AbDndoned Mutexes in Visual Studio .NET

Printer Code 128 in Visual Studio .NET AbDndoned Mutexes
AbDndoned Mutexes
Generating USS Code 128 In Visual Studio .NET
Using Barcode maker for .NET Control to generate, create Code-128 image in Visual Studio .NET applications.
Throughout this chapter, we've encountered a few circumstances in which the topic of abandoned mutexes arose, that is, in the return values of the wait APIs We've deferred a detailed discussion until now An abandoned mutex is a mutex kernel object that was not correctly released before its owning thread terminated This can happen for any number of reasons
Read Code 128B In .NET
Using Barcode decoder for Visual Studio .NET Control to read, scan read, scan image in .NET framework applications.
C h a pter 5 : W i n d ows Ke r n e l Syn c h ro n i z a t i o n
Bar Code Maker In Visual Studio .NET
Using Barcode creation for Visual Studio .NET Control to generate, create barcode image in .NET applications.
Perhaps there i s a bug i n somebody's code and they forgot to release the mutex (or didn't release it enough times, in the case of recursive acquires) Or maybe they remembered to use a try / finally block, but for some reason, the finally block didn' t get a chance to execute This could happen if they are using a machine-wide mutex in a program that gets terminated abruptly, for example, with E x i t P ro c e s s or by acquiring and releasing it from a CLR background thread that was destroyed during process exit As we reviewed in 4, Advanced Threads, there are many cases in native and managed code where finally blocks are not run during process shutdown, and, therefore, any finally blocks on the stack that would have released the mutex won' t get a chance to run An abandoned mutex is prob lematic because it indicates a potential problem with the state protected by that mutex: some code never finished running the critical region, and, therefore, may have left partial state updates and corruption in its wake As soon as the mutex is abandoned, no other thread would be able to acquire it without help from the as, because it' s still marked as being owned This is called orphaning and is discussed more in the next chap ter (particularly since most synchronization primitives don' t tolerate orphaning in the same way that mutexes do) The as deals with this prob lem fairly elegantly If a mutex is abandoned with waiting threads, a wait ing thread will be awakened as though the abandoning thread released it However, when this thread wakes up, it will be told that the mutex has been abandoned via the return value If no waiting thread was awakened, the next thread to wait on the mutex is notified Specifically, the Win32 sin gle object wait functions W a i t F o rS i ngleObject and Wai t F o rS i ngleObj ectEx will return WAIT_ABANDON E D and the multiple object APIs Wait ForMu lt i p l e Obj e c ts and Wa it ForMu ltipleObj ect s E x will return WAIT_ABANDON ED_8 + i , where i is the index of the abandoned mutex in the array of HAND L Es In man aged code, Wai tHand le's wait APIs will throw an Aba ndon edMutex Exception In the case of a W a i t H a n d l e Wa itAny or Wa i t A l l , the index of the mutex (from the array argument passed to the API) is captured in the excep tion's Mutex l n d e x property and the Mutex object itself is accessible from the M u t e x property Despite receiving an error code or exception, when an abandoned mutex is discovered, the calling thread will have success fully acquired the mutex This is important-it means the thread must
Bar Code Reader In Visual Studio .NET
Using Barcode decoder for .NET framework Control to read, scan read, scan image in .NET framework applications.
U s i n g t h e Ke r n e l O b j e c t s
Creating Code 128 Code Set C In C#.NET
Using Barcode drawer for .NET framework Control to generate, create ANSI/AIM Code 128 image in .NET framework applications.
release the mutex when it completes the critical region, just as with any successful acquire Be careful when using a wait-all style wait on an array that contains more than one mutex The WAI T_ABANDON E D_8 + i scheme is only capable of communicating the first abandoned mutex encountered in the array And because the CLR' s Ab a n d o n edMutex E x c e p t i o n builds on top of this same basic support, it too can only communicate one such mutex in the Mut e x
Code 128 Code Set C Drawer In .NET
Using Barcode encoder for ASP.NET Control to generate, create USS Code 128 image in ASP.NET applications.
Code-128 Generator In VB.NET
Using Barcode drawer for Visual Studio .NET Control to generate, create Code128 image in .NET framework applications.
Make Bar Code In .NET
Using Barcode printer for VS .NET Control to generate, create bar code image in Visual Studio .NET applications.
Code 128B Encoder In .NET
Using Barcode drawer for .NET framework Control to generate, create Code 128 Code Set A image in .NET framework applications.
Generating EAN13 In Java
Using Barcode creation for Java Control to generate, create EAN-13 Supplement 5 image in Java applications.
Create Barcode In Visual Studio .NET
Using Barcode generation for ASP.NET Control to generate, create bar code image in ASP.NET applications.
Paint Data Matrix In Java
Using Barcode creator for Java Control to generate, create Data Matrix ECC200 image in Java applications.
UPC Symbol Decoder In VS .NET
Using Barcode recognizer for .NET Control to read, scan read, scan image in .NET applications.