[PATCH v4 9/9] driver core: Replace dev->offline + ->offline_disabled with accessors
From: Douglas Anderson
Date: Fri Apr 03 2026 - 20:13:02 EST
In C, bitfields are not necessarily safe to modify from multiple
threads without locking. Switch "offline" and "offline_disabled" over
to the "flags" field so modifications are safe.
Cc: Rafael J. Wysocki <rafael@xxxxxxxxxx>
Acked-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---
Not fixing any known bugs; problem is theoretical and found by code
inspection. Change is done somewhat manually and only lightly tested
(mostly compile-time tested).
Changes in v4:
- Use accessor functions for flags
Changes in v3:
- New
arch/arm64/kernel/cpufeature.c | 2 +-
.../powerpc/platforms/pseries/hotplug-memory.c | 4 ++--
drivers/acpi/scan.c | 2 +-
drivers/base/core.c | 18 +++++++++---------
drivers/base/cpu.c | 4 ++--
drivers/base/memory.c | 2 +-
include/linux/device.h | 12 ++++++------
kernel/cpu.c | 4 ++--
8 files changed, 24 insertions(+), 24 deletions(-)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 32c2dbcc0c64..c832aa565dc2 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -4042,7 +4042,7 @@ static int enable_mismatched_32bit_el0(unsigned int cpu)
*/
lucky_winner = cpu_32bit ? cpu : cpumask_any_and(cpu_32bit_el0_mask,
cpu_active_mask);
- get_cpu_device(lucky_winner)->offline_disabled = true;
+ dev_set_offline_disabled(get_cpu_device(lucky_winner));
setup_elf_hwcaps(compat_elf_hwcaps);
elf_hwcap_fixup();
pr_info("Asymmetric 32-bit EL0 support detected on CPU %u; CPU hot-unplug disabled on CPU %u\n",
diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
index b2f14db59034..75f85a5da981 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -213,9 +213,9 @@ static int dlpar_change_lmb_state(struct drmem_lmb *lmb, bool online)
return -EINVAL;
}
- if (online && mem_block->dev.offline)
+ if (online && dev_offline(&mem_block->dev))
rc = device_online(&mem_block->dev);
- else if (!online && !mem_block->dev.offline)
+ else if (!online && !dev_offline(&mem_block->dev))
rc = device_offline(&mem_block->dev);
else
rc = 0;
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index e8cdbdb46fdb..1353adbcc234 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -122,7 +122,7 @@ bool acpi_scan_is_offline(struct acpi_device *adev, bool uevent)
mutex_lock_nested(&adev->physical_node_lock, SINGLE_DEPTH_NESTING);
list_for_each_entry(pn, &adev->physical_node_list, node)
- if (device_supports_offline(pn->dev) && !pn->dev->offline) {
+ if (device_supports_offline(pn->dev) && !dev_offline(pn->dev)) {
if (uevent)
kobject_uevent_env(&pn->dev->kobj, KOBJ_CHANGE, envp);
diff --git a/drivers/base/core.c b/drivers/base/core.c
index f12f3b53b4d0..79c85dbcffad 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2788,7 +2788,7 @@ static ssize_t online_show(struct device *dev, struct device_attribute *attr,
bool val;
device_lock(dev);
- val = !dev->offline;
+ val = !dev_offline(dev);
device_unlock(dev);
return sysfs_emit(buf, "%u\n", val);
}
@@ -2913,7 +2913,7 @@ static int device_add_attrs(struct device *dev)
if (error)
goto err_remove_type_groups;
- if (device_supports_offline(dev) && !dev->offline_disabled) {
+ if (device_supports_offline(dev) && !dev_offline_disabled(dev)) {
error = device_create_file(dev, &dev_attr_online);
if (error)
goto err_remove_dev_groups;
@@ -4178,7 +4178,7 @@ static int device_check_offline(struct device *dev, void *not_used)
if (ret)
return ret;
- return device_supports_offline(dev) && !dev->offline ? -EBUSY : 0;
+ return device_supports_offline(dev) && !dev_offline(dev) ? -EBUSY : 0;
}
/**
@@ -4196,7 +4196,7 @@ int device_offline(struct device *dev)
{
int ret;
- if (dev->offline_disabled)
+ if (dev_offline_disabled(dev))
return -EPERM;
ret = device_for_each_child(dev, NULL, device_check_offline);
@@ -4205,13 +4205,13 @@ int device_offline(struct device *dev)
device_lock(dev);
if (device_supports_offline(dev)) {
- if (dev->offline) {
+ if (dev_offline(dev)) {
ret = 1;
} else {
ret = dev->bus->offline(dev);
if (!ret) {
kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
- dev->offline = true;
+ dev_set_offline(dev);
}
}
}
@@ -4236,11 +4236,11 @@ int device_online(struct device *dev)
device_lock(dev);
if (device_supports_offline(dev)) {
- if (dev->offline) {
+ if (dev_offline(dev)) {
ret = dev->bus->online(dev);
if (!ret) {
kobject_uevent(&dev->kobj, KOBJ_ONLINE);
- dev->offline = false;
+ dev_clear_offline(dev);
}
} else {
ret = 1;
@@ -4714,7 +4714,7 @@ static int device_attrs_change_owner(struct device *dev, kuid_t kuid,
if (error)
return error;
- if (device_supports_offline(dev) && !dev->offline_disabled) {
+ if (device_supports_offline(dev) && !dev_offline_disabled(dev)) {
/* Change online device attributes of @dev to @kuid/@kgid. */
error = sysfs_file_change_owner(kobj, dev_attr_online.attr.name,
kuid, kgid);
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 875abdc9942e..19d288a3c80c 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -422,8 +422,8 @@ int register_cpu(struct cpu *cpu, int num)
cpu->dev.id = num;
cpu->dev.bus = &cpu_subsys;
cpu->dev.release = cpu_device_release;
- cpu->dev.offline_disabled = !cpu->hotpluggable;
- cpu->dev.offline = !cpu_online(num);
+ dev_assign_offline_disabled(&cpu->dev, !cpu->hotpluggable);
+ dev_assign_offline(&cpu->dev, !cpu_online(num));
cpu->dev.of_node = of_get_cpu_node(num, NULL);
cpu->dev.groups = common_cpu_attr_groups;
if (cpu->hotpluggable)
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index a3091924918b..5005654f44fa 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -697,7 +697,7 @@ static int __add_memory_block(struct memory_block *memory)
memory->dev.id = memory->start_section_nr / sections_per_block;
memory->dev.release = memory_block_release;
memory->dev.groups = memory_memblk_attr_groups;
- memory->dev.offline = memory->state == MEM_OFFLINE;
+ dev_assign_offline(&memory->dev, memory->state == MEM_OFFLINE);
ret = device_register(&memory->dev);
if (ret) {
diff --git a/include/linux/device.h b/include/linux/device.h
index 8132aab17e04..65fc6c566cc6 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -485,6 +485,8 @@ struct device_physical_location {
* architecture supports non-coherent devices.
* @DEV_FLAG_OF_NODE_REUSED: Set if the device-tree node is shared with an
* ancestor device.
+ * @DEV_FLAG_OFFLINE_DISABLED: If set, the device is permanently online.
+ * @DEV_FLAG_OFFLINE: Set after successful invocation of bus type's .offline().
*/
enum struct_device_flags {
DEV_FLAG_READY_TO_PROBE = 0,
@@ -495,6 +497,8 @@ enum struct_device_flags {
DEV_FLAG_STATE_SYNCED = 5,
DEV_FLAG_DMA_COHERENT = 6,
DEV_FLAG_OF_NODE_REUSED = 7,
+ DEV_FLAG_OFFLINE_DISABLED = 8,
+ DEV_FLAG_OFFLINE = 9,
DEV_FLAG_COUNT
};
@@ -573,9 +577,6 @@ enum struct_device_flags {
* @removable: Whether the device can be removed from the system. This
* should be set by the subsystem / bus driver that discovered
* the device.
- *
- * @offline_disabled: If set, the device is permanently online.
- * @offline: Set after successful invocation of bus type's .offline().
* @flags: DEV_FLAG_XXX flags. Use atomic bitfield operations to modify.
*
* At the lowest level, every device in a Linux system is represented by an
@@ -680,9 +681,6 @@ struct device {
enum device_removable removable;
- bool offline_disabled:1;
- bool offline:1;
-
DECLARE_BITMAP(flags, DEV_FLAG_COUNT);
};
@@ -716,6 +714,8 @@ __create_dev_flag_accessors(dma_ops_bypass, DEV_FLAG_DMA_OPS_BYPASS);
__create_dev_flag_accessors(state_synced, DEV_FLAG_STATE_SYNCED);
__create_dev_flag_accessors(dma_coherent, DEV_FLAG_DMA_COHERENT);
__create_dev_flag_accessors(of_node_reused, DEV_FLAG_OF_NODE_REUSED);
+__create_dev_flag_accessors(offline_disabled, DEV_FLAG_OFFLINE_DISABLED);
+__create_dev_flag_accessors(offline, DEV_FLAG_OFFLINE);
/**
* struct device_link - Device link representation.
diff --git a/kernel/cpu.c b/kernel/cpu.c
index bc4f7a9ba64e..f975bb34915b 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2639,7 +2639,7 @@ static void cpuhp_offline_cpu_device(unsigned int cpu)
{
struct device *dev = get_cpu_device(cpu);
- dev->offline = true;
+ dev_set_offline(dev);
/* Tell user space about the state change */
kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
}
@@ -2648,7 +2648,7 @@ static void cpuhp_online_cpu_device(unsigned int cpu)
{
struct device *dev = get_cpu_device(cpu);
- dev->offline = false;
+ dev_clear_offline(dev);
/* Tell user space about the state change */
kobject_uevent(&dev->kobj, KOBJ_ONLINE);
}
--
2.53.0.1213.gd9a14994de-goog