The patch titled
Document the fact that RCU callbacks can run in parallel
has been removed from the -mm tree. Its filename was
document-the-fact-that-rcu-callbacks-can-run-in-parallel.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: Document the fact that RCU callbacks can run in parallel
From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Add an item to the RCU documentation checklist noting that RCU callbacks
can run in parallel.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/RCU/checklist.txt | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff -puN Documentation/RCU/checklist.txt~document-the-fact-that-rcu-callbacks-can-run-in-parallel Documentation/RCU/checklist.txt
--- a/Documentation/RCU/checklist.txt~document-the-fact-that-rcu-callbacks-can-run-in-parallel
+++ a/Documentation/RCU/checklist.txt
@@ -222,7 +222,15 @@ over a rather long period of time, but i
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()),
_
Patches currently in -mm which might be from paulmck@xxxxxxxxxxxxxxxxxx are
origin.patch
immunize-rcu_dereference-against-crazy-compiler-writers.patch
remove-workaround-for-unimmunized-rcu_dereference-from-mce_log.patch
-
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