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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2007-07-15 23:41:03 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-16 09:05:47 -0700
commitef48bd246124ccdef0e1fa5b03b62d69cbf71fa7 (patch)
tree830af437b3d0bc916a4f8f9928dece6b64200a66 /Documentation/RCU/checklist.txt
parent4d3b573ad9af85b6df104044f6fff05f04349db2 (diff)
downloadlinux-linaro-stable-ef48bd246124ccdef0e1fa5b03b62d69cbf71fa7.tar.gz
Document the fact that RCU callbacks can run in parallel
Add an item to the RCU documentation checklist noting that RCU callbacks can run in parallel. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/RCU/checklist.txt')
-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()),