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| author | Milos Vyletel <milos@redhat.com> | 2015-04-17 16:38:04 +0200 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-05-27 12:57:28 -0700 |
| commit | ed38446424dd531f1b7a167677232a6d400d69d5 (patch) | |
| tree | 061898389cefd9fd56264e1b4391134cd42e2cac /Documentation/RCU/whatisRCU.txt | |
| parent | ee7c29be3695996536395f647e8a2ed6b1ab3a0d (diff) | |
| download | lwn-ed38446424dd531f1b7a167677232a6d400d69d5.tar.gz lwn-ed38446424dd531f1b7a167677232a6d400d69d5.zip | |
documentation: State that rcu_dereference() reloads pointer
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>
Diffstat (limited to 'Documentation/RCU/whatisRCU.txt')
| -rw-r--r-- | Documentation/RCU/whatisRCU.txt | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt index 88dfce182f66..16622c9e86b5 100644 --- a/Documentation/RCU/whatisRCU.txt +++ b/Documentation/RCU/whatisRCU.txt @@ -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. |