I use the same binary in a initramfs that processes an init script. At the time that it passes off the processing to the busybox on my rootfs as /sbin/init it hangs. If I replace the binaries with an "out of tree" compiled version it works fine. If I replace the installed binary with the binary in the output/build/busybox-1.21.1 it works fine also. In trying to track down the problem I noticed that the installed binary is different from the built binary and was modified 3 minutes later in the build process. I am cross compiling on a Ubuntu 64 bit machine for an arm gaming device.
All binaries are stripped later in the build process, which explains the difference between the binary in output/build/busybox... and the one in output/target. However, stripping should not affect runtime behavior. Have you found a solution to this problem? Is this an unmodified busybox version? A workaround is to specify the busybox binary in option BR2_STRIP_EXCLUDE_FILES but it is not a real solution of course.
Many people are using busybox inside an initramfs without problems. Therefore, I am closing this bug. If you still experience this problem, please reopen and provide more details about this problem, ideally with a reproducible configuration. Thanks.