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>
This commit is contained in:
Paul E. McKenney 2009-03-10 12:55:57 -07:00 committed by Linus Torvalds
parent be50b8342d
commit 0612ea00a0

View File

@ -298,3 +298,15 @@ over a rather long period of time, but improvements are always welcome!
Note that, rcu_assign_pointer() and rcu_dereference() relate to
SRCU just as they do to other forms of RCU.
15. The whole point of call_rcu(), synchronize_rcu(), and friends
is to wait until all pre-existing readers have finished before
carrying out some otherwise-destructive operation. It is
therefore critically important to -first- remove any path
that readers can follow that could be affected by the
destructive operation, and -only- -then- invoke call_rcu(),
synchronize_rcu(), or friends.
Because these primitives only wait for pre-existing readers,
it is the caller's responsibility to guarantee safety to
any subsequent readers.