rcu: add shiny new debug assists to Documentation/RCU/checklist.txt

Add a section describing PROVE_RCU, DEBUG_OBJECTS_RCU_HEAD, and
the __rcu sparse checking to the RCU checklist.

Suggested-by: David Miller <davem@davemloft.net>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt
index 790d1a8123760211bdcb6427b75c1b4abf2b7210..c7c6788956f40a3428f677b69874dded3b7d8a2b 100644 (file)
--- a/Documentation/RCU/checklist.txt
+++ b/Documentation/RCU/checklist.txt
@@ -365,3 +365,26 @@ over a rather long period of time, but improvements are always welcome!
        and the compiler to freely reorder code into and out of RCU
        read-side critical sections.  It is the responsibility of the
        RCU update-side primitives to deal with this.
+
+17.    Use CONFIG_PROVE_RCU, CONFIG_DEBUG_OBJECTS_RCU_HEAD, and
+       the __rcu sparse checks to validate your RCU code.  These
+       can help find problems as follows:
+
+       CONFIG_PROVE_RCU: check that accesses to RCU-protected data
+               structures are carried out under the proper RCU
+               read-side critical section, while holding the right
+               combination of locks, or whatever other conditions
+               are appropriate.
+
+       CONFIG_DEBUG_OBJECTS_RCU_HEAD: check that you don't pass the
+               same object to call_rcu() (or friends) before an RCU
+               grace period has elapsed since the last time that you
+               passed that same object to call_rcu() (or friends).
+
+       __rcu sparse checks: tag the pointer to the RCU-protected data
+               structure with __rcu, and sparse will warn you if you
+               access that pointer without the services of one of the
+               variants of rcu_dereference().
+
+       These debugging aids can help you find problems that are
+       otherwise extremely difficult to spot.