Had this happen once not fun , though mine was the opposite my master cylinder decided to seize meaning the brakes locked on .
I backed off all adjusters roadside to the end of there adjustment which meant I had one more application before I was really stuffed.
I managed to travel about 250 kms out of a national park and up a highway through some mountains and all the way home without having to touch the pedal.Guess it was unsafe a little bit
but I did have brakes there just if I used them once that was it .