# FPlatformProcess::Sleep crash in thread - bad thread use ? (flicker effect on damage)

**URL:** <https://forums.unrealengine.com/t/fplatformprocess-sleep-crash-in-thread-bad-thread-use-flicker-effect-on-damage/93260>\
**Category:** C++\
**Tags:** unreal-engine\
**Created:** [May 29, 2017, 11:15pm UTC](https://forums.unrealengine.com/t/fplatformprocess-sleep-crash-in-thread-bad-thread-use-flicker-effect-on-damage/93260 "2017-05-29T23:15:16Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![anonymous\_user\_b709974b](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_b709974b](https://forums.unrealengine.com/u/anonymous_user_b709974b)\
**Post date:** [May 29, 2017, 11:15pm UTC](https://forums.unrealengine.com/t/fplatformprocess-sleep-crash-in-thread-bad-thread-use-flicker-effect-on-damage/93260/1 "2017-05-29T23:15:16Z")

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Hi,

I call a function called

```auto

twinkleDamage

```

when my enemy is touched.

I tried many different AsyncTask(ENamedThreads::XXX)  
and it seems that more prioritized is the thread, the more the game freeze when the thread is called.

VisualStudio break point when FPlatformProcess::Sleep is called

```auto

void AMyBasicMob::twinkleDamage()
{

		AsyncTask(ENamedThreads::AnyBackgroundHiPriTask , [this]() // GAMETHREAD ???
		{

			int i = 0;
			bool val = false;
			auto _mesh = this->GetMesh();
			if (_mesh) {
				while (i < 14) {
					UE_LOG(LogClass, Warning, TEXT("FLICKER LOOP"));

					if (!val) {
						_mesh->SetMaterial(0, FlikkerMaterial);
					}
					else {
						_mesh->SetMaterial(0, BaseMaterial);
					}

                                       // HERE ISSUE
                                       // trigger breakpoint or crash
					FPlatformProcess::Sleep(0.03);
                                        ////////////////
                                       ///////////
					val = !val;
					i++;
				}
				_mesh->SetMaterial(0, BaseMaterial);
				this->hitable = true;

			}
		});
	
}

```

As you probably guest, I’m a newbie in UE4, but I’ve done many c++ projects by the past,  
So somebody can tell me what’s wrong here?

Or If you have a best practice for thread that handle visual modification of actor, let me know!

thanks 🙂

---

<div class="post-metadata">

**Author:** ![eyosido](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@eyosido](https://forums.unrealengine.com/u/eyosido)\
**Post date:** [June 9, 2017, 1:07pm UTC](https://forums.unrealengine.com/t/fplatformprocess-sleep-crash-in-thread-bad-thread-use-flicker-effect-on-damage/93260/2 "2017-06-09T13:07:21Z")

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It is likely the calls you are making from inside the thread are not meant to be made outside of the game thread. I am not even sure logging is safe from a non-game thread! Safest position I think is not to make any engine call from a non-game thread, only handle logic there then send messages to the game thread so code there can actually call the engine. However if an UE expert could elaborate on this I would also be interested.