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-rw-r--r--Documentation/RCU/UP.rst13
1 files changed, 7 insertions, 6 deletions
diff --git a/Documentation/RCU/UP.rst b/Documentation/RCU/UP.rst
index 67715a47ae89..e26dda27430c 100644
--- a/Documentation/RCU/UP.rst
+++ b/Documentation/RCU/UP.rst
@@ -113,12 +113,13 @@ Answer to Quick Quiz #1:
Answer to Quick Quiz #2:
What locking restriction must RCU callbacks respect?
- Any lock that is acquired within an RCU callback must be
- acquired elsewhere using an _irq variant of the spinlock
- primitive. For example, if "mylock" is acquired by an
- RCU callback, then a process-context acquisition of this
- lock must use something like spin_lock_irqsave() to
- acquire the lock.
+ Any lock that is acquired within an RCU callback must be acquired
+ elsewhere using an _bh variant of the spinlock primitive.
+ For example, if "mylock" is acquired by an RCU callback, then
+ a process-context acquisition of this lock must use something
+ like spin_lock_bh() to acquire the lock. Please note that
+ it is also OK to use _irq variants of spinlocks, for example,
+ spin_lock_irqsave().
If the process-context code were to simply use spin_lock(),
then, since RCU callbacks can be invoked from softirq context,