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documentation: State that rcu_dereference() reloads pointer

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Make a note stating that repeated calls of rcu_dereference() may not
return the same pointer if update happens while in critical section.

Reported-by: Jeff Haran <jeff.haran@citrix.com>
Signed-off-by: Milos Vyletel <milos@redhat.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Milos Vyletel 2015-04-17 16:38:04 +02:00 committed by Paul E. McKenney
parent ee7c29be36
commit ed38446424
1 changed files with 3 additions and 1 deletions
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4
Documentation/RCU/whatisRCU.txt
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@ -256,7 +256,9 @@ rcu_dereference()
If you are going to be fetching multiple fields from the
RCU-protected structure, using the local variable is of
course preferred. Repeated rcu_dereference() calls look
ugly and incur unnecessary overhead on Alpha CPUs.
ugly, do not guarantee that the same pointer will be returned
if an update happened while in the critical section, and incur
unnecessary overhead on Alpha CPUs.
Note that the value returned by rcu_dereference() is valid
only within the enclosing RCU read-side critical section.