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[PATCH v7 01/20] notifier: Add blocking_notifier_call_chain_is_empty()
- To: Thierry Reding <thierry.reding@xxxxxxxxx>, Jonathan Hunter <jonathanh@xxxxxxxxxx>, Russell King <linux@xxxxxxxxxxxxxxx>, Catalin Marinas <catalin.marinas@xxxxxxx>, Will Deacon <will@xxxxxxxxxx>, Guo Ren <guoren@xxxxxxxxxx>, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>, Greg Ungerer <gerg@xxxxxxxxxxxxxx>, Joshua Thompson <funaho@xxxxxxxxx>, Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>, Sebastian Reichel <sre@xxxxxxxxxx>, Linus Walleij <linus.walleij@xxxxxxxxxx>, Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>, Greentime Hu <green.hu@xxxxxxxxx>, Vincent Chen <deanbo422@xxxxxxxxx>, "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>, Helge Deller <deller@xxxxxx>, Michael Ellerman <mpe@xxxxxxxxxxxxxx>, Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>, Paul Mackerras <paulus@xxxxxxxxx>, Paul Walmsley <paul.walmsley@xxxxxxxxxx>, Palmer Dabbelt <palmer@xxxxxxxxxxx>, Albert Ou <aou@xxxxxxxxxxxxxxxxx>, Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>, Rich Felker <dalias@xxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, x86@xxxxxxxxxx, "H. Peter Anvin" <hpa@xxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, "Rafael J. Wysocki" <rafael@xxxxxxxxxx>, Len Brown <lenb@xxxxxxxxxx>, Santosh Shilimkar <ssantosh@xxxxxxxxxx>, Krzysztof Kozlowski <krzk@xxxxxxxxxx>, Liam Girdwood <lgirdwood@xxxxxxxxx>, Mark Brown <broonie@xxxxxxxxxx>, Pavel Machek <pavel@xxxxxx>, Lee Jones <lee.jones@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Guenter Roeck <linux@xxxxxxxxxxxx>, Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>, Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>, Ulf Hansson <ulf.hansson@xxxxxxxxxx>, Michał Mirosław <mirq-linux@xxxxxxxxxxxx>
- From: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
- Date: Tue, 12 Apr 2022 02:38:13 +0300
- Cc: linux-kernel@xxxxxxxxxxxxxxx, linux-csky@xxxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, linux-m68k@xxxxxxxxxxxxxxxxxxxx, linux-mips@xxxxxxxxxxxxxxx, linux-parisc@xxxxxxxxxxxxxxx, linux-riscv@xxxxxxxxxxxxxxxxxxx, linux-sh@xxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-acpi@xxxxxxxxxxxxxxx, linux-pm@xxxxxxxxxxxxxxx, linux-tegra@xxxxxxxxxxxxxxx
- Delivery-date: Tue, 12 Apr 2022 05:11:56 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Add blocking_notifier_call_chain_is_empty() that returns true if call
chain is empty.
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
---
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..d4717bc0ab85 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 blocking_notifier_call_chain_is_empty(struct
blocking_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..4ed6bda8f127 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -323,6 +323,19 @@ int blocking_notifier_call_chain(struct
blocking_notifier_head *nh,
}
EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
+/**
+ * blocking_notifier_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 blocking_notifier_call_chain_is_empty(struct blocking_notifier_head *nh)
+{
+ return !rcu_access_pointer(nh->head);
+}
+
/*
* Raw notifier chain routines. There is no protection;
* the caller must provide it. Use at your own risk!
--
2.35.1
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