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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>
30 lines
494 B
Text
30 lines
494 B
Text
C R+mbonceonces
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(*
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* Result: Never
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*
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* This is the fully ordered (via smp_mb()) version of one of the classic
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* counterintuitive litmus tests that illustrates the effects of store
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* propagation delays. Note that weakening either of the barriers would
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* cause the resulting test to be allowed.
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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_mb();
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WRITE_ONCE(*y, 1);
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}
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P1(int *x, int *y)
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{
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int r0;
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WRITE_ONCE(*y, 2);
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smp_mb();
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r0 = READ_ONCE(*x);
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}
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exists (y=2 /\ 1:r0=0)
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