Timer (System.Threading) thread safety

Question

Does anyone know if this code would be thread safe, or do I have to use lock when calling timer2.Change?

Timer timer1 = new Timer(timerCallback1);
Timer timer2 = new Timer(timerCallback2);
timer1.Change(5000, 5000);
timer2.Change(3000, 3000);

public void timerCallback1(object state)
{
    timer1.Change(Timeout.Infinite, Timeout.Infinite);
    timer2.Change(Timeout.Infinite, Timeout.Infinite);

    DoStuff();

    timer1.Change(5000, 5000);
    timer2.Change(3000, 3000);
}

score 6 · Accepted Answer · answered Jun 16 '10 at 14:23

6

It's "thread-safe" in the sense that the call to Change won't actually corrupt the timer.

However, it's not "thread-safe" in the sense that you definitely have a race condition (it's not possible to ensure that timerCallback2 isn't running when you're in DoStuff).

answered Jun 16 '10 at 14:23

Stephen Cleary

437,863
77
675
810

Thanks, yes maybe I'll do a Sleep before DoStuff() to give timerCallback2 time to finish, or I'll just add a lock. – remdao Jun 17 '10 at 08:35

score 2 · Answer 2 · answered Jun 16 '10 at 14:22

2

Per MSDN documentation the Timer type is thread safe, so the only place you have to be careful is where you call DoStuff();.

answered Jun 16 '10 at 14:22

Tony The Lion

61,704
67
242
415

I read "Any instance members are _not_ thread-safe". http://msdn.microsoft.com/en-us/library/system.timers.timer.aspx – H H Jun 16 '10 at 14:26
1

@Henk: Thats in the System.Timers class, not the Threading.Timer Class, which is thread safe – Tony The Lion Jun 16 '10 at 14:37

Timer (System.Threading) thread safety

2 Answers2

Linked