There is almost always something you can be doing for a few hours while waiting for reviews. Start looking at the next piece of work you are going to be tackling. Study code you might be working with in the future. Read up on libraries or tools that you are not completely familiar with. Read good general programming books or blogs. However I'll assume you have done all those things, or that the delays have got longer than a few hours, and you;ve run out of things on your TODO list.
As Joe Strazzere says. talk to your boss. Ask two things:
- What should you do when waiting for the reviews
- More importantly, is there a way of getting a faster turnround on your reviews.
Faster turnround on your reviews has several benefits, as well as not blocking you. You will better understand the feedback on your reviews if they turn round fairly quickly. You also have to 'context switch' less if reviews come back to you sooner, improving your productivity. There is also less chance of change conflicts.
It varies between companies, depending largely on how detailed the reviews have to be, but reviews generally shouldn't take more than a day or so, and less is preferable. Ask your boss what turnround is expected, and if there is anything that can be done to reduce it. Also note whether it is a few people who take longer than others to do their reviews.