From: Douglas Anderson <dianders@chromium.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J . Wysocki" <rafael@kernel.org>,
Danilo Krummrich <dakr@kernel.org>,
Alan Stern <stern@rowland.harvard.edu>
Cc: Robin Murphy <robin.murphy@arm.com>,
Leon Romanovsky <leon@kernel.org>,
Paul Burton <paul.burton@mips.com>,
Saravana Kannan <saravanak@kernel.org>,
Alexander Lobakin <aleksander.lobakin@intel.com>,
Eric Dumazet <edumazet@google.com>,
Toshi Kani <toshi.kani@hp.com>, Christoph Hellwig <hch@lst.de>,
Alexey Kardashevskiy <aik@ozlabs.ru>,
Johan Hovold <johan@kernel.org>,
Douglas Anderson <dianders@chromium.org>,
ardb@kernel.org, broonie@kernel.org, catalin.marinas@arm.com,
chleroy@kernel.org, david@kernel.org,
driver-core@lists.linux.dev, kees@kernel.org,
kevin.brodsky@arm.com, lenb@kernel.org,
linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
maddy@linux.ibm.com, maz@kernel.org, miko.lenczewski@arm.com,
mpe@ellerman.id.au, npiggin@gmail.com, osalvador@suse.de,
oupton@kernel.org, peterz@infradead.org, tglx@kernel.org,
will@kernel.org, yangyicong@hisilicon.com, yeoreum.yun@arm.com
Subject: [PATCH v3 9/9] driver core: Replace dev->offline + ->offline_disabled with DEV_FLAGs
Date: Thu, 2 Apr 2026 17:49:55 -0700 [thread overview]
Message-ID: <20260402174925.v3.9.I897d478b4a9361d79cd5073207c1062fd4d0d0e4@changeid> (raw)
In-Reply-To: <20260403005005.30424-1-dianders@chromium.org>
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@kernel.org>
Cc: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
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 v3:
- New
arch/arm64/kernel/cpufeature.c | 2 +-
.../platforms/pseries/hotplug-memory.c | 4 ++--
drivers/acpi/scan.c | 3 ++-
drivers/base/core.c | 19 ++++++++++---------
drivers/base/cpu.c | 4 ++--
drivers/base/memory.c | 2 +-
include/linux/device.h | 9 ++++-----
kernel/cpu.c | 4 ++--
8 files changed, 24 insertions(+), 23 deletions(-)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 32c2dbcc0c64..f6f7c35b7a93 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;
+ set_bit(DEV_FLAG_OFFLINE_DISABLED, &get_cpu_device(lucky_winner)->flags);
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..d9a0a75ada46 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 && test_bit(DEV_FLAG_OFFLINE, &mem_block->dev.flags))
rc = device_online(&mem_block->dev);
- else if (!online && !mem_block->dev.offline)
+ else if (!online && !test_bit(DEV_FLAG_OFFLINE, &mem_block->dev.flags))
rc = device_offline(&mem_block->dev);
else
rc = 0;
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index e8cdbdb46fdb..f2707b704468 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -122,7 +122,8 @@ 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) &&
+ !test_bit(DEV_FLAG_OFFLINE, &pn->dev->flags)) {
if (uevent)
kobject_uevent_env(&pn->dev->kobj, KOBJ_CHANGE, envp);
diff --git a/drivers/base/core.c b/drivers/base/core.c
index a87bd40499b6..63d724ece384 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2789,7 +2789,7 @@ static ssize_t online_show(struct device *dev, struct device_attribute *attr,
bool val;
device_lock(dev);
- val = !dev->offline;
+ val = !test_bit(DEV_FLAG_OFFLINE, &dev->flags);
device_unlock(dev);
return sysfs_emit(buf, "%u\n", val);
}
@@ -2914,7 +2914,7 @@ 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) && !test_bit(DEV_FLAG_OFFLINE_DISABLED, &dev->flags)) {
error = device_create_file(dev, &dev_attr_online);
if (error)
goto err_remove_dev_groups;
@@ -4179,7 +4179,8 @@ 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) &&
+ !test_bit(DEV_FLAG_OFFLINE, &dev->flags) ? -EBUSY : 0;
}
/**
@@ -4197,7 +4198,7 @@ int device_offline(struct device *dev)
{
int ret;
- if (dev->offline_disabled)
+ if (test_bit(DEV_FLAG_OFFLINE_DISABLED, &dev->flags))
return -EPERM;
ret = device_for_each_child(dev, NULL, device_check_offline);
@@ -4206,13 +4207,13 @@ int device_offline(struct device *dev)
device_lock(dev);
if (device_supports_offline(dev)) {
- if (dev->offline) {
+ if (test_bit(DEV_FLAG_OFFLINE, &dev->flags)) {
ret = 1;
} else {
ret = dev->bus->offline(dev);
if (!ret) {
kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
- dev->offline = true;
+ set_bit(DEV_FLAG_OFFLINE, &dev->flags);
}
}
}
@@ -4237,11 +4238,11 @@ int device_online(struct device *dev)
device_lock(dev);
if (device_supports_offline(dev)) {
- if (dev->offline) {
+ if (test_bit(DEV_FLAG_OFFLINE, &dev->flags)) {
ret = dev->bus->online(dev);
if (!ret) {
kobject_uevent(&dev->kobj, KOBJ_ONLINE);
- dev->offline = false;
+ clear_bit(DEV_FLAG_OFFLINE, &dev->flags);
}
} else {
ret = 1;
@@ -4715,7 +4716,7 @@ 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) && !test_bit(DEV_FLAG_OFFLINE_DISABLED, &dev->flags)) {
/* 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..e4e6a399def4 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);
+ assign_bit(DEV_FLAG_OFFLINE_DISABLED, &cpu->dev.flags, !cpu->hotpluggable);
+ assign_bit(DEV_FLAG_OFFLINE, &cpu->dev.flags, !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..7f42727dde81 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;
+ assign_bit(DEV_FLAG_OFFLINE, &memory->dev.flags, memory->state == MEM_OFFLINE);
ret = device_register(&memory->dev);
if (ret) {
diff --git a/include/linux/device.h b/include/linux/device.h
index f6ca067bacca..fd53aa04cad9 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -484,6 +484,8 @@ 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,
@@ -494,6 +496,8 @@ enum struct_device_flags {
DEV_FLAG_STATE_SYNCED,
DEV_FLAG_DMA_COHERENT,
DEV_FLAG_OF_NODE_REUSED,
+ DEV_FLAG_OFFLINE_DISABLED,
+ DEV_FLAG_OFFLINE,
};
/**
@@ -571,8 +575,6 @@ enum struct_device_flags {
* 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
@@ -677,9 +679,6 @@ struct device {
enum device_removable removable;
- bool offline_disabled:1;
- bool offline:1;
-
unsigned long flags;
};
diff --git a/kernel/cpu.c b/kernel/cpu.c
index bc4f7a9ba64e..15a873ad8025 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;
+ set_bit(DEV_FLAG_OFFLINE, &dev->flags);
/* 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;
+ clear_bit(DEV_FLAG_OFFLINE, &dev->flags);
/* Tell user space about the state change */
kobject_uevent(&dev->kobj, KOBJ_ONLINE);
}
--
2.53.0.1213.gd9a14994de-goog
next prev parent reply other threads:[~2026-04-03 0:52 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-03 0:49 [PATCH v3 0/9] driver core: Fix some race conditions Douglas Anderson
2026-04-03 0:49 ` [PATCH v3 4/9] driver core: Replace dev->dma_skip_sync with DEV_FLAG_DMA_SKIP_SYNC Douglas Anderson
2026-04-03 0:49 ` Douglas Anderson [this message]
2026-04-03 11:56 ` [PATCH v3 9/9] driver core: Replace dev->offline + ->offline_disabled with DEV_FLAGs Mark Brown
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