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Commit 586dd56a authored by Paul E. McKenney's avatar Paul E. McKenney
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Documentation/memory-barriers.txt: Conditional must use prior load 



A control dependency consists of a load, a conditional that depends on
that load, and a store.  This commit emphasizes this point in the
summary.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent 449f7413

Documentation/memory-barriers.txt

+2 −1
Original line number Diff line number Diff line
@@ -724,7 +724,8 @@ In summary: 
      later loads, smp_mb().



  (*) Control dependencies require at least one run-time conditional

      between the prior load and the subsequent store.  If the compiler

      between the prior load and the subsequent store, and this

      conditional must involve the prior load.  If the compiler

      is able to optimize the conditional away, it will have also

      optimized away the ordering.  Careful use of ACCESS_ONCE() can

      help to preserve the needed conditional.