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35 lines
825 B
35 lines
825 B
C MP+polocks |
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(* |
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* Result: Never |
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* |
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* This litmus test demonstrates how lock acquisitions and releases can |
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* stand in for smp_load_acquire() and smp_store_release(), respectively. |
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* In other words, when holding a given lock (or indeed after releasing a |
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* given lock), a CPU is not only guaranteed to see the accesses that other |
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* CPUs made while previously holding that lock, it is also guaranteed |
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* to see all prior accesses by those other CPUs. |
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*) |
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{} |
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P0(int *buf, int *flag, spinlock_t *mylock) // Producer |
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{ |
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WRITE_ONCE(*buf, 1); |
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spin_lock(mylock); |
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WRITE_ONCE(*flag, 1); |
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spin_unlock(mylock); |
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} |
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P1(int *buf, int *flag, spinlock_t *mylock) // Consumer |
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{ |
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int r0; |
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int r1; |
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spin_lock(mylock); |
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r0 = READ_ONCE(*flag); |
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spin_unlock(mylock); |
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r1 = READ_ONCE(*buf); |
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} |
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exists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *)
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