000 08:05 1016 /lib/tls/i686/cmov/libm-2.10.1.so b6c25000-b6c26000 r-xp 00023000 08:05 1016 /lib/tls/i686/cmov/libm-2.10.1.so b6c26000-b6c27000 rwxp 00024000 08:05 1016 /lib/tls/i686/cmov/libm-2.10.1.so b6c27000-b72f4000 r-xp 00000000 08:05 34724 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/server/libjvm.so b72f4000-b7341000 rwxp 006cc000 08:05 34724 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/server/libjvm.so b7341000-b7765000 rwxp 00000000 00:00 0 b7765000-b78a3000 r-xp 00000000 08:05 967 /lib/tls/i686/cmov/libc-2.10.1.so b78a3000-b78a4000 ---p 0013e000 08:05 967 /lib/tls/i686/cmov/libc-2.10.1.so b78a4000-b78a6000 r-xp 0013e000 08:05 967 /lib/tls/i686/cmov/libc-2.10.1.so b78a6000-b78a7000 rwxp 00140000 08:05 967 /lib/tls/i686/cmov/libc-2.10.1.so b78a7000-b78aa000 rwxp 00000000 00:00 0 b78aa000-b78ac000 r-xp 00000000 08:05 1014 /lib/tls/i686/cmov/libdl-2.10.1.so b78ac000-b78ad000 r-xp 00001000 08:05 1014 /lib/tls/i686/cmov/libdl-2.10.1.so b78ad000-b78ae000 rwxp 00002000 08:05 1014 /lib/tls/i686/cmov/libdl-2.10.1.so b78ae000-b78b5000 r-xp 00000000 08:05 34734 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/jli/libjli.so b78b5000-b78b7000 rwxp 00006000 08:05 34734 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/jli/libjli.so b78b7000-b78b8000 rwxp 00000000 00:00 0 b78b8000-b78cd000 r-xp 00000000 08:05 1081 /lib/tls/i686/cmov/libpthread-2.10.1.so b78cd000-b78ce000 r-xp 00014000 08:05 1081 /lib/tls/i686/cmov/libpthread-2.10.1.so b78ce000-b78cf000 rwxp 00015000 08:05 1081 /lib/tls/i686/cmov/libpthread-2.10.1.so b78cf000-b78d1000 rwxp 00000000 00:00 0 b78d1000-b78d2000 r-xs 00000000 08:05 161622 /var/cache/fontconfig/4794a0821666d79190d59a36cb4f44b5-x86.cache-2 b78d2000-b78d4000 r-xs 00000000 08:05 241610 /var/cache/fontconfig/7ef2298fde41cc6eeb7af42e48b7d293-x86.cache-2 b78d4000-b78df000 r-xp 00000000 08:05 34732 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/libverify.so b78df000-b78e0000 rwxp 0000b000 08:05 34732 /usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/libverify.so b78e0000-b78e2000 rwxp 00000000 00:00 0 b78e2000-b78e3000 r-xp 00000000 00:00 0 [vdso] b78e3000-b78fe000 r-xp 00000000 08:05 64 /lib/ld-2.10.1.so b78fe000-b78ff000 r-xp 0001a000 08:05 64 /lib/ld-2.10.1.so b78ff000-b7900000 rwxp 0001b000 08:05 64 /lib/ld-2.10.1.so bfc33000-bfc48000 rwxp 00000000 00:00 0 [stack] VM Arguments: jvm_args: -Dfile.encoding=UTF-8 java_command: Main Launcher Type: SUN_STANDARD Environment Variables: PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games USERNAME=thomas LD_LIBRARY_PATH=/usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/server:/usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386:/usr/lib/jvm/java-6-sun-1.6.0.15/jre/../lib/i386:/usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386/client:/usr/lib/jvm/java-6-sun-1.6.0.15/jre/lib/i386:/usr/lib/xulrunner-addons:/usr/lib/xulrunner-addons SHELL=/bin/bash DISPLAY=:0.0 Signal Handlers: SIGSEGV: [libjvm.so+0x650690], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004 SIGBUS: [libjvm.so+0x650690], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004 SIGFPE: [libjvm.so+0x52f580], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004 SIGPIPE: [libjvm.so+0x52f580], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004 SIGXFSZ: [libjvm.so+0x52f580], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004 SIGILL: [libjvm.so+0x52f580], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004 SIGUSR1: SIG_DFL, sa_mask[0]=0x00000000, sa_flags=0x00000000 SIGUSR2: [libjvm.so+0x532170], sa_mask[0]=0x00000004, sa_flags=0x10000004 SIGHUP: [libjvm.so+0x531ea0], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004 SIGINT: [libjvm.so+0x531ea0], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004 SIGTERM: [libjvm.so+0x531ea0], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004 SIGQUIT: [libjvm.so+0x531ea0], sa_mask[0]=0x7ffbfeff, sa_flags=0x10000004 --------------- S Y S T E M --------------- OS:squeeze/sid uname:Linux 2.6.31-20-generic #57-Ubuntu SMP Mon Feb 8 09:05:19 UTC 2010 i686 libc:glibc 2.10.1 NPTL 2.10.1 rlimit: STACK 8192k, CORE 0k, NPROC infinity, NOFILE 1024, AS infinity load average:1.07 0.55 0.23 CPU:total 2 (2 cores per cpu, 1 threads per core) family 6 model 15 stepping 13, cmov, cx8, fxsr, mmx, sse, sse2, sse3, ssse3 Memory: 4k page, physical 3095836k(1519972k free), swap 1261060k(1261060k free) vm_info: Java HotSpot(TM) Server VM (14.1-b02) for linux-x86 JRE (1.6.0_15-b03), built on Jul 2 2009 15:49:13 by "java_re" with gcc 3.2.1-7a (J2SE release) time: Mon Mar 22 12:08:40 2010 elapsed time: 21 seconds

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• Nested multithread operations tracing

  - by Sinix

  I've a code alike void ExecuteTraced(Action a, string message) { TraceOpStart(message); a(); TraceOpEnd(message); } The callback (a) could call ExecuteTraced again, and, in some cases, asynchronously (via ThreadPool, BeginInvoke, PLINQ etc, so I've no ability to explicitly mark operation scope). I want to trace all operation nested (even if they perform asynchronously). So, I need the ability to get last traced operation inside logical call context (there may be a lot of concurrent threads, so it's impossible to use lastTraced static field). There're CallContext.LogicalGetData and CallContext.LogicalSetData, but unfortunately, LogicalCallContext propagates changes back to the parent context as EndInvoke() called. Even worse, this may occure at any moment if EndInvoke() was called async. http://stackoverflow.com/questions/883486/endinvoke-changes-current-callcontext-why Also, there is Trace.CorrelationManager, but it based on CallContext and have all the same troubles. There's a workaround: use the CallContext.HostContext property which does not propagates back as async operation ended. Also, it does'nt clone, so the value should be immutable - not a problem. Though, it's used by HttpContext and so, workaround is not usable in Asp.Net apps. The only way I see is to wrap HostContext (if not mine) or entire LogicalCallContext into dynamic and dispatch all calls beside last traced operation. Help, please!

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• Help with force close occurrences in my app

  - by Ken

  This is the last issue with this app. Periodic force close situations. I think something should be on another thread but I'm not sure what. Anyway, I can always count on a freeze on first install. If I wait, eventually (maybe 10 seconds) the app comes around, maybe more. here is an excerpt from logcat--the three lines occur after full layout is displayed and I attempt to touch a [game] 'peg' which should spawn a sprite, but the freeze occurs there. Can anybody tell what the issue might be?: I/System.out( 279): TouchDown (17.0,106.0) I/System.out( 279): checking (17,106 I/System.out( 279): hit for bounds Rect(3, 98 - 32, 130) [FREEZE BEGINS] W/webcore ( 279): Can't get the viewWidth after the first layout W/WindowManager( 60): Key dispatching timed out sending to com.live.brainbuilderfree/com.live.brainbuilderfree.BrainBuilderFree W/WindowManager( 60): Previous dispatch state: null W/WindowManager( 60): Current dispatch state: {{null to Window{43fd87a0 com.live.brainbuilderfree/com.live.brainbuilderfree.BrainBuilderFree paused=false} @ 1295232880017 lw=Window{43fd87a0 com.live.brainbuilderfree/com.live.brainbuilderfree.BrainBuilderFree paused=false} lb=android.os.BinderProxy@440523b8 fin=false gfw=true ed=true tts=0 wf=false fp=false mcf=Window{43fd87a0 com.live.brainbuilderfree/com.live.brainbuilderfree.BrainBuilderFree paused=false}}} I/Process ( 60): Sending signal. PID: 279 SIG: 3 I/dalvikvm( 279): threadid=3: reacting to signal 3 D/dalvikvm( 124): GC_EXPLICIT freed 1754 objects / 106104 bytes in 7365ms I/Process ( 60): Sending signal. PID: 60 SIG: 3 I/dalvikvm( 60): threadid=3: reacting to signal 3 I/dalvikvm( 60): Wrote stack traces to '/data/anr/traces.txt' I/Process ( 60): Sending signal. PID: 263 SIG: 3 I/dalvikvm( 263): threadid=3: reacting to signal 3 I/dalvikvm( 279): Wrote stack traces to '/data/anr/traces.txt' I/Process ( 60): Sending signal. PID: 117 SIG: 3 I/dalvikvm( 117): threadid=3: reacting to signal 3 I/dalvikvm( 117): Wrote stack traces to '/data/anr/traces.txt' I/Process ( 60): Sending signal. PID: 254 SIG: 3 I/Process ( 60): Sending signal. PID: 121 SIG: 3 I/dalvikvm( 121): threadid=3: reacting to signal 3 D/AudioSink( 34): bufferCount (4) is too small and increased to 12 I/System.out( 279): making white sprite I/Process ( 60): Sending signal. PID: 186 SIG: 3 I/Process ( 60): Sending signal. PID: 232 SIG: 3 D/MillennialMediaAdSDK( 279): size: 1 D/MillennialMediaAdSDK( 279): num: 1 D/AdWhirl SDK( 279): Millennial success D/AdWhirl SDK( 279): Will call rotateAd() in 120 seconds I/dalvikvm( 232): threadid=3: reacting to signal 3 I/dalvikvm( 121): Wrote stack traces to '/data/anr/traces.txt' I/Process ( 60): Sending signal. PID: 222 SIG: 3 I/MillennialMediaAdSDK( 279): Millennial ad return success D/MillennialMediaAdSDK( 279): View height: 0 D/MillennialMediaAdSDK( 279): nextUrl: [deleted] I/Process ( 60): Sending signal. PID: 239 SIG: 3 I/Process ( 60): Sending signal. PID: 213 SIG: 3 D/AdWhirl SDK( 279): Added subview D/AdWhirl SDK( 279): Pinging URL: [deleted] I/Process ( 60): Sending signal. PID: 197 SIG: 3 I/dalvikvm( 197): threadid=3: reacting to signal 3 I/Process ( 60): Sending signal. PID: 164 SIG: 3 I/dalvikvm( 164): threadid=3: reacting to signal 3 D/dalvikvm( 279): GC_FOR_MALLOC freed 7735 objects / 639688 bytes in 217ms I/Process ( 60): Sending signal. PID: 124 SIG: 3 I/dalvikvm( 124): threadid=3: reacting to signal 3 I/Process ( 60): Sending signal. PID: 158 SIG: 3 I/dalvikvm( 158): threadid=3: reacting to signal 3 I/Process ( 60): Sending signal. PID: 127 SIG: 3 E/ActivityManager( 60): ANR in com.live.brainbuilderfree (com.live.brainbuilderfree/.BrainBuilderFree) E/ActivityManager( 60): Reason: keyDispatchingTimedOut E/ActivityManager( 60): Load: 3.46 / 1.69 / 0.65 E/ActivityManager( 60): CPU usage from 28095ms to 140ms ago: E/ActivityManager( 60): system_server: 30% = 25% user + 4% kernel / faults: 3119 minor 66 major E/ActivityManager( 60): mediaserver: 11% = 7% user + 4% kernel / faults: 746 minor 17 major E/ActivityManager( 60): com.svox.pico: 1% = 0% user + 1% kernel / faults: 2833 minor 8 major E/ActivityManager( 60): d.process.acore: 1% = 0% user + 0% kernel / faults: 1146 minor 36 major E/ActivityManager( 60): ndroid.launcher: 1% = 0% user + 0% kernel / faults: 852 minor 6 major E/ActivityManager( 60): m.android.phone: 0% = 0% user + 0% kernel / faults: 621 minor 7 major E/ActivityManager( 60): kswapd0: 0% = 0% user + 0% kernel E/ActivityManager( 60): ronsoft.openwnn: 0% = 0% user + 0% kernel / faults: 337 minor 2 major E/ActivityManager( 60): adbd: 0% = 0% user + 0% kernel / faults: 3 minor E/ActivityManager( 60): zygote: 0% = 0% user + 0% kernel / faults: 169 minor E/ActivityManager( 60): events/0: 0% = 0% user + 0% kernel E/ActivityManager( 60): rild: 0% = 0% user + 0% kernel / faults: 103 minor 3 major E/ActivityManager( 60): pdflush: 0% = 0% user + 0% kernel E/ActivityManager( 60): .quicksearchbox: 0% = 0% user + 0% kernel / faults: 61 minor E/ActivityManager( 60): id.defcontainer: 0% = 0% user + 0% kernel / faults: 12 minor E/ActivityManager( 60): +rainbuilderfree: 0% = 0% user + 0% kernel E/ActivityManager( 60): +sh: 0% = 0% user + 0% kernel E/ActivityManager( 60): +app_process: 0% = 0% user + 0% kernel E/ActivityManager( 60): TOTAL: 100% = 76% user + 21% kernel + 2% iowait + 0% irq + 0% softirq I/dalvikvm( 127): threadid=3: reacting to signal 3 I/dalvikvm( 186): threadid=3: reacting to signal 3 D/dalvikvm( 60): GC_FOR_MALLOC freed 3747 objects / 228920 bytes in 609ms I/dalvikvm-heap( 60): Grow heap (frag case) to 4.759MB for 36896-byte allocation I/dalvikvm( 239): threadid=3: reacting to signal 3 D/dalvikvm( 60): GC_FOR_MALLOC freed 226 objects / 9952 bytes in 546ms I/dalvikvm( 213): threadid=3: reacting to signal 3 D/dalvikvm( 60): GC_FOR_MALLOC freed 105 objects / 5816 bytes in 492ms I/dalvikvm-heap( 60): Grow heap (frag case) to 4.815MB for 49188-byte allocation I/dalvikvm( 222): threadid=3: reacting to signal 3 D/dalvikvm( 60): GC_FOR_MALLOC freed 77 objects / 5232 bytes in 546ms I/dalvikvm( 254): threadid=3: reacting to signal 3 D/dalvikvm( 60): GC_FOR_MALLOC freed 105 objects / 55856 bytes in 521ms I/dalvikvm-heap( 60): Grow heap (frag case) to 4.876MB for 98360-byte allocation D/dalvikvm( 60): GC_FOR_MALLOC freed 58 objects / 3632 bytes in 340ms D/dalvikvm( 60): GC_FOR_MALLOC freed 1093 objects / 185256 bytes in 572ms W/WindowManager( 60): Continuing to wait for key to be dispatched I/System.out( 279): TouchMove (117.0,124.0) I/System.out( 279): TouchUP (117.0,124.0) D/dalvikvm( 60): GC_FOR_MALLOC freed 141 objects / 108328 bytes in 564ms I/ARMAssembler( 60): generated scanline__00000077:03515104_00000000_00000000 [ 33 ipp] (47 ins) at [0x313d78:0x313e34] in 11621593 ns W/InputManagerService( 60): Window already focused, ignoring focus gain of: com.android.internal.view.IInputMethodClient$Stub$Proxy@43f66a10 I/dalvikvm( 239): Wrote stack traces to '/data/anr/traces.txt' I/dalvikvm( 263): Wrote stack traces to '/data/anr/traces.txt' etc...

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• Is DataRow thread safe? How to update a single datarow in a datatable using multiple threads? - .net

  - by NLV

  Hello all I want to update a single datarow in a datatable using multiple threads. Is this actually possible? I've written the following code implementing a simple multi-threading to update a single datarow. I get different results each time. Why is it so? public partial class Form1 : Form { private static DataTable dtMain; private static string threadMsg = string.Empty; public Form1() { InitializeComponent(); } private void Form1_Load(object sender, EventArgs e) { Thread[] thArr = new Thread[5]; dtMain = new DataTable(); dtMain.Columns.Add("SNo"); DataRow dRow; dRow = dtMain.NewRow(); dRow["SNo"] = 5; dtMain.Rows.Add(dRow); dtMain.AcceptChanges(); ThreadStart ts = new ThreadStart(delegate { dtUpdate(); }); thArr[0] = new Thread(ts); thArr[1] = new Thread(ts); thArr[2] = new Thread(ts); thArr[3] = new Thread(ts); thArr[4] = new Thread(ts); thArr[0].Start(); thArr[1].Start(); thArr[2].Start(); thArr[3].Start(); thArr[4].Start(); while (!WaitTillAllThreadsStopped(thArr)) { Thread.Sleep(500); } foreach (Thread thread in thArr) { if (thread != null && thread.IsAlive) { thread.Abort(); } } dgvMain.DataSource = dtMain; } private void dtUpdate() { for (int i = 0; i < 1000; i++) { try { dtMain.Rows[0][0] = Convert.ToInt32(dtMain.Rows[0][0]) + 1; dtMain.AcceptChanges(); } catch { continue; } } } private bool WaitTillAllThreadsStopped(Thread[] threads) { foreach (Thread thread in threads) { if (thread != null && thread.ThreadState == ThreadState.Running) { return false; } } return true; } } Any thoughts on this? Thank you NLV

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• .NET Process.Kill() in a safe way

  - by Orborde

  I'm controlling a creaky old FORTRAN simulator from a VB.NET GUI, using redirected I/O to communicate with the simulator executable. The GUI pops up a "status" window with a progress bar, estimated time, and a "STOP" button (Button_Stop). Now, I want the Button_Stop to terminate the simulator process immediately. The obvious way to do this is to call Kill() on the Child Process object. This gives an exception if it's done after the process has exited, but I can test whether the process is exited before trying to kill it, right? OK, so I do the following when the button is clicked: If Not Child.HasExited Then Child.Kill() Button_Stop.Enabled = False End If However, what if the process happens to exit between the test and the call to Kill()? In that case, I get an exception. The next thing to occur to me was that I can do Button_Stop.Enabled = False in the Process.Exited event handler, and thus prevent the Child.Kill() call in the Button_Stop.Clicked handler. But since the Process.Exited handler is called on a different thread, that still leaves the following possible interleaving: Child process exits. Process.Exited fires, calls Invoke to schedule the Button_Stop.Enabled = False User clicks on Button_Stop, triggering Child.Kill() Button_Stop.Enabled = False actually happens. An exception would then be thrown on step 3. How do I kill the process without any race conditions? Am I thinking about this entirely wrong?

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• QT- QImage and multi-threading problem.

  - by umanga

  Greetings all, Please refer to image at : http://i48.tinypic.com/316qb78.jpg We are developing an application to extract cell edges from MRC images from electron microscope. MRC file format stores volumetric pixel data (http://en.wikipedia.org/wiki/Voxel) and we simply use 3D char array(char***) to load and store data (gray scale values) from a MRC file. As shown in the image,there are 3 viewers to display XY,YZ and ZX planes respectively. Scrollbars on the top of the viewers use to change the image slice along an axis. Here is the steps we do when user changes the scrollbar position. 1) get the new scrollbar value.(this is the selected slice) 2) for the relavant plane (YZ,XY or ZX), generate (char* slice;) array for the selected slice by reading 3D char array (char***) 3) Create a new QImage* (Format_RGB888) and set pixel values by reading 'slice' (using img-setPixel(x,y,c);) 4) This new QImage* is painted in the paintEvent() method. We are going to execute "edge-detection" process in a seperate thread since it is an intensive process.During this process we need to draw detected curve (set of pixels) on top of above QImage*.(as a layer).This means we need to call drawPoint() methods outside the QT thread. Is it the best wayto use QImage for this case? What is the best way to execute QT drawing methods from another thread? thanks in advance,

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• form update too expensive to be executed in Winform.Timer.Tick

  - by Abruzzo Forte e Gentile

  Hi all I have a WinForm drawing a chart from available data. I programmed it so that every 1 secong the Winform.Timer.Tick event calls a function that: will dequeue all data available will add new points on the chart Right now data to be plotted is really huge and it takes a lot of time to be executed so to update my form. Also Winform.Timer.Tick relies on WM_TIMER , so it executes in the same thread of the Form. Theses 2 things are making my form very UNresponsive. What can I do to solve this issue? I thought the following: moving away from usage of Winform.Timer and start using a System.Threading.Timer use the IsInvokeRequired pattern so I will rely on the .NET ThreadPool. Since I have lots of data, is this a good idea? I have fear that at some point also the ThreadPool will be too long or too big. Can you give me your suggestion about my issue? Thank you very much! AFG

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• Java synchronized seems ignored

  - by viraptor

  Hi, I've got the following code, which I expected to deadlock after printing out "Main: pre-sync". But it looks like synchronized doesn't do what I expect it to. What happens here? import java.util.*; public class deadtest { public static class waiter implements Runnable { Object obj; public waiter(Object obj) { this.obj = obj; } public void run() { System.err.println("Thead: pre-sync"); synchronized(obj) { System.err.println("Thead: pre-wait"); try { obj.wait(); } catch (Exception e) { } System.err.println("Thead: post-wait"); } System.err.println("Thead: post-sync"); } } public static void main(String args[]) { Object obj = new Object(); System.err.println("Main: pre-spawn"); Thread waiterThread = new Thread(new waiter(obj)); waiterThread.start(); try { Thread.sleep(1000); } catch (Exception e) { } System.err.println("Main: pre-sync"); synchronized(obj) { System.err.println("Main: pre-notify"); obj.notify(); System.err.println("Main: post-notify"); } System.err.println("Main: post-sync"); try { waiterThread.join(); } catch (Exception e) { } } } Since both threads synchronize on the created object, I expected the threads to actually block each other. Currently, the code happily notifies the other thread, joins and exits.

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• Guaranteed semaphore order?

  - by Steve_

  The documentation for the .NET Semaphore class states that: There is no guaranteed order, such as FIFO or LIFO, in which blocked threads enter the semaphore. In this case, if I want a guaranteed order (either FIFO or LIFO), what are my options? Is this something that just isn't easily possible? Would I have to write my own Semaphore? I assume that would be pretty advanced? Thanks, Steve

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• Entity Framework lazy loading doesn't work from other thread

  - by Thomas Levesque

  Hi, I just found out that lazy loading in Entity Framework only works from the thread that created the ObjectContext. To illustrate the problem, I did a simple test, with a simple model containing just 2 entities : Person and Address. Here's the code : private static void TestSingleThread() { using (var context = new TestDBContext()) { foreach (var p in context.Person) { Console.WriteLine("{0} lives in {1}.", p.Name, p.Address.City); } } } private static void TestMultiThread() { using (var context = new TestDBContext()) { foreach (var p in context.Person) { Person p2 = p; // to avoid capturing the loop variable ThreadPool.QueueUserWorkItem( arg => { Console.WriteLine("{0} lives in {1}.", p2.Name, p2.Address.City); }); } } } The TestSingleThread method works fine, the Address property is lazily loaded. But in TestMultiThread, I get a NullReferenceException on p2.Address.City, because p2.Address is null. It that a bug ? Is this the way it's supposed to work ? If so, is there any documentation mentioning it ? I couldn't find anything on the subject on MSDN or Google... And more importantly, is there a workaround ? (other than explicitly calling LoadProperty from the worker thread...) Any help would be very appreciated PS: I'm using VS2010, so it's EF 4.0. I don't know if it was the same in the previous version of EF...

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• C# can I lock a method parameter?

  - by 5YrsLaterDBA

  We have a class variable ArrayList binaryScanData in a class. In all methods having access to it, we put lock(binaryScanData) on it because it is shared. Now we want to move one of those methods out to another util class to make it a static method. We will pass that binaryScanData into the method like this: public static void convertAndSaveRawData(ref MemoryStream output, ref ArrayList binaryScanData) Our questions are followed: how can we sychoronize that binaryScanData? can we do the same as it is originally? ref is necessary? It will only be read in that convertAndSaveRawData method.

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• Why isn't the reference counter in boost::shared_ptr volatile?

  - by Johann Gerell

  In the boost::shared_ptr destructor, this is done: if(--*pn == 0) { boost::checked_delete(px); delete pn; } where pn is a pointer to the reference counter, which is typedefed as shared_ptr::count_type -> detail::atomic_count -> long I would have expected the long to be volatile long, given threaded usage and the non-atomic 0-check-and-deletion in the shared_ptr destructor above. Why isn't it volatile?

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• Boost::Thread or fork() : Multithreaded HTTP Proxy

  - by osmano807

  I'm testing boost::thread on a system. It happens that I needed to act as a fork(), because one thread modifies the other variables, even member variables of class I do the project using fork() or is there some alternative still using boost::thread? Basically I run this program in Linux and maybe FreeBSD. It is an http proxy,accept() in main thread, and a function that accepts a class (where there is the file descriptor socket) in a secondary thread that makes the service. Is there a better way to implement a proxy?

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• How do I run different threads in Java?

  - by Cris Carter

  Hey. I'm having some problems with threads. I understand how they work, but since they all use the same method, how do I run different threads that do completely different things, but at the same time? To me, it seems that they always use the same standard method which makes them do the same thing. So, let's say I have a big .txt file where I want to go through each line and do something to the line. In this case, I would like to have each thread do 1/10th of the .txt file, but I don't understand how the threads can communicate with each other, and how they could organize so each thread does the right part? Could anyone explain or help me with this? Would be very much appreciated!

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• How to stop worker threads in a multithreaded Windows service on service stop

  - by RobW

  I have a Windows service that uses the producer/consumer queue model with multiple worker threads processing tasks off a queue. These tasks can be very long running, in the order of many minutes if not hours, and do not involve loops. My question is about the best way to handle the service stop to gracefully end processing on these worker threads. I have read in another SO question that using thread.Abort() is a sign of bad design, but it seems that the service OnStop() method is only given a limited amount of time to finish before the service is terminated. I can do sufficient clean-up in the catch for ThreadAbortException (there is no danger of inconsistent state) so calling thread.Abort() on the worker threads seems OK to me. Is it? What are the alternatives?

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• LWUIT Deadlock (lwuit dialog VS System dialog)

  - by Ramps

  Hi, I have a deadlock problem when I try to make some I/O operations that needs user permission. When user click the button I start a new thread which is responsible for performing IO operations, and I display lwuit "please wait" dialog. Dialog is dismissed by IO thread from callback method. Problem is that, when system dialog appears (asking for user permission ) on top of lwuit dialog - deadlock occurs. I assume that this is because dialog.show() method blocks main thread (EDT), so it's impossible to dismiss system dialog, when lwuit dialog is behind it. Anyone managed to solve this problem? Here is the simplified code, hope it is clear enough: protected void actionPerformed(ActionEvent evt, int id) { switch (id) { case ID_FRIEND: MyRunnableWithIoOperation r = new MyRunnableWithIoOperation(this); new Thread(r).start(); //run the thread performing IO operations Command cmd = mWaitDialog.showDialog(); // show the "please wait" dialog ...//handle cancel }//end switch } /* method called from MyRunnableWithIoOperation, when operation finished*/ public void myCallbackMethod(){ mWaitDialog.dispose(); // } I tried to start my IO thread by calling Display.getInstance().invokeAndBlock( r ), but with no luck. In such case, my "wait dialog" doesn't show up.

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• Delegate within a delegate in VB.NET.

  - by Topdown

  I am trying to write a VB.NET alternative to a C# anonymous function. I wish to call Threading.SynchronizationContext.Current.Send which expects a delegate of type Threading.SendOrPostCallback to be passed to it. The background is here, but because I wish to both pass in a string to MessageBox.Show and also capture the DialogResult I need to define another delegate within. I am struggling with the VB.NET syntax, both from the traditional delegate style, and lambda functions. My go at the traditional syntax is below, but I have gut feeling it should be much simpler than this: Private Sub CollectMesssageBoxResultFromUserAsDelegate(ByVal messageToShow As String, ByRef wasCanceled As Boolean) wasCanceled = False If Windows.Forms.MessageBox.Show(String.Format("{0}{1}Please press [OK] to ignore this error and continue, or [Cancel] to stop here.", messageToShow), "Continue", Windows.Forms.MessageBoxButtons.OKCancel, Windows.Forms.MessageBoxIcon.Exclamation) = Windows.Forms.DialogResult.Cancel Then wasCanceled = True End If End Sub Private Delegate Sub ShowMessageBox(ByVal messageToShow As String, ByRef canceled As Boolean) Private Sub AskUserWhetherToCancel(ByVal message As String, ByVal args As CancelEventArgs) If args Is Nothing Then args = New System.ComponentModel.CancelEventArgs With {.Cancel = False} Dim wasCancelClicked As Boolean Dim firstDelegate As New ShowMessageBox(AddressOf CollectMesssageBoxResultFromUserAsDelegate) '…. Now what?? 'I can’t declare SendOrPostCallback as below: 'Dim myDelegate As New Threading.SendOrPostCallback(AddressOf firstDelegate) End Sub

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• Winforms application hungs when switching to another app

  - by joseluisrod

  Hi, I believe I have a potential threading issue. I have a user control that contains the following code: private void btnVerify_Click(object sender, EventArgs e) { if (!backgroundWorkerVerify.IsBusy) { backgroundWorkerVerify.RunWorkerAsync(); } } private void backgroundWorkerVerify_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e) { VerifyAppointments(); } private void backgroundWorkerVerify_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e) { MessageBox.Show("Information was Verified.", "Verify", MessageBoxButtons.OK, MessageBoxIcon.Information); CloseEvent(); } vanilla code. but the issue I have is that when the application is running and the users tabs to another application when they return to mine the application is hung, they get a blank screen and they have to kill it. This started when I put the threading code. Could I have some rogue threads out there? what is the best way to zero in a threading problem? The issue can't be recreated on my machine...I know I must be missing something on how to dispose of a backgroundworker properly. Any thoughts are appreciated, Thanks, Jose

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• Lock-free multi-threading is for real threading experts...

  - by vdhant

  I was reading through an answer that Jon Skeet gave to a question and in it he mentioned this: As far as I'm concerned, lock-free multi-threading is for real threading experts, of which I'm not one. Its not the first time that I have heard this, but I find very few people talking about how you actually do it if you are interested in learning how to write lock-free multi-threading code. So my question is besides learning all you can about threading, etc where do you start trying to learn to specifically write lock-free multi-threading code and what are some good resources. Cheers

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• Techniques for modeling a dynamic dataflow with Java concurrency API

  - by Maian

  Is there an elegant way to model a dynamic dataflow in Java? By dataflow, I mean there are various types of tasks, and these tasks can be "connected" arbitrarily, such that when a task finishes, successor tasks are executed in parallel using the finished tasks output as input, or when multiple tasks finish, their output is aggregated in a successor task (see flow-based programming). By dynamic, I mean that the type and number of successors tasks when a task finishes depends on the output of that finished task, so for example, task A may spawn task B if it has a certain output, but may spawn task C if has a different output. Another way of putting it is that each task (or set of tasks) is responsible for determining what the next tasks are. Sample dataflow for rendering a webpage: I have as task types: file downloader, HTML/CSS renderer, HTML parser/DOM builder, image renderer, JavaScript parser, JavaScript interpreter. File downloader task for HTML file HTML parser/DOM builder task File downloader task for each embedded file/link If image, image renderer If external JavaScript, JavaScript parser JavaScript interpreter Otherwise, just store in some var/field in HTML parser task JavaScript parser for each embedded script JavaScript interpreter Wait for above tasks to finish, then HTML/CSS renderer (obviously not optimal or perfectly correct, but this is simple) I'm not saying the solution needs to be some comprehensive framework (in fact, the closer to the JDK API, the better), and I absolutely don't want something as heavyweight is say Spring Web Flow or some declarative markup or other DSL. To be more specific, I'm trying to think of a good way to model this in Java with Callables, Executors, ExecutorCompletionServices, and perhaps various synchronizer classes (like Semaphore or CountDownLatch). There are a couple use cases and requirements: Don't make any assumptions on what executor(s) the tasks will run on. In fact, to simplify, just assume there's only one executor. It can be a fixed thread pool executor, so a naive implementation can result in deadlocks (e.g. imagine a task that submits another task and then blocks until that subtask is finished, and now imagine several of these tasks using up all the threads). To simplify, assume that the data is not streamed between tasks (task output-succeeding task input) - the finishing task and succeeding task won't exist together, so the input data to the succeeding task will not be changed by the preceeding task (since it's already done). There are only a couple operations that the dataflow "engine" should be able to handle: A mechanism where a task can queue more tasks A mechanism whereby a successor task is not queued until all the required input tasks are finished A mechanism whereby the main thread (or other threads not managed by the executor) blocks until the flow is finished A mechanism whereby the main thread (or other threads not managed by the executor) blocks until certain tasks have finished Since the dataflow is dynamic (depends on input/state of the task), the activation of these mechanisms should occur within the task code, e.g. the code in a Callable is itself responsible for queueing more Callables. The dataflow "internals" should not be exposed to the tasks (Callables) themselves - only the operations listed above should be available to the task. Note that the type of the data is not necessarily the same for all tasks, e.g. a file download task may accept a File as input but will output a String. If a task throws an uncaught exception (indicating some fatal error requiring all dataflow processing to stop), it must propagate up to the thread that initiated the dataflow as quickly as possible and cancel all tasks (or something fancier like a fatal error handler). Tasks should be launched as soon as possible. This along with the previous requirement should preclude simple Future polling + Thread.sleep(). As a bonus, I would like to dataflow engine itself to perform some action (like logging) every time task is finished or when no has finished in X time since last task has finished. Something like: ExecutorCompletionService<T> ecs; while (hasTasks()) { Future<T> future = ecs.poll(1 minute); some_action_like_logging(); if (future != null) { future.get() ... } ... } Are there straightforward ways to do all this with Java concurrency API? Or if it's going to complex no matter what with what's available in the JDK, is there a lightweight library that satisfies the requirements? I already have a partial solution that fits my particular use case (it cheats in a way, since I'm using two executors, and just so you know, it's not related at all to the web browser example I gave above), but I'd like to see a more general purpose and elegant solution.

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• Java Threading Concept Understanding

  - by Nirmal

  Hello All... Recently I have gone through with one simple threading program, which leads me some issues for the related concepts... My sample program code looks like : class NewThread implements Runnable { Thread t; NewThread() { t = new Thread(this, "Demo Thread"); System.out.println("Child thread: " + t); t.start(); // Start the thread } public void run() { try { for (int i = 5; i > 0; i--) { System.out.println("Child Thread: " + i); Thread.sleep(500); } } catch (InterruptedException e) { System.out.println("Child interrupted."); } System.out.println("Exiting child thread."); } } class ThreadDemo { public static void main(String args[]) { new NewThread(); // create a new thread try { for (int i = 5; i > 0; i--) { System.out.println("Main Thread: " + i); Thread.sleep(1000); } } catch (InterruptedException e) { System.out.println("Main thread interrupted."); } System.out.println("Main thread exiting."); } } Now this program giving me the output as follows : Child thread: Thread[Demo Thread,5,main] Main Thread: 5 Child Thread: 5 Child Thread: 4 Main Thread: 4 Child Thread: 3 Child Thread: 2 Main Thread: 3 Child Thread: 1 Exiting child thread. Main Thread: 2 Main Thread: 1 Main thread exiting. So, that's very much clear to me. But as soon as I am replacing the object creation code (calling of a NewThread class constructor) to as follows : NewThread nt = new NewThread(); // create a new thread the output becomes a bit varied like as follows : Child thread: Thread[Demo Thread,5,main] Main Thread: 5 Child Thread: 5 Child Thread: 4 Child Thread: 3 Main Thread: 4 Child Thread: 2 Child Thread: 1 Main Thread: 3 Exiting child thread. Main Thread: 2 Main Thread: 1 Main thread exiting. And some times it's giving me same output in both the cases. So, i am not getting the exact change in both the scenario. I would like to know that you the variation in the output is coming here ? Thanks in advance...

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• Syncronization Exception

  - by Kurru

  Hi I have two threads, one thread processes a queue and the other thread adds stuff into the queue. I want to put the queue processing thread to sleep when its finished processing the queue I want to have the 2nd thread tell it to wake up when it has added an item to the queue However these functions call System.Threading.SynchronizationLockException: Object synchronization method was called from an unsynchronized block of code on the Monitor.PulseAll(waiting); call, because I havent syncronized the function with the waiting object. [which I dont want to do, i want to be able to process while adding items to the queue]. How can I achieve this? Queue<object> items = new Queue<object>(); object waiting = new object(); 1st Thread public void ProcessQueue() { while (true) { if (items.Count == 0) Monitor.Wait(waiting); object real = null; lock(items) { object item = items.Dequeue(); real = item; } if(real == null) continue; .. bla bla bla } } 2nd Thread involves public void AddItem(object o) { ... bla bla bla lock(items) { items.Enqueue(o); } Monitor.PulseAll(waiting); }

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