How to use two threads (GUI and backend)

[Chris Angelico]

On Thu, Oct 27, 2016 at 10:33 PM, jmp <jeanmichel at sequans.com> wrote:
> On 10/27/2016 12:22 PM, pozz wrote:
>>
>> Anyway I don't like this approach, because the main (and single) thread
>> should check in_waiting every X milliseconds.
>> If X is too high, I could wait for the answer even if it is already
>> ready in the input buffer.
>> If X is too low, the application consumes a lot of clocks to check
>> in_waiting.
>>
>> I would prefer to have a callback automatically called when the read
>> operation is complete.  And I think the only method is using another
>> (blocking) thread. The blocking function read returns *immediately* when
>> all the bytes are received.  And I think during blocking time, the
>> thread isn't consuming CPU clocks.
>
>
> Threads do consume CPU clocks.
> An operation within a thread will not consume less CPU clocks, however, the
> scheduler will interrupt the thread and give other threads/operations a
> chance to process as well.
> Threads implement paralellism, not performances.

Blocked threads don't consume CPU time. Why would they?

Remember, folks, *EVERY* program has at least one thread. Threads
aren't some weird and magical thing that you have to be scared of.
They're things you use *all the time*, and they are exactly what
you're used to.

ChrisA