创建线程，但不要立即在Linux中运行

Question

I am trying to execute my program in threads, I use pthread_create() , but it runs the threads immediately. I would like to allow the user to change thread priorities before running. How it is possible to resolve?

for(int i = 0; i < threads; i++)
{
   pthread_create(data->threads+i,NULL,SelectionSort,data);
   sleep(1);
   print(data->array);
}

Answer 1

Set the priority as you create the thread.

Replace

int local_errno;

local_errno = pthread_create(..., NULL, ...);
if (local_errno != 0) { ... }

with

int local_errno;

pthread_attr_t attr;
local_errno = pthread_attr_init(&attr);
if (local_errno != 0) { ... }

{
    struct sched_param sp;
    local_errno = pthread_attr_getschedparam(&attr, &sp);
    if (local_errno != 0) { ... }

    sp.sched_priority = ...;

    local_errno = pthread_attr_setschedparam(&attr, &sp);
    if (local_errno != 0) { ... }
}    

/* So our scheduling priority gets used. */
local_errno = pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED);
if (local_errno != 0) { ... }

local_errno = pthread_create(..., &attr, ...);
if (local_errno != 0) { ... }

local_errno = pthread_attr_destroy(&attr);
if (local_errno != 0) { ... }

Answer 2

For pthreads the priority isn't set after thread creation but rather by passing suitable attributes upon thread creation: the thread attributes go where you have specified NULL in your pthread_create() call. If you want to delay thread creation until the user has given you a priority you can create a function object expecting the priority and upon call of that function object you'd kick off the thread. Of course, you'll still need to keep track of the thus created object (possibly using a std::future<...> -like object) to later join that thread.

Note that providing an answer shouldn't be construed as endorsing thread priorities: as far as I can tell, playing with thread priorities are ill-advised.