clWaitForEvents

Waits on the host thread for commands identified by event objects to complete.

cl_int clWaitForEvents ( cl_uint num_events,
  const cl_event *event_list)

Parameters

event_list

The events specified in event_list act as synchronization points.

Notes

Waits on the host thread for commands identified by event objects in event_list to complete. A command is considered complete if its execution status is CL_COMPLETE or a negative value. The events specified in event_list act as synchronization points.

If the cl_khr_gl_event extension is enabled, event objects can also be used to reflect the status of an OpenGL sync object. The sync object in turn refers to a fence command executing in an OpenGL command stream. This provides another method of coordinating sharing of buffers and images between OpenGL and OpenCL.

If the cl_khr_egl_event extension is enabled, Event objects can also be used to reflect the status of an EGL fence sync object. The sync object in turn refers to a fence command executing in an EGL client API command stream. This provides another method of coordinating sharing of EGL / EGL client API objects with OpenCL. Completion of EGL / EGL client API commands may be determined by placing an EGL fence command after commands using eglCreateSyncKHR, creating an event from the resulting EGL sync object using clCreateEventFromEGLsyncKHR and then specifying it in the event_wait_list of a clEnqueueAcquire*** command. This method may be considerably more efficient than calling operations like glFinish, and is referred to as explicit synchronization. The application is responsible for ensuring the command stream associated with the EGL fence is flushed to ensure the CL queue is submitted to the device. Explicit synchronization is most useful when an EGL client API context bound to another thread is accessing the memory objects."

Errors

Returns CL_SUCCESS if the execution status of all events in event_list is CL_COMPLETE. Otherwise, it returns one of the following errors:

  • CL_INVALID_VALUE if num_events is zero or event_list is NULL..
  • CL_INVALID_CONTEXT if events specified in event_list do not belong to the same context.
  • CL_INVALID_EVENT if event objects specified in event_list are not valid event objects.
  • CL_EXEC_STATUS_ERROR_FOR_EVENTS_IN_WAIT_LIST if the execution status of any of the events in event_list is a negative integer value.
  • CL_OUT_OF_RESOURCES if there is a failure to allocate resources required by the OpenCL implementation on the device.
  • CL_OUT_OF_HOST_MEMORY if there is a failure to allocate resources required by the OpenCL implementation on the host.

Specification

OpenCL Specification

Also see

clGetEventInfo, clReleaseEvent, clRetainEvent, cl_khr_gl_event, cl_khr_egl_event

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