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7e7eb5ae4e
Most Linux-kernel uses of locking are straightforward, but there are corner-case uses that rely on less well-known aspects of the lock and unlock primitives. This commit therefore adds a locking.txt and litmus tests in Documentation/litmus-tests/locking to explain these corner-case uses. [ paulmck: Apply Andrea Parri feedback for klitmus7. ] [ paulmck: Apply Akira Yokosawa example-consistency feedback. ] Reviewed-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
41 lines
640 B
Text
41 lines
640 B
Text
C RM-fixed
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(*
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* Result: Never
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*
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* This litmus test demonstrates that the old "roach motel" approach
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* to locking, where code can be freely moved into critical sections,
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* cannot be used in the Linux kernel.
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*)
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{
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int x;
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atomic_t y;
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}
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P0(int *x, atomic_t *y, spinlock_t *lck)
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{
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int r2;
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spin_lock(lck);
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r2 = atomic_inc_return(y);
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WRITE_ONCE(*x, 1);
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spin_unlock(lck);
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}
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P1(int *x, atomic_t *y, spinlock_t *lck)
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{
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int r0;
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int r1;
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int r2;
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r0 = READ_ONCE(*x);
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r1 = READ_ONCE(*x);
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spin_lock(lck);
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r2 = atomic_inc_return(y);
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spin_unlock(lck);
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}
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locations [x;0:r2;1:r0;1:r1;1:r2]
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filter (1:r0=0 /\ 1:r1=1)
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exists (1:r2=1)
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