Concepts/Synchronization/Race Condition

Race Condition

The same read–compute–write bug class in three domains. Bank balance loses a withdrawal. Lazy initialization leaks an allocation. Ticket booking double-books a seat. Same shape, different surface.

Bank Balance Lazy Initialization Ticket Booking

Steps

1/12

Stateshared + per-thread

T1 local

statusidle

balance—

new_balance—

amount—

shared

shared memoryread

balance100

counter per stepnow = 100

T2 local

statusidle

balance—

new_balance—

amount—

Race conditions are a bug class. Correctness, not latency, is the measurement.

OBSERVED

shared.balance = 100. Both worker threads are idle, waiting for a withdraw call.

Bank Balance

1account = {"balance": 100}
2
3def withdraw(amount):
4    balance = account["balance"]       # read
5    new_balance = balance - amount     # compute
6    account["balance"] = new_balance   # write

Historystep 1 / 12

space · ← → · rstep 1/12

Same race shape, different surface. Walk the other two for the full pattern.

to Lazy Initialization to Ticket Booking