| Message ID | 20211027211715.12671-4-digetx@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested, archived |
| Headers | show |
| Series | Introduce power-off+restart call chain API | expand |
On Thu, Oct 28, 2021 at 12:16:33AM +0300, Dmitry Osipenko wrote: > Add atomic/blocking_notifier_has_unique_priority() helpers which return > true if given handler has unique priority. ... > +/** > + * atomic_notifier_has_unique_priority - Checks whether notifier's priority is unique > + * @nh: Pointer to head of the atomic notifier chain > + * @n: Entry in notifier chain to check > + * > + * Checks whether there is another notifier in the chain with the same priority. > + * Must be called in process context. > + * > + * Returns true if priority is unique, false otherwise. Why this indentation? > + */ > +bool atomic_notifier_has_unique_priority(struct atomic_notifier_head *nh, > + struct notifier_block *n) > +{ > + struct notifier_block **nl = &nh->head; > + unsigned long flags; > + bool ret = true; > + > + spin_lock_irqsave(&nh->lock, flags); > + > + while ((*nl) != NULL && (*nl)->priority >= n->priority) { ' != NULL' is redundant. > + if ((*nl)->priority == n->priority && (*nl) != n) { > + ret = false; > + break; > + } > + > + nl = &((*nl)->next); > + } > + > + spin_unlock_irqrestore(&nh->lock, flags); > + > + return ret; > +} ... > + /* > + * This code gets used during boot-up, when task switching is > + * not yet working and interrupts must remain disabled. At One space is enough. > + * such times we must not call down_write(). > + */ > + while ((*nl) != NULL && (*nl)->priority >= n->priority) { ' != NULL' is not needed. > + if ((*nl)->priority == n->priority && (*nl) != n) { > + ret = false; > + break; > + } > + > + nl = &((*nl)->next); > + }
28.10.2021 14:00, Andy Shevchenko пишет: > On Thu, Oct 28, 2021 at 12:16:33AM +0300, Dmitry Osipenko wrote: >> Add atomic/blocking_notifier_has_unique_priority() helpers which return >> true if given handler has unique priority. > > ... > >> +/** >> + * atomic_notifier_has_unique_priority - Checks whether notifier's priority is unique >> + * @nh: Pointer to head of the atomic notifier chain >> + * @n: Entry in notifier chain to check >> + * >> + * Checks whether there is another notifier in the chain with the same priority. >> + * Must be called in process context. >> + * >> + * Returns true if priority is unique, false otherwise. > > Why this indentation? This is the same doc-comment style used by this file in general. I haven't tried to invent anything new. > ... > >> + /* >> + * This code gets used during boot-up, when task switching is >> + * not yet working and interrupts must remain disabled. At > > One space is enough. This comment is replicated multiple times over this source file. You can find it before each down_write(). I borrowed the text as-is, for consistency.
28.10.2021 14:00, Andy Shevchenko пишет: >> + while ((*nl) != NULL && (*nl)->priority >= n->priority) { > ' != NULL' is not needed. > I'll change it in v3, thanks.
29.10.2021 00:32, Dmitry Osipenko пишет: >>> + /* >>> + * This code gets used during boot-up, when task switching is >>> + * not yet working and interrupts must remain disabled. At >> One space is enough. > This comment is replicated multiple times over this source file. You can > find it before each down_write(). I borrowed the text as-is, for > consistency. Actually, it should be down_read() here since there are no writes. I'll correct it in v3.
diff --git a/include/linux/notifier.h b/include/linux/notifier.h index 054271e9cb20..b782ce100022 100644 --- a/include/linux/notifier.h +++ b/include/linux/notifier.h @@ -175,6 +175,11 @@ int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, bool blocking_notifier_call_chain_empty(struct blocking_notifier_head *nh); +bool atomic_notifier_has_unique_priority(struct atomic_notifier_head *nh, + struct notifier_block *nb); +bool blocking_notifier_has_unique_priority(struct blocking_notifier_head *nh, + struct notifier_block *nb); + #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 1f7ba8988b90..cf0e1c4bd364 100644 --- a/kernel/notifier.c +++ b/kernel/notifier.c @@ -203,6 +203,40 @@ int atomic_notifier_call_chain(struct atomic_notifier_head *nh, EXPORT_SYMBOL_GPL(atomic_notifier_call_chain); NOKPROBE_SYMBOL(atomic_notifier_call_chain); +/** + * atomic_notifier_has_unique_priority - Checks whether notifier's priority is unique + * @nh: Pointer to head of the atomic notifier chain + * @n: Entry in notifier chain to check + * + * Checks whether there is another notifier in the chain with the same priority. + * Must be called in process context. + * + * Returns true if priority is unique, false otherwise. + */ +bool atomic_notifier_has_unique_priority(struct atomic_notifier_head *nh, + struct notifier_block *n) +{ + struct notifier_block **nl = &nh->head; + unsigned long flags; + bool ret = true; + + spin_lock_irqsave(&nh->lock, flags); + + while ((*nl) != NULL && (*nl)->priority >= n->priority) { + if ((*nl)->priority == n->priority && (*nl) != n) { + ret = false; + break; + } + + nl = &((*nl)->next); + } + + spin_unlock_irqrestore(&nh->lock, flags); + + return ret; +} +EXPORT_SYMBOL_GPL(atomic_notifier_has_unique_priority); + /* * Blocking notifier chain routines. All access to the chain is * synchronized by an rwsem. @@ -336,6 +370,46 @@ bool blocking_notifier_call_chain_empty(struct blocking_notifier_head *nh) } EXPORT_SYMBOL_GPL(blocking_notifier_call_chain_empty); +/** + * blocking_notifier_has_unique_priority - Checks whether notifier's priority is unique + * @nh: Pointer to head of the blocking notifier chain + * @n: Entry in notifier chain to check + * + * Checks whether there is another notifier in the chain with the same priority. + * Must be called in process context. + * + * Returns true if priority is unique, false otherwise. + */ +bool blocking_notifier_has_unique_priority(struct blocking_notifier_head *nh, + struct notifier_block *n) +{ + struct notifier_block **nl = &nh->head; + bool ret = true; + + /* + * This code gets used during boot-up, when task switching is + * not yet working and interrupts must remain disabled. At + * such times we must not call down_write(). + */ + if (system_state != SYSTEM_BOOTING) + down_write(&nh->rwsem); + + while ((*nl) != NULL && (*nl)->priority >= n->priority) { + if ((*nl)->priority == n->priority && (*nl) != n) { + ret = false; + break; + } + + nl = &((*nl)->next); + } + + if (system_state != SYSTEM_BOOTING) + up_write(&nh->rwsem); + + return ret; +} +EXPORT_SYMBOL_GPL(blocking_notifier_has_unique_priority); + /* * Raw notifier chain routines. There is no protection; * the caller must provide it. Use at your own risk!
Add atomic/blocking_notifier_has_unique_priority() helpers which return true if given handler has unique priority. Signed-off-by: Dmitry Osipenko <digetx@gmail.com> --- include/linux/notifier.h | 5 +++ kernel/notifier.c | 74 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 79 insertions(+)