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Top Forums Programming pthread question : global variable not updated Post 302609943 by Corona688 on Tuesday 20th of March 2012 03:42:59 PM
Old 03-20-2012
Threads are independent, remember. You can't make any assumptions about timing unless you enforce them yourself.

Your mutex looks correct, and will stop them from accessing it simultaneously. Nothing stops main() from rolling along and printing the global value before your thread changes it, though!

In fact, it's quite likely. Threads often don't start instantly, it might wait until the next context switch to launch them, and the next context switch could easily be the exit() system call.
 

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PTHREAD_KILL_OTHER_THREADS_NP(3)			     Library Functions Manual				  PTHREAD_KILL_OTHER_THREADS_NP(3)

NAME
pthread_kill_other_threads_np - terminate all threads in program except calling thread SYNOPSIS
#include <pthread.h> void pthread_kill_other_threads_np(void); DESCRIPTION
pthread_kill_other_threads_np is a non-portable LinuxThreads extension. It causes all threads in the program to terminate immediately, except the calling thread which proceeds normally. It is intended to be called just before a thread calls one of the exec functions, e.g. execve(2). Termination of the other threads is not performed through pthread_cancel(3) and completely bypasses the cancellation mechanism. Hence, the current settings for cancellation state and cancellation type are ignored, and the cleanup handlers are not executed in the terminated threads. AUTHOR
Xavier Leroy <Xavier.Leroy@inria.fr> SEE ALSO
execve(2), pthread_setcancelstate(3), pthread_setcanceltype(3), pthread_cancel(3). BUGS
According to POSIX 1003.1c, a successful exec* in one of the threads should terminate automatically all other threads in the program. This behavior is not yet implemented in LinuxThreads. Calling pthread_kill_other_threads_np before exec* achieves much of the same behavior, except that if exec* ultimately fails, then all other threads are already killed. LinuxThreads PTHREAD_KILL_OTHER_THREADS_NP(3)
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