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Using xchg for mutual exclusion
nShared
variable b is initialized to 0
nEach
Pi has a local variable k
nThe
only Pi that can enter CS is the one who finds b=0
nThis Pi excludes all the other Pj by
setting b to 1
Process Pi:
repeat
k:=1
repeat xchg(k,b)
until k=0;
CS
b:=0;
RS
forever