Two instances of eclipse opening each time

Whenever I am trying to o开发者_运维知识库pen eclipse, two instances of it pointing to the same workspace is opened every time. When I close one, both of them get closed.

Is it some feature I accidentally enabled? How to revert it back ?

Perhaps you have Clicked on Window/New Window? That would open a second eclipse window with the same workspace. Normally a workspace cannot be open in two different eclipse instances.

When you try to close one of the windows using the close-button in the window decoration, you should be able to get back to normal one-window-mode.

It is not possible to open two instances pointing to the same workspace. Are you sure that two instances are actually being opened (and not just two entries in the task bar)? You can probably check the process list to confirm that two instances are indeed being launched.