[PATCH v2 0/2] jump_label: drop some workarounds in static key initialization

[PATCH v2 0/2] jump_label: drop some workarounds in static key initialization

[Thomas Weißschuh]

These workarounds are not necessary anymore so remove them.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
Changes in v2:
- Rebase on v7.0-rc1.
- Link to v1: https://lore.kernel.org/r/20251118-jump_label-cleanup-v1-0-440a424d7282@linutronix.de

---
Thomas Weißschuh (2):
      jump_label: use ATOMIC_INIT() for initialization of .enabled
      jump_label: remove workaround for old compilers in initializations

 include/linux/jump_label.h | 22 ++++------------------
 kernel/jump_label.c        |  9 ---------
 2 files changed, 4 insertions(+), 27 deletions(-)
---
base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
change-id: 20251110-jump_label-cleanup-d7036bd1e533

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@linutronix.de>

[PATCH v2 1/2] jump_label: use ATOMIC_INIT() for initialization of .enabled

[Thomas Weißschuh]

Currently ATOMIC_INIT() is not used because in the past that macro was
provided by linux/atomic.h which is not usable from linux/jump_label.h.
However since commit 7ca8cf5347f7 ("locking/atomic: Move ATOMIC_INIT
into linux/types.h") the macro only requires linux/types.h.

Remove the now unnecessary workaround and the associated assertions.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
 include/linux/jump_label.h | 11 ++---------
 kernel/jump_label.c        |  9 ---------
 2 files changed, 2 insertions(+), 18 deletions(-)

diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index fdb79dd1ebd8..e494b360d36d 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -238,18 +238,11 @@ extern void static_key_enable_cpuslocked(struct static_key *key);
 extern void static_key_disable_cpuslocked(struct static_key *key);
 extern enum jump_label_type jump_label_init_type(struct jump_entry *entry);
 
-/*
- * We should be using ATOMIC_INIT() for initializing .enabled, but
- * the inclusion of atomic.h is problematic for inclusion of jump_label.h
- * in 'low-level' headers. Thus, we are initializing .enabled with a
- * raw value, but have added a BUILD_BUG_ON() to catch any issues in
- * jump_label_init() see: kernel/jump_label.c.
- */
 #define STATIC_KEY_INIT_TRUE					\
-	{ .enabled = { 1 },					\
+	{ .enabled = ATOMIC_INIT(1),				\
 	  { .type = JUMP_TYPE_TRUE } }
 #define STATIC_KEY_INIT_FALSE					\
-	{ .enabled = { 0 },					\
+	{ .enabled = ATOMIC_INIT(0),				\
 	  { .type = JUMP_TYPE_FALSE } }
 
 #else  /* !CONFIG_JUMP_LABEL */
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 7cb19e601426..e851e4b37d0e 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -529,15 +529,6 @@ void __init jump_label_init(void)
 	struct static_key *key = NULL;
 	struct jump_entry *iter;
 
-	/*
-	 * Since we are initializing the static_key.enabled field with
-	 * with the 'raw' int values (to avoid pulling in atomic.h) in
-	 * jump_label.h, let's make sure that is safe. There are only two
-	 * cases to check since we initialize to 0 or 1.
-	 */
-	BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
-	BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
-
 	if (static_key_initialized)
 		return;
 

-- 
2.53.0

[PATCH v2 2/2] jump_label: remove workaround for old compilers in initializations

[Thomas Weißschuh]

The extra braces for the initialization of the anonymous union members
were added in commit cd8d860dcce9 ("jump_label: Fix anonymous union
initialization") to compensate for limitations in gcc < 4.6.

Versions of gcc this old are not supported anymore,
so drop the workaround.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
 include/linux/jump_label.h | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index e494b360d36d..b9c7b0ebf7b9 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -87,13 +87,6 @@ struct static_key {
 	atomic_t enabled;
 #ifdef CONFIG_JUMP_LABEL
 /*
- * Note:
- *   To make anonymous unions work with old compilers, the static
- *   initialization of them requires brackets. This creates a dependency
- *   on the order of the struct with the initializers. If any fields
- *   are added, STATIC_KEY_INIT_TRUE and STATIC_KEY_INIT_FALSE may need
- *   to be modified.
- *
  * bit 0 => 1 if key is initially true
  *	    0 if initially false
  * bit 1 => 1 if points to struct static_key_mod
@@ -240,10 +233,10 @@ extern enum jump_label_type jump_label_init_type(struct jump_entry *entry);
 
 #define STATIC_KEY_INIT_TRUE					\
 	{ .enabled = ATOMIC_INIT(1),				\
-	  { .type = JUMP_TYPE_TRUE } }
+	  .type = JUMP_TYPE_TRUE }
 #define STATIC_KEY_INIT_FALSE					\
 	{ .enabled = ATOMIC_INIT(0),				\
-	  { .type = JUMP_TYPE_FALSE } }
+	  .type = JUMP_TYPE_FALSE }
 
 #else  /* !CONFIG_JUMP_LABEL */
 

-- 
2.53.0

Re: [PATCH v2 0/2] jump_label: drop some workarounds in static key initialization

[Peter Zijlstra]

On Fri, Mar 13, 2026 at 09:22:17AM +0100, Thomas Weißschuh wrote:
> These workarounds are not necessary anymore so remove them.

> Thomas Weißschuh (2):
>       jump_label: use ATOMIC_INIT() for initialization of .enabled
>       jump_label: remove workaround for old compilers in initializations

Excellent, thanks!

[tip: locking/core] jump_label: remove workaround for old compilers in initializations

[tip-bot2 for Thomas Weißschuh]

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     acb38872d4cbec5b6825345d9d757e21d2d9d953
Gitweb:        https://git.kernel.org/tip/acb38872d4cbec5b6825345d9d757e21d2d9d953
Author:        Thomas Weißschuh <thomas.weissschuh@linutronix.de>
AuthorDate:    Fri, 13 Mar 2026 09:22:19 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 16 Mar 2026 13:16:49 +01:00

jump_label: remove workaround for old compilers in initializations

The extra braces for the initialization of the anonymous union members
were added in commit cd8d860dcce9 ("jump_label: Fix anonymous union
initialization") to compensate for limitations in gcc < 4.6.

Versions of gcc this old are not supported anymore,
so drop the workaround.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260313-jump_label-cleanup-v2-2-35d3c0bde549@linutronix.de
---
 include/linux/jump_label.h | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index e494b36..b9c7b0e 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -87,13 +87,6 @@ struct static_key {
 	atomic_t enabled;
 #ifdef CONFIG_JUMP_LABEL
 /*
- * Note:
- *   To make anonymous unions work with old compilers, the static
- *   initialization of them requires brackets. This creates a dependency
- *   on the order of the struct with the initializers. If any fields
- *   are added, STATIC_KEY_INIT_TRUE and STATIC_KEY_INIT_FALSE may need
- *   to be modified.
- *
  * bit 0 => 1 if key is initially true
  *	    0 if initially false
  * bit 1 => 1 if points to struct static_key_mod
@@ -240,10 +233,10 @@ extern enum jump_label_type jump_label_init_type(struct jump_entry *entry);
 
 #define STATIC_KEY_INIT_TRUE					\
 	{ .enabled = ATOMIC_INIT(1),				\
-	  { .type = JUMP_TYPE_TRUE } }
+	  .type = JUMP_TYPE_TRUE }
 #define STATIC_KEY_INIT_FALSE					\
 	{ .enabled = ATOMIC_INIT(0),				\
-	  { .type = JUMP_TYPE_FALSE } }
+	  .type = JUMP_TYPE_FALSE }
 
 #else  /* !CONFIG_JUMP_LABEL */
 

[tip: locking/core] jump_label: use ATOMIC_INIT() for initialization of .enabled

[tip-bot2 for Thomas Weißschuh]

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     428c56525bf5dbc3bd5e30014df1f5213f8bd7c8
Gitweb:        https://git.kernel.org/tip/428c56525bf5dbc3bd5e30014df1f5213f8bd7c8
Author:        Thomas Weißschuh <thomas.weissschuh@linutronix.de>
AuthorDate:    Fri, 13 Mar 2026 09:22:18 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 16 Mar 2026 13:16:48 +01:00

jump_label: use ATOMIC_INIT() for initialization of .enabled

Currently ATOMIC_INIT() is not used because in the past that macro was
provided by linux/atomic.h which is not usable from linux/jump_label.h.
However since commit 7ca8cf5347f7 ("locking/atomic: Move ATOMIC_INIT
into linux/types.h") the macro only requires linux/types.h.

Remove the now unnecessary workaround and the associated assertions.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260313-jump_label-cleanup-v2-1-35d3c0bde549@linutronix.de
---
 include/linux/jump_label.h | 11 ++---------
 kernel/jump_label.c        |  9 ---------
 2 files changed, 2 insertions(+), 18 deletions(-)

diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index fdb79dd..e494b36 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -238,18 +238,11 @@ extern void static_key_enable_cpuslocked(struct static_key *key);
 extern void static_key_disable_cpuslocked(struct static_key *key);
 extern enum jump_label_type jump_label_init_type(struct jump_entry *entry);
 
-/*
- * We should be using ATOMIC_INIT() for initializing .enabled, but
- * the inclusion of atomic.h is problematic for inclusion of jump_label.h
- * in 'low-level' headers. Thus, we are initializing .enabled with a
- * raw value, but have added a BUILD_BUG_ON() to catch any issues in
- * jump_label_init() see: kernel/jump_label.c.
- */
 #define STATIC_KEY_INIT_TRUE					\
-	{ .enabled = { 1 },					\
+	{ .enabled = ATOMIC_INIT(1),				\
 	  { .type = JUMP_TYPE_TRUE } }
 #define STATIC_KEY_INIT_FALSE					\
-	{ .enabled = { 0 },					\
+	{ .enabled = ATOMIC_INIT(0),				\
 	  { .type = JUMP_TYPE_FALSE } }
 
 #else  /* !CONFIG_JUMP_LABEL */
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 7cb19e6..e851e4b 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -529,15 +529,6 @@ void __init jump_label_init(void)
 	struct static_key *key = NULL;
 	struct jump_entry *iter;
 
-	/*
-	 * Since we are initializing the static_key.enabled field with
-	 * with the 'raw' int values (to avoid pulling in atomic.h) in
-	 * jump_label.h, let's make sure that is safe. There are only two
-	 * cases to check since we initialize to 0 or 1.
-	 */
-	BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
-	BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
-
 	if (static_key_initialized)
 		return;