logcat does not work

Sometimes you'll find logcat does not show anything at all in your eclipse. Some people in a forum mention about checking out selected emulator in the DDMS, but that does not work for me. One person says that it's like a temporary eclipse out-of-function on logcat so just restart your eclipse then everything will get back to normal, which does not work for me either. Then I found someone saying press F11 which does thing like restarting a new emulator and run the project in debug mode. I tried it, and it worked for me ! Thank you stranger !