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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>
35 lines
762 B
Text
35 lines
762 B
Text
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 *x, int *y, spinlock_t *mylock)
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{
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WRITE_ONCE(*x, 1);
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spin_lock(mylock);
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WRITE_ONCE(*y, 1);
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spin_unlock(mylock);
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}
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P1(int *x, int *y, spinlock_t *mylock)
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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(*y);
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spin_unlock(mylock);
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r1 = READ_ONCE(*x);
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}
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exists (1:r0=1 /\ 1:r1=0)
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