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This commit adds comments to the litmus tests summarizing what these tests are intended to demonstrate. [ paulmck: Apply Andrea's and Alan's feedback. ] Suggested-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: akiyks@gmail.com Cc: boqun.feng@gmail.com Cc: dhowells@redhat.com Cc: j.alglave@ucl.ac.uk Cc: linux-arch@vger.kernel.org Cc: luc.maranget@inria.fr Cc: nborisov@suse.com Cc: npiggin@gmail.com Cc: parri.andrea@gmail.com Cc: stern@rowland.harvard.edu Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1519169112-20593-4-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
40 lines
784 B
Plaintext
40 lines
784 B
Plaintext
C ISA2+pooncerelease+poacquirerelease+poacquireonce
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(*
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* Result: Never
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*
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* This litmus test demonstrates that a release-acquire chain suffices
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* to order P0()'s initial write against P2()'s final read. The reason
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* that the release-acquire chain suffices is because in all but one
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* case (P2() to P0()), each process reads from the preceding process's
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* write. In memory-model-speak, there is only one non-reads-from
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* (AKA non-rf) link, so release-acquire is all that is needed.
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*)
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{}
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P0(int *x, int *y)
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{
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WRITE_ONCE(*x, 1);
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smp_store_release(y, 1);
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}
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P1(int *y, int *z)
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{
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int r0;
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r0 = smp_load_acquire(y);
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smp_store_release(z, 1);
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}
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P2(int *x, int *z)
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{
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int r0;
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int r1;
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r0 = smp_load_acquire(z);
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r1 = READ_ONCE(*x);
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}
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exists (1:r0=1 /\ 2:r0=1 /\ 2:r1=0)
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