From ef48bd246124ccdef0e1fa5b03b62d69cbf71fa7 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Date: Sun, 15 Jul 2007 23:41:03 -0700 Subject: [PATCH] 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> --- Documentation/RCU/checklist.txt | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) 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()), -- GitLab