Why does a blocked channel in one kernel also block other kernels' running?

Thanks, HRZ.

I just tested this with emulator (with the option "-emulator-channel-depth-model=strict"). My host code is very simple and no kernels are waiting for any events. I show the key code as follows (you can see I put Producer and Consumer into two different command queues, respectively). It is really weird.

#define MAX_CMD_QUEUES 4
#define N_KERNEL 2
 
void run_kernel(cl_command_queue cmd_queue[MAX_CMD_QUEUES], cl_kernel (&kernel)[N_KERNEL], size_t n_thread)
{
    size_t global_work_size[1] = {(size_t)n_thread};
    size_t local_work_size[1] = {(size_t)n_thread};
 
    cl_event event_write[1], event_exec[2];
    cl_int status;
    cl_command_queue &rcmd_queue0 = cmd_queue[0], &rcmd_queue1 = cmd_queue[1], &rcmd_queue2 = cmd_queue[2];
 
    // Write data into buf_in from h_in
    status = clEnqueueWriteBuffer(rcmd_queue0, buf_in, CL_TRUE, 0, bufsize, h_in, 0, NULL, event_write);
    error_check(status, "Write buf_in failed!\n");
 
    // Launch the kernel Producer
    status = clEnqueueNDRangeKernel(rcmd_queue0, kernel[0], 1, NULL, global_work_size, local_work_size, 1, event_write, NULL);
    error_check(status, "Run kernel Producer error!\n");
 
    // Launch the kernel Consumer
    status = clEnqueueNDRangeKernel(rcmd_queue1, kernel[1], 1, NULL, global_work_size, local_work_size, 0, NULL, NULL);
    error_check(status, "Run kernel Consumer error!\n");
 
    // Read results back to h_out from buf_out
    read_back_results(rcmd_queue1, bufsize, buf_out, (char*)h_out, NULL);
 
    clReleaseEvent(event_write[0]);
    clReleaseEvent(event_exec[0]);
    clReleaseEvent(event_exec[1]);
}

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