Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> writes: > local_lock_nested_bh() is used within networking where applicable. > Document why it is used and how it behaves. > > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> > --- > Documentation/locking/locktypes.rst | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/Documentation/locking/locktypes.rst b/Documentation/locking/locktypes.rst > index 80c914f6eae7a..4851ec1232058 100644 > --- a/Documentation/locking/locktypes.rst > +++ b/Documentation/locking/locktypes.rst > @@ -204,6 +204,27 @@ per-CPU data structures on a non PREEMPT_RT kernel. > local_lock is not suitable to protect against preemption or interrupts on a > PREEMPT_RT kernel due to the PREEMPT_RT specific spinlock_t semantics. > > +CPU local scope and bottom-half > +------------------------------- > + > +Per-CPU variables that are accessed only in softirq context should not rely on > +the assumption that this context is implicitly protected due to being > +non-preemptible. In a PREEMPT_RT kernel, softirq context is preemptible, and > +synchronizing every bottom-half-disabled section via implicit context results > +in an implicit per-CPU "big kernel lock." > + > +A local_lock_t together with local_lock_nested_bh() and > +local_unlock_nested_bh() for locking operations help to identify the locking > +scope. > + > +With lockdep is enabled, these functions verify that data structure access Did you mean *When* lockdep is enabled? Otherwise no complaints here. jon
