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  • What is the best way to deserialize generics written with a different version of a signed assembly?

    - by Rick Minerich
    In other cases it has been suggested that you simply add a SerializationBinder which removes the version from the assembly type. However, when using generic collections of a type found in a signed assembly, that type is strictly versioned based on its assembly. Here is what I've found works. internal class WeaklyNamedAssemblyBinder : SerializationBinder { public override Type BindToType(string assemblyName, string typeName) { ResolveEventHandler handler = new ResolveEventHandler(CurrentDomain_AssemblyResolve); AppDomain.CurrentDomain.AssemblyResolve += handler; Type returnedType; try { AssemblyName asmName = new AssemblyName(assemblyName); var assembly = Assembly.Load(asmName); returnedType = assembly.GetType(typeName); } catch { returnedType = null; } finally { AppDomain.CurrentDomain.AssemblyResolve -= handler; } return returnedType; } Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args) { string truncatedAssemblyName = args.Name.Split(',')[0]; Assembly assembly = Assembly.Load(truncatedAssemblyName); return assembly; } } However, causing the binding process to change globally seems rather dangerous to me. Strange things could happen if serialization was happening in multiple threads. Perhaps a better solution is to do some regex manipulation of the typeName? What do you think?

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  • Thread safe lazy contruction of a singleton in C++

    - by pauldoo
    Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before any code is executed (ie, even before static constructors are executed - their values may already be "initialized" in the program image)? If so - perhaps this can be exploited to implement a singleton mutex - which can in turn be used to guard the creation of the real singleton..) Excellent, it seems that I have a couple of good answers now (shame I can't mark 2 or 3 as being the answer). There appears to be two broad solutions: Use static initialisation (as opposed to dynamic initialisation) of a POD static varible, and implementing my own mutex with that using the builtin atomic instructions. This was the type of solution I was hinting at in my question, and I believe I knew already. Use some other library function like pthread_once or boost::call_once. These I certainly didn't know about - and am very grateful for the answers posted.

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  • What does flushing thread local memory to global memory mean?

    - by Jack Griffith
    Hi, I am aware that the purpose of volatile variables in Java is that writes to such variables are immediately visible to other threads. I am also aware that one of the effects of a synchronized block is to flush thread-local memory to global memory. I have never fully understood the references to 'thread-local' memory in this context. I understand that data which only exists on the stack is thread-local, but when talking about objects on the heap my understanding becomes hazy. I was hoping that to get comments on the following points: When executing on a machine with multiple processors, does flushing thread-local memory simply refer to the flushing of the CPU cache into RAM? When executing on a uniprocessor machine, does this mean anything at all? If it is possible for the heap to have the same variable at two different memory locations (each accessed by a different thread), under what circumstances would this arise? What implications does this have to garbage collection? How aggressively do VMs do this kind of thing? Overall, I think am trying to understand whether thread-local means memory that is physically accessible by only one CPU or if there is logical thread-local heap partitioning done by the VM? Any links to presentations or documentation would be immensely helpful. I have spent time researching this, and although I have found lots of nice literature, I haven't been able to satisfy my curiosity regarding the different situations & definitions of thread-local memory. Thanks very much.

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  • multi-threaded proxy checker having problems

    - by Paul
    hello everyone, I am trying to create a proxy checker. This is my first attempt at multithreading and it's not going so well, the threads seem to be waiting for one to complete before initializing the next. Imports System.Net Imports System.IO Imports System.Threading Public Class Form1 Public sFileName As String Public srFileReader As System.IO.StreamReader Public sInputLine As String Public Class WebCall Public proxy As String Public htmlout As String Public Sub New(ByVal proxy As String) Me.proxy = proxy End Sub Public Event ThreadComplete(ByVal htmlout As String) Public Sub send() Dim myWebRequest As HttpWebRequest = CType(WebRequest.Create("http://www.myserver.com/ip.php"), HttpWebRequest) myWebRequest.Proxy = New WebProxy(proxy, False) Try Dim myWebResponse As HttpWebResponse = CType(myWebRequest.GetResponse(), HttpWebResponse) Dim loResponseStream As StreamReader = New StreamReader(myWebResponse.GetResponseStream()) htmlout = loResponseStream.ReadToEnd() Debug.WriteLine("Finished - " & htmlout) RaiseEvent ThreadComplete(htmlout) Catch ex As WebException If (ex.Status = WebExceptionStatus.ConnectFailure) Then End If Debug.WriteLine("Failed - " & proxy) End Try End Sub End Class Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim proxy As String Dim webArray As New ArrayList() Dim n As Integer For n = 0 To 2 proxy = srFileReader.ReadLine() webArray.Add(New WebCall(proxy)) Next Dim w As WebCall For Each w In webArray Threading.ThreadPool.QueueUserWorkItem(New WaitCallback(AddressOf w.send), w) Next w End Sub Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load srFileReader = System.IO.File.OpenText("proxies.txt") End Sub End Class

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  • MYSQL not running on Ubuntu OS - Error 2002.

    - by mgj
    Hi, I am a novice to mysql DB. I am trying to run the MYSQL Server on Ubuntu 10.04. Through Synaptic Package Manager I am have installed the mysql version: mysql-client-5.1 I wonder that how was the database password set for the mysql-client software that I installed through the above way.It would be nice if you could enlighten me on this. When I tried running this database, I encountered the error given below: mohnish@mohnish-laptop:/var/lib$ mysql ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) mohnish@mohnish-laptop:/var/lib$ I referred to a similar question posted by another user. I didn't find a solution through the proposed answers. For instance when I tried the solutions posted for the similar question I got the following: mohnish@mohnish-laptop:/var/lib$ service start mysqld start: unrecognized service mohnish@mohnish-laptop:/var/lib$ ps -u mysql ERROR: User name does not exist. ********* simple selection ********* ********* selection by list ********* -A all processes -C by command name -N negate selection -G by real group ID (supports names) -a all w/ tty except session leaders -U by real user ID (supports names) -d all except session leaders -g by session OR by effective group name -e all processes -p by process ID T all processes on this terminal -s processes in the sessions given a all w/ tty, including other users -t by tty g OBSOLETE -- DO NOT USE -u by effective user ID (supports names) r only running processes U processes for specified users x processes w/o controlling ttys t by tty *********** output format ********** *********** long options *********** -o,o user-defined -f full --Group --User --pid --cols --ppid -j,j job control s signal --group --user --sid --rows --info -O,O preloaded -o v virtual memory --cumulative --format --deselect -l,l long u user-oriented --sort --tty --forest --version -F extra full X registers --heading --no-heading --context ********* misc options ********* -V,V show version L list format codes f ASCII art forest -m,m,-L,-T,H threads S children in sum -y change -l format -M,Z security data c true command name -c scheduling class -w,w wide output n numeric WCHAN,UID -H process hierarchy mohnish@mohnish-laptop:/var/lib$ which mysql /usr/bin/mysql mohnish@mohnish-laptop:/var/lib$ mysql ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) I even tried referring to http://forums.mysql.com/read.php?11,27769,84713#msg-84713 but couldn't find anything useful. Please let me know how I could tackle this error. Thank you very much..

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  • Fixing a multi-threaded pycurl crash.

    - by Rook
    If I run pycurl in a single thread everything works great. If I run pycurl in 2 threads python will access violate. The first thing I did was report the problem to pycurl, but the project died about 3 years ago so I'm not holding my breath. My (hackish) solution is to build a 2nd version of pycurl called "pycurl_thread" which will only be used by the 2nd thread. I downloaded the pycurl module from sourceforge and I made a total of 4 line changes. But python is still crashing. My guess is that even though this is a module with a different name (import pycurl_thread), its still sharing memory with the original module (import pycurl). How should I solve this problem? Changes in pycurl.c: initpycurl(void) to initpycurl_thread(void) and m = Py_InitModule3("pycurl", curl_methods, module_doc); to m = Py_InitModule3("pycurl_thread", curl_methods, module_doc); Changes in setup.py: PACKAGE = "pycurl" PY_PACKAGE = "curl" to PACKAGE = "pycurl_thread" PY_PACKAGE = "curl_thread" Here is the seg fault i'm getting. This is happening within the C function do_curl_perform(). *** longjmp causes uninitialized stack frame ***: python2.7 terminated ======= Backtrace: ========= /lib/libc.so.6(__fortify_fail+0x37)[0x7f209421b537] /lib/libc.so.6(+0xff4c9)[0x7f209421b4c9] /lib/libc.so.6(__longjmp_chk+0x33)[0x7f209421b433] /usr/lib/libcurl.so.4(+0xe3a5)[0x7f20931da3a5] /lib/libpthread.so.0(+0xfb40)[0x7f209532eb40] /lib/libc.so.6(__poll+0x53)[0x7f20941f6203] /usr/lib/libcurl.so.4(Curl_socket_ready+0x116)[0x7f2093208876] /usr/lib/libcurl.so.4(+0x2faec)[0x7f20931fbaec] /usr/local/lib/python2.7/dist-packages/pycurl.so(+0x892b)[0x7f209342c92b] python2.7(PyEval_EvalFrameEx+0x58a1)[0x4adf81] python2.7(PyEval_EvalCodeEx+0x891)[0x4af7c1] python2.7(PyEval_EvalFrameEx+0x538b)[0x4ada6b] python2.7(PyEval_EvalFrameEx+0x65f9)[0x4aecd9]

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  • [iPhone] UIScrollView notifications

    - by ryyst
    Hi, I'm coding an app that works much like Apple's Weather.app: There's a UIPageControl at the bottom and a UIScrollView in the middle of the screen. In my code, I implemented the - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView method to figure out when the user did move to a new page. If they move to a new page, I load the adjacent pages' data, as to make further page-switching faster. (In one of Apple's examples, the - (void)scrollViewDidScroll:(UIScrollView *)sender is used, but that causes my app to shortly hang when loading a new page, so it's not suitable.) That code works very well. I'm using scrollRectToVisible:: to programmatically scroll inside the scrollview when the user clicks the UIPageControl. The problem is that the scrollRectToVisible: doesn't post a notification to the UIScrollViewDelegate when it's done scrolling - so the code responsible for loading adjacent pages never get's called when using the UIPageControl. Is there any way to make the UIScrollView notify its delegate when it gets called by the scrollRectToVisible: method? Or will I have to use threads in order to prevent my app from freezing? Thanks! -- Ry

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  • Devise routes to only use custom sign in page

    - by eblume
    I am trying to learn Devise and seem to have hit a problem that is nearly the same as many, many questions here on SO but just slightly different enough that I am not getting much traction following those questions' threads. I have a very simple application. Users can sign in and sign out (and also the devise 'forgot password' stuff is enabled - I am not concerned about it at this time) and that is it. They can't register, they can't edit their profile other than to change their password, they can't do anything except sign in and sign out. (Account creation will, for now, be handled manually at the command line.) I would vastly prefer that the only page that users can log in from was "/" (root_path). I already have it working where you can log in from "/", and that is great. The problem I am having is that if you type in your user/password combination incorrectly from the root_path login page, it automatically sends you to the Devise sign-in page to continue trying to sign in. How can I make Devise redirect to root_path on sign-in failure? Here are my routes - they are probably not optimal or correctly configured and I would appreciate pointers on fixing them: root to: "core_pages#splash" devise_for :users, skip: [:sessions] as :user do # get 'signin' => 'devise/sessions#new', as: :new_user_session post 'signin' => 'devise/sessions#create', as: :user_session delete 'signout' => 'devise/sessions#destroy', as: :destroy_user_session, via: Devise.mappings[:user].sign_out_via end match '/home' => 'core_pages#home' Note the commented-out 'get signin' line. The system works without this line but, surprisingly (to me), "GET /signin" results in a HTTP 400 (OK) response and renders the Devise login template. I would prefer it return some sort of 'invalid request' or just silently redirect the user to root_path. Running rake routes on these routes gives: root / core_pages#splash user_password POST /users/password(.:format) devise/passwords#create new_user_password GET /users/password/new(.:format) devise/passwords#new edit_user_password GET /users/password/edit(.:format) devise/passwords#edit PUT /users/password(.:format) devise/passwords#update user_session POST /signin(.:format) devise/sessions#create destroy_user_session DELETE /signout(.:format) devise/sessions#destroy home /home(.:format) core_pages#home Thanks!

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  • How do I DYNAMICALLY cast in C# and return for a property

    - by ken-forslund
    I've already read threads on the topic, but can't find a solution that fits. I'm working on a drop-down list that takes an enum and uses that to populate itself. i found a VB.NET one. During the porting process, I discovered that it uses DirectCast() to set the type as it returns the SelectedValue. See the original VB here: http://jeffhandley.com/archive/2008/01/27/enum-list-dropdown-control.aspx the gist is, the control has Type _enumType; //gets set when the datasource is set and is the type of the specific enum The SelectedValue property kind of looks like (remember, it doesn't work): public Enum SelectedValue //Shadows Property { get { // Get the value from the request to allow for disabled viewstate string RequestValue = this.Page.Request.Params[this.UniqueID]; return Enum.Parse(_enumType, RequestValue, true) as _enumType; } set { base.SelectedValue = value.ToString(); } } Now this touches on a core point that I think was missed in the other discussions. In darn near every example, folks argued that DirectCast wasn't needed, because in every example, they statically defined the type. That's not the case here. As the programmer of the control, I don't know the type. Therefore, I can't cast it. Additionally, the following examples of lines won't compile because c# casting doesn't accept a variable. Whereas VB's CType and DirectCast can accept Type T as a function parameter: return Enum.Parse(_enumType, RequestValue, true); or return Enum.Parse(_enumType, RequestValue, true) as _enumType; or return (_enumType)Enum.Parse(_enumType, RequestValue, true) ; or return Convert.ChangeType(Enum.Parse(_enumType, RequestValue, true), _enumType); or return CastTo<_enumType>(Enum.Parse(_enumType, RequestValue, true)); So, any ideas on a solution? What's the .NET 3.5 best way to resolve this?

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  • What is the best way to save the environment from before an alarm handler goes off when the alarm do

    - by EpsilonVector
    I'm trying to implement user threads on a 2.4 Linux kernel (homework) and the trick for context switch seems to be using an alarm that goes off every x milliseconds and sends us to an alarm handler from which we can longjmp to the next thread. What I'm having difficulties with is figuring out how to save the environment to return to later. Basically I have an array of jmp_buffs, and every time a "context switch" using the alarm happens I want to save the previous context to the appropriate entry of the array and longjmp to the next one. However, just the fact that I need to do this from the event handler means that just using setjmp in the event handler won't give me exactly the kind of environment I want (as far as stack and program counter are involved) because the stack has the event handler call in it and the pc is in the event handler. I suppose I can look at the stack and alter it to fit my needs, but that feels a bit cumbersome. Another idea I had is to somehow pass the environment before the jump to event handler as a parameter to the event handler, but I can't figure out if this is possible. So I guess my question is- how do I do this right?

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  • pthread with unique struct as parameter C

    - by sergiobuj
    Hi, i have this piece of code that is giving me trouble. I know all the threads are reading the same struct. But i have no idea how to fix this. #include <pthread.h> #include <stdio.h> #include <stdlib.h> typedef struct { int a,b; } s_param; void * threadfunc(void *parm) { s_param *param2 = parm; printf("ID:%d and v:%d\n",param2->a,param2->b); pthread_exit(NULL); } int main(int argc, char **argv) { pthread_t thread[3]; int rc=0,i; void * status; for(i=0; i<3 ; ++i){ s_param param; param.b=10; param.a=i; rc = pthread_create(&thread[i], NULL, threadfunc, &param ); // !!!! if(rc){ exit(1); } } for(i=0; i<3 ; ++i){ pthread_join(thread[i],&status); } return 0; } output: ID:2 and v:10 ID:2 and v:10 ID:2 and v:10 and what i need: ID:0 and v:10 ID:1 and v:10 ID:2 and v:10 Thank you.

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  • XElement vs Dcitionary

    - by user135498
    Hi All, I need advice. I have application that imports 10,000 rows containing name & address from a text file into XElements that are subsequently added to a synchronized queue. When the import is complete the app spawns worker threads that process the XElements by deenqueuing them, making a database call, inserting the database output into the request document and inserting the processed document into an output queue. When all requests have been processed the output queue is written to disk as an XML doc. I used XElements for the requests because I needed the flexibility to add fields to the request during processing. i.e. Depending on the job type the app might require that it add phone number, date of birth or email address to a request based on a name/address match against a public record database. My questions is; The XElements seems to use quite a bit of memory and I know there is a lot of parsing as the document makes its way through the processing methods. I’m considering replacing the XElements with a Dictionary object but I’m skeptical the gain will be worth the effort. In essence it will accomplish the same thing. Thoughts?

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  • Do you like Twisted?

    - by Luca
    I use Python Twisted for web development, and I don't like it? I know async programming is a great idea, I know there are may async web servers now, I know it's the only way to solve some problems you'd have with threads but I don't like. The problem is that, you're forced to program in a twisted way. So, the architecture you have in mind, very often have to be modified to fit the way twisted works. The architecture have to follow the technology, I don't think this is good. When we use callback in javascript, we don't have too many difficulties: things are usually simpler, we use a callback in response to an Ajax call. But in a server web app things are, very often, a bit more complex. Writing chain of callbacks don't seem to me a wonderful way of programming. The code is not simple, and so it is difficult to understand and to maintain. Writing twisted code we very often lost the linear intuitive idea of the algorithm we wanted to implement, especially when things grow in complexity. What's your point of view?

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  • Java assignment issues - Is this atomic?

    - by Bob
    Hi, I've got some questions about Java's assigment. Strings I've got a class: public class Test { private String s; public synchronized void setS(String str){ s = s + " - " + str; } public String getS(){ return s; } } I'm using "synchronized" in my setter, and avoiding it in my getter, because in my app, there are a tons of data gettings, and very few settings. Settings must be synchronized to avoid inconsistency. My question is: is getting and setting a variable atomic? I mean, in a multithreaded environment, Thread1 is about to set variable s, while Thread2 is about to get "s". Is there any way the getter method could get something different than the s's old value or the s's new value (suppose we've got only two threads)? In my app it is not a problem to get the new value, and it is not a problem to get the old one. But could I get something else? What about HashMap's getting and putting? considering this: public class Test { private Map<Integer, String> map = Collections.synchronizedMap(new HashMap<Integer, String>()); public synchronized void setMapElement(Integer key, String value){ map.put(key, value); } public String getValue(Integer key){ return map.get(key); } } Is putting and getting atomic? How does HashMap handle putting an element into it? Does it first remove the old value and put the now one? Could I get other than the old value or the new value? Thanks in advance!

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  • Understanding Java Wait and Notify methods

    - by Maddy
    Hello all: I have a following program: import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class SimpleWaitNotify implements Runnable { final static Object obj = new Object(); static boolean value = true; public synchronized void flag() { System.out.println("Before Wait"); try { obj.wait(); } catch (InterruptedException e) { System.out.println("Thread interrupted"); } System.out.println("After Being Notified"); } public synchronized void unflag() { System.out.println("Before Notify All"); obj.notifyAll(); System.out.println("After Notify All Method Call"); } public void run() { if (value) { flag(); } else { unflag(); } } public static void main(String[] args) throws InterruptedException { ExecutorService pool = Executors.newFixedThreadPool(4); SimpleWaitNotify sWait = new SimpleWaitNotify(); pool.execute(sWait); SimpleWaitNotify.value = false; SimpleWaitNotify sNotify = new SimpleWaitNotify(); pool.execute(sNotify); pool.shutdown(); } } When I wait on obj, I get the following exception Exception in thread "pool-1-thread-1" java.lang.IllegalMonitorStateException: current thread not owner for each of the two threads. But if I use SimpleWaitNotify's monitor then the program execution is suspended. In other words, I think it suspends current execution thread and in turn the executor. Any help towards understanding what's going on would be duly appreciated. This is an area1 where the theory and javadoc seem straightforward, and since there aren't many examples, conceptually left a big gap in me.

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  • bad_alloc occuring when allocating small structs

    - by SalamiArmi
    A bad_alloc has started showing up in some code which looks perfectly valid to me and has worked very well in the past. The bad alloc only occurs once every 50-3000 iterations of the code, which is also confusing. The code itself is from a singly linked list, simply adding a new element to the queue: template<typename T> struct container { inline container() : next(0) {} container *next; T data; }; void push(const T &data) { container<T> *newQueueMember = new container<T>; //... unrelated to crash } Where T is: struct test { int m[256]; }; Changing the size of the array allocated array to anything but very small values (1-8 ints) still results in a bad_alloc occasionally. A few extra notes about my program: - I used Poco::ThreadPool to thread my program. I've only recently added this functionality, before I had it running with Win32 threads. However, only the main thread ever calls push(). - I am also occasionally getting other crashes which could be related. However, when I try to debug with visual studio 2008, I can't navigate back to the call stack, or the crash happens deep within new(). Thanks in advance.

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  • How to migrate primary key generation from "increment" to "hi-lo"?

    - by Bevan
    I'm working with a moderate sized SQL Server 2008 database (around 120 tables, backups are around 4GB compressed) where all the table primary keys are declared as simple int columns. At present, primary key values are generated by NHibernate with the increment identity generator, which has worked well thus far, but precludes moving to a multiprocessing environment. Load on the system is growing, so I'm evaluating the work required to allow the use of multiple servers accessing a common database backend. Transitioning to the hi-lo generator seems to be the best way forward, but I can't find a lot of detail about how such a migration would work. Will NHibernate automatically create rows in the hi-lo table for me, or do I need to script these manually? If NHibernate does insert rows automatically, does it properly take account of existing key values? If NHibernate does take care of thing automatically, that's great. If not, are there any tools to help? Update NHibernate's increment identifier generator works entirely in-memory. It's seeded by selecting the maximum value of used identifiers from the table, but from that point on allocates new values by a simple increment, without reference back to the underlying database table. If any other process adds rows to the table, you end up with primary key collisions. You can run multiple threads within the one process just fine, but you can't run multiple processes. For comparison, the NHibernate identity generator works by configuring the database tables with identity columns, putting control over primary key generation in the hands of the database. This works well, but compromises the unit of work pattern. The hi-lo algorithm sits inbetween these - generation of primary keys is coordinated through the database, allowing for multiprocessing, but actual allocation can occur entirely in memory, avoiding problems with the unit of work pattern.

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  • Recommendations of a high volume log event viewer in a Java enviroment

    - by Thorbjørn Ravn Andersen
    I am in a situation where I would like to accept a LOT of log events controlled by me - notably the logging agent I am preparing for slf4j - and then analyze them interactively. I am not as such interested in a facility that presents formatted log files, but one that can accept log events as objects and allow me to sort and display on e.g. threads and timelines etc. Chainsaw could maybe be an option but is currently not compatible with logback which I use for technical reasons. Is there any project with stand alone viewers or embedded in an IDE which would be suitable for this kind of log handling. I am aware that I am approaching what might be suitable for a profiler, so if there is a profiler projekt suitable for this kind of data acquisition and display where I can feed the event pipe, I would like to hear about it). Thanks for all feedback Update 2009-03-19: I have found that there is not a log viewer which allows me to see what I would like (a visual display of events with coordinates determined by day and time, etc), so I have decided to create a very terse XML format derived from the log4j XMLLayout adapted to be as readable as possible while still being valid XML-snippets, and then use the Microsoft LogParser to extract the information I need for postprocessing in other tools.

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  • core dump during std::_List_node_base::unhook()

    - by Ron
    I have a program where std::list is used. The program uses threads which act on the std::list as producers and consumers. When a message is dealt with by the consumer, it is removed from the list using pop_front(). But, during pop_front, there is a core dump. The gdb trace is as below. could you help getting me some insights into this issue? (gdb) bt full 0 0xf7531d7b in std::_List_node_base::unhook () from /usr/lib/libstdc++.so.6 No symbol table info available. 1 0x0805c600 in std::list ::_M_erase (this=0x806b08c, __position={_M_node = 0x8075308}) at /opt/target/usr/include/c++/4.2.0/bits/stl_list.h:1169 __n = (class std::_List_node<myMsg> *) 0x0 2 0x0805c6af in std::list ::pop_front (this=0x806b08c) at /opt/target/usr/include/c++/4.2.0/bits/stl_list.h:750 No locals. 3 0x0805afb6 in Base::run () at ../../src/Base.cc:342 nSentBytes = 130 tmpnm = {_vptr.myMsg = 0x80652c0, m_msg = 0x8075140 "{0130,MSG_TYPE=ND_FUNCTION,ORG_PNAME=P01vm01Ax,FUNCTION=LOG,PARAM_CNT=3,DATETIME=06/12/2010 02:59:26.187,LOGNAME=N,ENTRY=Debug 0 }", m_from = 0x8096ee0 "P01vm01Ax", m_to = 0x0, static m_logged = false, static m_pLogMutex = {_data = {_lock = 0, __count = 0, __owner = 0, __kind = 0, _nusers = 0, {_spins = 0, _list = {_next = 0x0}}}, __size = '\0' , __align = 0}} newMsg = {_vptr.myMsg = 0x80652c0, m_msg = 0x0, m_from = 0x0, m_to = 0x0, static m_logged = false, static m_pLogMutex = {_data = {_lock = 0, __count = 0, __owner = 0, __kind = 0, _nusers = 0, {_spins = 0, _list = {_next = 0x0}}}, __size = '\0' , __align = 0}} strBuffer = "{0440,MSG_TYPE=NG_FUNCTION,ORG_PNAME=mach01./opt/abc/VAvsk/abc/comp/DML/gendrs.pl.17560,DST_PNAME=P01vm01Ax,FUNCTION=DRS_REPLICATE,CAUSE_DML_ERROR=N,CORRUPT_DATA=N,CORRUPT_HEADER=N,DEBUG=Y,EXTENDED_RU"... fds = {{fd = 5, events = 1, revents = 0}} retval = 0 iWaitTime = 0 4 0x0805b277 in startRun () at ../../src/Base.cc:454 No locals. 5 0xf7effe7b in start_thread () from /lib/libpthread.so.0 No symbol table info available. 6 0xf744d82e in clone () from /lib/libc.so.6 No symbol table info available.

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  • Atomic int writes on file

    - by Waneck
    Hello! I'm writing an application that will have to be able to handle many concurrent accesses to it, either by threads as by processes. So no mutex'es or locks should be applied to this. To make the use of locks go down to a minimum, I'm designing for the file to be "append-only", so all data is first appended to disk, and then the address pointing to the info it has updated, is changed to refer to the new one. So I will need to implement a small lock system only to change this one int so it refers to the new address. How is the best way to do it? I was thinking about maybe putting a flag before the address, that when it's set, the readers will use a spin lock until it's released. But I'm afraid that it isn't at all atomic, is it? e.g. a reader reads the flag, and it is unset on the same time, a writer writes the flag and changes the value of the int the reader may read an inconsistent value! I'm looking for locking techniques but all I find is either for thread locking techniques, or to lock an entire file, not fields. Is it not possible to do this? How do append-only databases handle this? Thanks! Cauê

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  • FILE* issue PPU side code

    - by Cristina
    We are working on a homework on CELL programming for college and their feedback response to our questions is kinda slow, thought i can get some faster answers here. I have a PPU side code which tries to open a file passed down through char* argv[], however this doesn't work it cannot make the assignment of the pointer, i get a NULL. Now my first idea was that the file isn't in the correct directory and i copied in every possible and logical place, my second idea is that maybe the PPU wants this pointer in its LS area, but i can't deduce if that's the bug or not. So... My question is what am i doing wrong? I am working with a Fedora 7 SDK Cell, with Eclipse as an IDE. Maybe my argument setup is wrong tho he gets the name of the file correctly. Code on request: images_t *read_bin_data(char *name) { FILE *file; images_t *img; uint32_t *buffer; uint8_t buf; unsigned long fileLen; unsigned long i; //Open file file = (FILE*)malloc(sizeof(FILE)); file = fopen(name, "rb"); printf("[Debug]Opening file %s\n",name); if (!file) { fprintf(stderr, "Unable to open file %s", name); return NULL; } //....... } Main launch: int main(int argc,char* argv[]) { int i,img_width; int modif_this[4] __attribute__ ((aligned(16))) = {1,2,3,4}; images_t *faces, *nonfaces; spe_context_ptr_t ctxs[SPU_THREADS]; pthread_t threads[SPU_THREADS]; thread_arg_t arg[SPU_THREADS]; //intializare img_width img_width = atoi(argv[1]); printf("[Debug]Img size is %i\n",img_width); faces = read_bin_data(argv[3]); //....... } Thanks for the help.

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  • How do JVM's implicit memory barriers behave when chaining constructors

    - by Joonas Pulakka
    Referring to my earlier question on incompletely constructed objects, I have a second question. As Jon Skeet pointed out, there's an implicit memory barrier in the end of a constructor that makes sure that final fields are visible to all threads. But what if a constructor calls another constructor; is there such a memory barrier in the end of each of them, or only in one being called from outside? That is, when the "wrong" solution is: public class ThisEscape { public ThisEscape(EventSource source) { source.registerListener( new EventListener() { public void onEvent(Event e) { doSomething(e); } }); } } And the correct one would be a factory method version: public class SafeListener { private final EventListener listener; private SafeListener() { listener = new EventListener() { public void onEvent(Event e) { doSomething(e); } } } public static SafeListener newInstance(EventSource source) { SafeListener safe = new SafeListener(); source.registerListener(safe.listener); return safe; } } Would the following work too, or not? public class MyListener { private final EventListener Listener; private MyListener() { listener = new EventListener() { public void onEvent(Event e) { doSomething(e); } } } public MyListener(EventSource source) { this(); source.register(listener); } }

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  • pthread condition variables on Linux, odd behaviour.

    - by janesconference
    Hi. I'm synchronizing reader and writer processes on Linux. I have 0 or more process (the readers) that need to sleep until they are woken up, read a resource, go back to sleep and so on. Please note I don't know how many reader processes are up at any moment. I have one process (the writer) that writes on a resource, wakes up the readers and does its business until another resource is ready (in detail, I developed a no starve reader-writers solution, but that's not important). To implement the sleep / wake up mechanism I use a Posix condition value, pthread_cond_t. The clients call a pthread_cond_wait() on the variable to sleep, while the server does a pthread_cond_broadcast() to wake them all up. As the manual says, I surround these two calls with a lock/unlock of the associated pthread mutex. The condition variable and the mutex are initialized in the server and shared between processes through a shared memory area (because I'm not working with threads, but with separate processes) an I'm sure my kernel / syscall support it (because I checked _POSIX_THREAD_PROCESS_SHARED). What happens is that the first client process sleeps and wakes up perfectly. When I start the second process, it blocks on its pthread_cond_wait() and never wakes up, even if I'm sure (by the logs) that pthread_cond_broadcast() is called. If I kill the first process, and launch another one, it works perfectly. In other words, the condition variable pthread_cond_broadcast() seems to wake up only one process a time. If more than one process wait on the very same shared condition variable, only the first one manages to wake up correctly, while the others just seem to ignore the broadcast. Why this behaviour? If I send a pthread_cond_broadcast(), every waiting process should wake up, not just one (and, however, not always the same one).

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  • Should a new language compiler target the JVM?

    - by Pindatjuh
    I'm developing a new language. My initial target was to compile to native x86 for the Windows platform, but now I am in doubt. I've seen some new languages target the JVM (most notable Scala and Clojure). Ofcourse it's not possible to port every language easily to the JVM; to do so, it may lead to small changes to the language and it's design. So that's the reason behind this doubt, and thus this question: Is targetting the JVM a good idea, when creating a compiler for a new language? Or should I stick with x86? I have experience in generating JVM bytecode. Are there any workarounds to JVM's GC? The language has deterministic implicit memory management. How to produce JIT-compatible bytecode, such that it will get the highest speedup? Is it similar to compiling for IA-32, such as the 4-1-1 muops pattern on Pentium? I can imagine some advantages (please correct me if I'm wrong): JVM bytecode is easier than x86. Like x86 communicates with Windows, JVM communicates with the Java Foundation Classes. To provide I/O, Threading, GUI, etc. Implementing "lightweight"-threads.I've seen a very clever implementation of this at http://www.malhar.net/sriram/kilim/. Most advantages of the Java Runtime (portability, etc.) The disadvantages, as I imagined, are: Less freedom? On x86 it'll be more easy to create low-level constructs, while JVM has a higher level (more abstract) processor. Most disadvantages of the Java Runtime (no native dynamic typing, etc.)

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  • InvalidOperationException when executing SqlCommand with transaction

    - by Serhat Özgel
    I have this code, running parallel in two separate threads. It works fine for a few times, but at some random point it throws InvalidOperationException: The transaction is either not associated with the current connection or has been completed. At the point of exception, I am looking inside the transaction with visual studio and verify its connection is set normally. Also command.Transaction._internalTransaction. _transactionState is set to Active and IsZombied property is set to false. This is a test application and I am using Thread.Sleep for creating longer transactions and causing overlaps. Why may the exception being thrown and what can I do about it? IDbCommand command = new SqlCommand("Select * From INFO"); IDbConnection connection = new SqlConnection(connectionString); command.Connection = connection; IDbTransaction transaction = null; try { connection.Open(); transaction = connection.BeginTransaction(); command.Transaction = transaction; command.ExecuteNonQuery(); // Sometimes throws exception Thread.Sleep(forawhile); // For overlapping transactions running in parallel transaction.Commit(); } catch (ApplicationException exception) { if (transaction != null) { transaction.Rollback(); } } finally { connection.Close(); }

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