barrier

How can we implement dispatch_barrier_async 's equivalent behavior using NSOperationQueue or any user-defined data-structure based on NSOperationQueue ? The requirement is, whenever a barrier operation is submitted it should wait until all non-barrier operations submitted earlier finish their execution and blocks other operations submitted after that. Non-barrier operations should be able to perform concurrently. Barrier operations should execute serially. NB: Not using GCD ,as it doesn't provide(or atleast difficult) much access over the operations, like cancelling single operation, etc. Clay

Unlike barrier() (which I think I understand), mem_fence() does not affect all items in the work group. The OpenCL spec says (section 6.11.10), for mem_fence() : Orders loads and stores of a work-item executing a kernel. (so it applies to a single work item). But, at the same time, in section 3.3.1, it says that: Within a work-item memory has load / store consistency. so within a work item the memory is consistent. So what kind of thing is mem_fence() useful for? It doesn't work across items, yet isn't needed within an item... Note that I haven't used atomic operations (section 9.5 etc). Is

hey last few days I am exploring about the constraint layout.the concept of barrier I can understand but when i implement I can't get the correct output. I want to set the barrier in the right direction to reference Id's. But barrier doesn't work.it should set for the views which are nameLabel and passionLabel. please help me. thank you in advance. This is the current output <?xml version="1.0" encoding="utf-8"?> <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas

I'm building a distributed web server in C/MPI and it seems like point-to-point communication completely stops working after the first MPI_BARRIER in my code. Standard C code works after the barrier, so I know that each of the threads makes it through the barrier. Point-to-point communication also works just fine before the barrier. However, when I copy-paste the same code that worked the line before the barrier into the line after the barrier it stops working entirely. The SEND will just wait forever. When I try using an ISEND instead, it makes it through the line, but the message is never

I understand that DSB, DMB, and ISB are barriers for prevent reordering of instructions. I also can find lots of very good explanations for each of them, but it is pretty hard to imagine the case that I have to use them. Also, from the open source codes, I see those barriers from time to time, but it is quite hard to understand why they are used. Just for an example, in Linux kernel 3.7 tcp_rcv_synsent_state_process function, there is a line as follows: if (unlikely(po->origdev)) sll->sll_ifindex = orig_dev->ifindex; else sll->sll_ifindex = dev->ifindex; smp_mb(); if (po->tp_version <= TPACKET

Nothing prints out in the console in command line tool Xcode when I run the following code: import Foundation class A { var someValue = 0 let concurrentQueue = dispatch_queue_create("queue_for_property", DISPATCH_QUEUE_CONCURRENT) func increaseValueBy1000() { dispatch_barrier_async(concurrentQueue) { for _ in 0 ..< 1000 { let v = self.someValue + 1 print(v) self.someValue = v } } } } let instance1 = A() dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INTERACTIVE, 0)) { instance1.increaseValueBy1000() } instance1.increaseValueBy1000() I don't see any print statement in the console. If I

This question is based on: When is it safe to destroy a pthread barrier? and the recent glibc bug report: http://sourceware.org/bugzilla/show_bug.cgi?id=12674 I'm not sure about the semaphores issue reported in glibc, but presumably it's supposed to be valid to destroy a barrier as soon as pthread_barrier_wait returns, as per the above linked question. (Normally, the thread that got PTHREAD_BARRIER_SERIAL_THREAD , or a "special" thread that already considered itself "responsible" for the barrier object, would be the one to destroy it.) The main use case I can think of is when a barrier is used