《操作系统》的实验代码。
 
 
 
 
 

30 lines
476 B

.var ticket
.var turn
.var count
.main
.top
.acquire
mov $1, %ax
fetchadd %ax, ticket # grab a ticket (keep it in dx)
.tryagain
mov turn, %cx # check if it's your turn
test %cx, %ax
jne .tryagain
# critical section
mov count, %ax # get the value at the address
add $1, %ax # increment it
mov %ax, count # store it back
# release lock
mov $1, %ax
fetchadd %ax, turn
# see if we're still looping
sub $1, %bx
test $0, %bx
jgt .top
halt