| Message ID | 20220509233235.995021-2-dmitry.osipenko@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Introduce power-off+restart call chain API | expand |
On Tue, May 10, 2022 at 1:33 AM Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote: > > Add atomic_notifier_call_chain_is_empty() that returns true if given > atomic call chain is empty. It would be good to mention a use case for it. > Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> > Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com> > --- > include/linux/notifier.h | 2 ++ > kernel/notifier.c | 13 +++++++++++++ > 2 files changed, 15 insertions(+) > > diff --git a/include/linux/notifier.h b/include/linux/notifier.h > index 87069b8459af..95e2440037de 100644 > --- a/include/linux/notifier.h > +++ b/include/linux/notifier.h > @@ -173,6 +173,8 @@ extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh > extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, > unsigned long val_up, unsigned long val_down, void *v); > > +extern bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh); > + > #define NOTIFY_DONE 0x0000 /* Don't care */ > #define NOTIFY_OK 0x0001 /* Suits me */ > #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ > diff --git a/kernel/notifier.c b/kernel/notifier.c > index ba005ebf4730..aaf5b56452a6 100644 > --- a/kernel/notifier.c > +++ b/kernel/notifier.c > @@ -204,6 +204,19 @@ int atomic_notifier_call_chain(struct atomic_notifier_head *nh, > EXPORT_SYMBOL_GPL(atomic_notifier_call_chain); > NOKPROBE_SYMBOL(atomic_notifier_call_chain); > > +/** > + * atomicnotifier_call_chain_is_empty - Check whether notifier chain is empty > + * @nh: Pointer to head of the blocking notifier chain > + * > + * Checks whether notifier chain is empty. > + * > + * Returns true is notifier chain is empty, false otherwise. > + */ > +bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh) > +{ > + return !rcu_access_pointer(nh->head); > +} > + > /* > * Blocking notifier chain routines. All access to the chain is > * synchronized by an rwsem. > -- > 2.35.1 >
On 5/10/22 21:14, Rafael J. Wysocki wrote: > On Tue, May 10, 2022 at 1:33 AM Dmitry Osipenko > <dmitry.osipenko@collabora.com> wrote: >> Add atomic_notifier_call_chain_is_empty() that returns true if given >> atomic call chain is empty. > It would be good to mention a use case for it. > I'll update this patch for v9.
diff --git a/include/linux/notifier.h b/include/linux/notifier.h index 87069b8459af..95e2440037de 100644 --- a/include/linux/notifier.h +++ b/include/linux/notifier.h @@ -173,6 +173,8 @@ extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, unsigned long val_up, unsigned long val_down, void *v); +extern bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh); + #define NOTIFY_DONE 0x0000 /* Don't care */ #define NOTIFY_OK 0x0001 /* Suits me */ #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ diff --git a/kernel/notifier.c b/kernel/notifier.c index ba005ebf4730..aaf5b56452a6 100644 --- a/kernel/notifier.c +++ b/kernel/notifier.c @@ -204,6 +204,19 @@ int atomic_notifier_call_chain(struct atomic_notifier_head *nh, EXPORT_SYMBOL_GPL(atomic_notifier_call_chain); NOKPROBE_SYMBOL(atomic_notifier_call_chain); +/** + * atomicnotifier_call_chain_is_empty - Check whether notifier chain is empty + * @nh: Pointer to head of the blocking notifier chain + * + * Checks whether notifier chain is empty. + * + * Returns true is notifier chain is empty, false otherwise. + */ +bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh) +{ + return !rcu_access_pointer(nh->head); +} + /* * Blocking notifier chain routines. All access to the chain is * synchronized by an rwsem.