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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-02-28 16:11:28 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-04-29 08:38:33 -0700 |
| commit | b4c5bf353452c49edd860a67845627c9a8f32638 (patch) | |
| tree | 2831f1d9bf2c3523081312b4d0a5d45eaf19c6a8 /Documentation/RCU/checklist.txt | |
| parent | 96224daa16d6589aff87339cf0f630ef13600a59 (diff) | |
| download | lwn-b4c5bf353452c49edd860a67845627c9a8f32638.tar.gz lwn-b4c5bf353452c49edd860a67845627c9a8f32638.zip | |
documentation: Record rcu_dereference() value mishandling
Recent LKML discussings (see http://lwn.net/Articles/586838/ and
http://lwn.net/Articles/588300/ for the LWN writeups) brought out
some ways of misusing the return value from rcu_dereference() that
are not necessarily completely intuitive. This commit therefore
documents what can and cannot safely be done with these values.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'Documentation/RCU/checklist.txt')
| -rw-r--r-- | Documentation/RCU/checklist.txt | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt index 9d10d1db16a5..877947130ebe 100644 --- a/Documentation/RCU/checklist.txt +++ b/Documentation/RCU/checklist.txt @@ -114,12 +114,16 @@ over a rather long period of time, but improvements are always welcome! http://www.openvms.compaq.com/wizard/wiz_2637.html The rcu_dereference() primitive is also an excellent - documentation aid, letting the person reading the code - know exactly which pointers are protected by RCU. + documentation aid, letting the person reading the + code know exactly which pointers are protected by RCU. Please note that compilers can also reorder code, and they are becoming increasingly aggressive about doing - just that. The rcu_dereference() primitive therefore - also prevents destructive compiler optimizations. + just that. The rcu_dereference() primitive therefore also + prevents destructive compiler optimizations. However, + with a bit of devious creativity, it is possible to + mishandle the return value from rcu_dereference(). + Please see rcu_dereference.txt in this directory for + more information. The rcu_dereference() primitive is used by the various "_rcu()" list-traversal primitives, such |