As a counter-message to lots of the replies here: it is completely fine and normal for a 6 month old to be sleeping for longer stretches or not, depending on the baby. My DD (now 7 months, EBF until 6 months) has been doing 11.30pm-7.30am since 4 months. She has last day feed at 6, bed at 6.30, then the 10.30 feed when we go to bed - so two stretches, one 4 hour one 8 hour. (Between 3 and 4 months she had an extra 2am feed.) Not saying this to brag, just that you are not cruel or neglectful for wanting a similar routine.
Introducing solids threw her off for a couple of weeks, she started waking up every two hours. To start with I assumed it was hunger so was feeding her constantly, which then meant she wasn't feeding so well during the day, and it all started to fall apart. But I figured out that she isn't hungry at all, it's actually wind, which she finds really painful. Feeding helps to shift it around but is only a temporary fix and makes it worse later in night. Now when she wakes up screaming I spend ten minutes bouncing her instead (highly recommend a big yoga ball if you don't have one, SO much better on the knees) and a massive burp will emerge and she'll settle. And I made sure to burp her properly after her final feed and keep her sitting up for a bit afterwards. Gradually as she got more used to solids she stopped waking up and went back to normal.
As an aside, we do controlled crying (though I prefer to call it "wait and see") for daytime naps, which works really well. DD is one of those babies who needs a bit of a shout to relieve tension before settling. I rarely have to wait more than five minutes. But it doesn't work for us during the night wakings, as the problem is wind which she can't get rid of by herself. As always, the annoying golden rule is that all babies are different!