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Pthread_setaffinity_np Error 22

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takes a minute: Sign up Pthread_setaffinity_np invalid argument up vote 2 down vote favorite I am trying to change the affinity of each thread inside the start routine. Here's the code. In the below code, 't' is the argument passed through the pthread_create function. cpu_set_t mask; pthread_t c; a = *((int *)t); printf(" thread no. is %d \n",a); CPU_ZERO(&mask); a =a/2 sched_setaffinity example + 1; CPU_SET(a,&mask); c=pthread_self(); s=pthread_setaffinity_np(c,sizeof(cpu_set_t), &mask); if (s!=0) handle_error_en(s,"pthread_setaffinity_np"); The thread affinity is not getting changed. Where am I going wrong? c++ c pthreads setthreadaffinitymask share|improve this question edited Jan 20 '12 at 12:49 BЈовић 36.4k23100176 asked Jan 16 '12 at 21:50 akhil28288 10710 You can replace the entire switch statement with CPU_SET((a/2+1), &mask);, by the way. –Daniel Fischer Jan 16 '12 at 21:57 Ohh Thanks... :P –akhil28288 Jan 16 '12 at 21:59 Perhaps better, to be sure it's evaluated only once, a = a/2+1; CPU_SET(a, &mask);. –Daniel Fischer Jan 16 '12 at 22:05 1 You're passing the same int pointer to all the threads, which all dereference it some time later, after the int has changed. –bk1e Jan 17 '12 at 3:00 1 Also, maybe the function that created the threads returns before they read the int, and something else uses the same stack location. –bk1e Jan 17 '12 at 3:03 | show 3 more comments 1 Answer 1 active oldest votes up vote 1 down vote accepted I had misunderstood

int cpusetsize, const cpu_set_t *mask); int pthread_getaffinity_np(pthread_t tid, int cpusetsize, cpu_set_t *mask); Description pthread_setaffinity_np sets the CPU affinity mask of the thread whose ID is

Set Affinity Linux Example

tid to the value specified by mask. The argument cpusetsize is pthread_attr_setaffinity_np the length (in bytes) of the data pointed to by mask. Normally this argument would be specified pthread_attr_setaffinity_np example as sizeof(cpu_set_t). If the thread specified by tid is not currently running on one of the CPUs specified in mask, then that thread is migrated to one of http://stackoverflow.com/questions/8886778/pthread-setaffinity-np-invalid-argument the CPUs specified in mask. After a call to pthread_setaffinity_np, the set of CPUs on which the thread will actually run is the intersection of the set specified in the mask argument and the set of CPUs actually present on the system. pthread_getaffinity_np writes the affinity mask of the thread whose ID is tid into the cpu_set_t http://www.sourceware.org/pthreads-win32/manual/pthread_setaffinity_np.html structure pointed to by mask. The cpusetsize argument specifies the size (in bytes) of mask. Pthreads-w32 currently ignores the cpusetsize parameter for either function because cpu_set_t is a direct typeset to the Windows affinity vector type DWORD_PTR. Return Value On success, pthread_setaffinity_np and pthread_getaffinity_np return 0. On error, an error number is returned. Errors EFAULT A supplied memory address was invalid. EINVAL The affinity bit mask mask contains no processors that are currently physically on the system. EAGAIN The function did not succeed in changing or obtaining the CPU affinity for some undetermined reason. Try again. EPERM The calling process does not have appropriate privileges. ESRCH The thread whose ID is tid could not be found. Application Usage A thread's CPU affinity mask determines the set of CPUs on which it is eligible to run. On a multiprocessor system, setting the CPU affinity mask can be used to obtain performance benefits. For example, by dedicating one CPU to a particular thread (i.e., setting the affinity mask

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pthread_setaffinity_np error

Pthread setaffinity np Error p size t cpusetsize const cpu set t cpuset int pthread getaffinity np pthread t thread size t cpusetsize cpu set t cpuset Compile and link with -pthread Description The pthread setaffinity np function sets the CPU affinity mask of the thread Pthread setaffinity np Vs Sched setaffinity thread to the CPU set pointed to by cpuset If cpu set t the call is successful and the thread is not currently running on one of the CPUs pthread setaffinity example in cpuset then it is migrated to one of those CPUs The pthread getaffinity np function