diff options
| author | Jiunn Chang | 2019-06-27 16:01:47 -0500 |
|---|---|---|
| committer | Jonathan Corbet | 2019-06-28 09:10:40 -0600 |
| commit | acb6258acc4fbb76449eec6d0c7ca25254671e31 (patch) | |
| tree | 4495e4d1aafd5a21ff877ece56e779a5866de47c /Documentation/RCU | |
| parent | 62ee81b5681daa781f5e800346ae8654b3e5a864 (diff) | |
doc: RCU callback locks need only _bh, not necessarily _irq
The UP.rst file calls for locks acquired within RCU callback functions
to use _irq variants (spin_lock_irqsave() or similar), which does work,
but can be overkill. This commit therefore instead calls for _bh variants
(spin_lock_bh() or similar), while noting that _irq does work.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Jiunn Chang <c0d1n61at3@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/RCU')
| -rw-r--r-- | Documentation/RCU/UP.rst | 13 |
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, |