35 lines
745 B
Plaintext
35 lines
745 B
Plaintext
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C MP+polockmbonce+poacquiresilsil
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(*
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* Result: Never
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*
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* Do spinlocks combined with smp_mb__after_spinlock() provide order
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* to outside observers using spin_is_locked() to sense the lock-held
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* state, ordered by acquire? Note that when the first spin_is_locked()
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* returns false and the second true, we know that the smp_load_acquire()
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* executed before the lock was acquired (loosely speaking).
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*)
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{}
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P0(spinlock_t *lo, int *x) // Producer
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{
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spin_lock(lo);
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smp_mb__after_spinlock();
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WRITE_ONCE(*x, 1);
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spin_unlock(lo);
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}
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P1(spinlock_t *lo, int *x) // Consumer
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{
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int r1;
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int r2;
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int r3;
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r1 = smp_load_acquire(x);
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r2 = spin_is_locked(lo);
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r3 = spin_is_locked(lo);
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}
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exists (1:r1=1 /\ 1:r2=0 /\ 1:r3=1) (* Bad outcome. *)
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