Does timer need mutex

0
votes

I use timer in my program:
timer = new Qtimer(); connect(timer, SIGNAL(timeout()), this, SLOT(readData())); timer.start(1000);
And there is also other slots which may be triggered by UI interation:
/*SLOT FUNCTION*/ on_pushbutton_triggered(){..../*write data*/...}.

(the code is written in qt, but I think it's a common question)

So I worry about the potential problem: may readData() reads wrong data while on_pushbutton_triggereed() is writting data?

I am not so familiar with how the timer really work behind the screen: is it in the same thread with my program?
Will readData() and on_pushbutton_triggereed() be called, executed, finished serially and have no mutex problem(that is: I have to use lock() and unlock())? Thank you for reading! I really hope for your hints!

1
multithreadingtimermutex

1 Answers

1
votes

Qt is using an event loop to implement concurrent activity in general and QTimer in particular within a single thread. The event providers (QTimer in this case) are producing events and publish them to the event loop. Then they are processed according to their priority and order of publishing. This approach doesn't require any synchronization as there is only one section of code executed at the time, so it's safe to access data.

On Unix-like systems ps -eLf command will show information about all processes (PID column in the output) and their threads (LWP column). NLWP column shows how many threads particular process has.