Free up space on the drive and the database will carry on working with no additional work on your side. Worst case, if you can't, add a second log file on another drive then figure out why the log space is not being reused.
Also, depending on recovery model, the space in the log should be marked reusable on log backup or checkpoint, if that happens then even if the drive is full the DB goes back to normal because there's free space inside the log file for it to use.
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)SQL In The Wild
: Discussions on DB performance with occasional diversions into recoverability
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