9
(1)
這不排列組合嗎
T1 T2 T3 ——16
T1 T3 T2 —— 8
T2 T1 T3 —— 4
T2 T3 T1 —— 4
T3 T1 T2 —— 2
T3 T2 T1 —— 2
(2)
T1 | T2 | T3 |
---|---|---|
Slock A | ||
Y=R(A)=0 | ||
Unlock A | ||
Xlock A | ||
Slock A | ||
A=Y+2 | 等待 | |
W(A) | 等待 | |
Unlock A | 等待 | |
X=R(A)=2 | ||
Unlock A | ||
Xlock A | ||
Slock A | ||
A=X*2=4 | 等待 | |
W(A) | 等待 | |
Unlock A | 等待 | |
Z=R(A)=4 | ||
Unlock A | ||
Xlock A | ||
A=Z**2=16 | ||
W(A) | ||
Unlock A |
A=16
(3)
T1 | T2 | T3 |
---|---|---|
Slock A | ||
Y=R(A)=0 | ||
Unlock A | ||
Slock A | ||
Y=R(A)=0 | ||
Y=R(A)=0 | ||
Xlock A | ||
等待 | Unlock A | |
A=Y+2=2 | ||
W(A) | ||
Unlock A | ||
Slock A | ||
Y=R(A)=2 | ||
Unlock A | ||
Xlock A | ||
Xlock A | ||
等待 | A=Y**2=4 | |
等待 | W(A) | |
等待 | Unlock A | |
A=Y*2=0 | ||
W(A) | ||
Unlock A |
A=0
(4)
T1 | T2 | T3 |
---|---|---|
Slock A | ||
Y=R(A)=0 | ||
Xlock A | ||
A=Y+2=2 | Slock A | |
W(A) | 等待 | |
W(A) | 等待 | |
Unlock A | 等待 | |
X=R(A)=2 | ||
Xlock A | ||
Unlock A | 等待 | Slock A |
A=X*2=4 | 等待 | |
W(A) | 等待 | |
Unlock A | 等待 | |
Z=R(A)=4 | ||
Unlock A | ||
Xlock A | ||
等待 | ||
Unlock A | 等待 | |
A=Z**2=16 | ||
W(A) | ||
Unlock A |
(5)
T1 | T2 | T3 |
---|---|---|
Slock A | ||
Y=R(A)=0 | ||
Slock A | ||
X=R(A)=0 | ||
Xlock A | ||
等待 | ||
等待 | Xlock A | |
等待 | 等待 | Slock A |
等待 | 等待 | Z=R(A)=0 |
等待 | 等待 | Xlock A |
等待 | 等待 | 等待 |
10
一個調度Sc在保證衝突的操作的次序不變的情況下,通過交換兩個事務不衝突操作的次序得到另一個調度Sc’,如果Sc’是串行的,稱調度Sc是衝突可串行化的調度。
經交換得調度: r3(B)w3(B)r2(B)w2(B)r2(A)r1(B)r1(A)w1(A)
等價於一個串行調度T3,T2,T1.所以是衝突可串行化的調度
14
(1)
T1 | T2 |
---|---|
Slock A | |
R(A) | |
Xlock B | |
R(B) | |
B=A+B | |
W(B) | |
W(B) | |
Unlock B | |
Unlock A | |
Slock B | |
R(B) | |
Xlock A | |
R(A) | |
A=A+B | |
W(A) | |
Unlock A | |
Unlock B |
(2)
T1 | T2 |
---|---|
Slock A | |
R(A) | |
Slock B | |
R(B) | |
Xlock B | |
等待 | |
等待 | Xlock A |
等待 | 等待 |