Synchronization, barrier
barrier
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barrier All work-items in a work-group executing the kernel on a processor must execute this function before any are allowed to continue execution beyond the barrier.

##

void `barrier` cl_mem_fence_flags flags

## Description

All work-items in a work-group executing the kernel on a processor must execute this function before any are allowed to continue execution beyond the barrier. This function must be encountered by all work-items in a work-group executing the kernel.

If `barrier` is inside a conditional statement, then all work-items must enter the conditional if any work-item enters the conditional statement and executes the `barrier`.

If `barrier` is inside a loop, all work-items must execute the `barrier` for each iteration of the loop before any are allowed to continue execution beyond the `barrier`.

The `barrier` function also queues a memory fence (reads and writes) to ensure correct ordering of memory operations to local or global memory.

The `flags` argument specifies the memory address space and can be set to a combination of the following literal values.

`CLK_LOCAL_MEM_FENCE` - The `barrier` function will either flush any variables stored in local memory or queue a memory fence to ensure correct ordering of memory operations to local memory.

`CLK_GLOBAL_MEM_FENCE` - The `barrier` function will queue a memory fence to ensure correct ordering of memory operations to global memory. This can be useful when work-items, for example, write to buffer or image objects and then want to read the updated data.

## Specification

OpenCL Specification

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