forked from Minki/linux
rcu: documentation 1Q09 update
Update the RCU documentation to call out the need for callers of primitives like call_rcu() and synchronize_rcu() to prevent subsequent RCU readers from hazard. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -298,3 +298,15 @@ over a rather long period of time, but improvements are always welcome!
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Note that, rcu_assign_pointer() and rcu_dereference() relate to
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SRCU just as they do to other forms of RCU.
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15. The whole point of call_rcu(), synchronize_rcu(), and friends
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is to wait until all pre-existing readers have finished before
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carrying out some otherwise-destructive operation. It is
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therefore critically important to -first- remove any path
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that readers can follow that could be affected by the
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destructive operation, and -only- -then- invoke call_rcu(),
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synchronize_rcu(), or friends.
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Because these primitives only wait for pre-existing readers,
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it is the caller's responsibility to guarantee safety to
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any subsequent readers.
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