Q.What is race around condition? How is it eliminated?

The race around condition is the repeated, uncontrolled toggling of a clocked (level-triggered) JK flip-flop with J = K = 1 when the clock pulse stays HIGH longer than the flip-flop's propagation delay, leaving the final output uncertain. …

[!TLDR]

Race around is the multiple toggling of a level-triggered JK flip-flop at J = K = 1 when the clock is HIGH longer than the propagation delay; it is removed by master-slave or edge-triggered flip-flops.

In a clocked JK flip-flop built with simple level (pulse) triggering, the toggle condition J = K = 1 causes a problem. While the clock is HIGH, the flip-flop is transparent, and the outputs Q and $\overline{Q}$ are fed back to the input gates. If the clock pulse width is larger than the propagation delay of the flip-flop, the output complements, that complement feeds back, and the output complements again, and so on — the output oscillates (toggles several times) during the single clock pulse. When the clock finally goes LOW the final state of Q is uncertain and cannot be predicted. This unwanted repeated toggling is the race around condition.

It is eliminated by ensuring the flip-flop can change state at most once per clock pulse:

• Master-slave JK flip-flop: two flip-flops in cascade, clocked in anti-phase, so the master accepts the input on one clock edge/level and the slave transfers it on the other — the output changes only once per clock. …