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-rw-r--r--Documentation/RCU/checklist.txt10
1 files changed, 9 insertions, 1 deletions
diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt
index f4dffadbcb00..42b01bc2e1b4 100644
--- a/Documentation/RCU/checklist.txt
+++ b/Documentation/RCU/checklist.txt
@@ -222,7 +222,15 @@ over a rather long period of time, but improvements are always welcome!
deadlock as soon as the RCU callback happens to interrupt that
acquisition's critical section.
-13. SRCU (srcu_read_lock(), srcu_read_unlock(), and synchronize_srcu())
+13. RCU callbacks can be and are executed in parallel. In many cases,
+ the callback code simply wrappers around kfree(), so that this
+ is not an issue (or, more accurately, to the extent that it is
+ an issue, the memory-allocator locking handles it). However,
+ if the callbacks do manipulate a shared data structure, they
+ must use whatever locking or other synchronization is required
+ to safely access and/or modify that data structure.
+
+14. SRCU (srcu_read_lock(), srcu_read_unlock(), and synchronize_srcu())
may only be invoked from process context. Unlike other forms of
RCU, it -is- permissible to block in an SRCU read-side critical
section (demarked by srcu_read_lock() and srcu_read_unlock()),