On Tuesday, July 23, 2013 04:09:43 PM Lv Zheng wrote:
> This patch adds reference couting for ACPI operation region handlers to fix
> races caused by the ACPICA address space callback invocations.
>
> ACPICA address space callback invocation is not suitable for Linux
> CONFIG_MODULE=y execution environment. This patch tries to protect the
> address space callbacks by invoking them under a module safe environment.
> The IPMI address space handler is also upgraded in this patch.
> The acpi_unregister_region() is designed to meet the following
> requirements:
> 1. It acts as a barrier for operation region callbacks - no callback will
> happen after acpi_unregister_region().
> 2. acpi_unregister_region() is safe to be called in moudle->exit()
> functions.
> Using reference counting rather than module referencing allows
> such benefits to be achieved even when acpi_unregister_region() is called
> in the environments other than module->exit().
> The header file of include/acpi/acpi_bus.h should contain the declarations
> that have references to some ACPICA defined types.
>
> Signed-off-by: Lv Zheng <lv.zh...@intel.com>
> Reviewed-by: Huang Ying <ying.hu...@intel.com>
> ---
> drivers/acpi/acpi_ipmi.c | 16 ++--
> drivers/acpi/osl.c | 224
> ++++++++++++++++++++++++++++++++++++++++++++++
> include/acpi/acpi_bus.h | 5 ++
> 3 files changed, 235 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/acpi/acpi_ipmi.c b/drivers/acpi/acpi_ipmi.c
> index 5f8f495..2a09156 100644
> --- a/drivers/acpi/acpi_ipmi.c
> +++ b/drivers/acpi/acpi_ipmi.c
> @@ -539,20 +539,18 @@ out_ref:
> static int __init acpi_ipmi_init(void)
> {
> int result = 0;
> - acpi_status status;
>
> if (acpi_disabled)
> return result;
>
> mutex_init(&driver_data.ipmi_lock);
>
> - status = acpi_install_address_space_handler(ACPI_ROOT_OBJECT,
> - ACPI_ADR_SPACE_IPMI,
> - &acpi_ipmi_space_handler,
> - NULL, NULL);
> - if (ACPI_FAILURE(status)) {
> + result = acpi_register_region(ACPI_ADR_SPACE_IPMI,
> + &acpi_ipmi_space_handler,
> + NULL, NULL);
> + if (result) {
> pr_warn("Can't register IPMI opregion space handle\n");
> - return -EINVAL;
> + return result;
> }
>
> result = ipmi_smi_watcher_register(&driver_data.bmc_events);
> @@ -596,9 +594,7 @@ static void __exit acpi_ipmi_exit(void)
> }
> mutex_unlock(&driver_data.ipmi_lock);
>
> - acpi_remove_address_space_handler(ACPI_ROOT_OBJECT,
> - ACPI_ADR_SPACE_IPMI,
> - &acpi_ipmi_space_handler);
> + acpi_unregister_region(ACPI_ADR_SPACE_IPMI);
> }
>
> module_init(acpi_ipmi_init);
> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> index 6ab2c35..8398e51 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -86,6 +86,42 @@ static struct workqueue_struct *kacpid_wq;
> static struct workqueue_struct *kacpi_notify_wq;
> static struct workqueue_struct *kacpi_hotplug_wq;
>
> +struct acpi_region {
> + unsigned long flags;
> +#define ACPI_REGION_DEFAULT 0x01
> +#define ACPI_REGION_INSTALLED 0x02
> +#define ACPI_REGION_REGISTERED 0x04
> +#define ACPI_REGION_UNREGISTERING 0x08
> +#define ACPI_REGION_INSTALLING 0x10
What about (1UL << 1), (1UL << 2) etc.?
Also please remove the #defines out of the struct definition.
> + /*
> + * NOTE: Upgrading All Region Handlers
> + * This flag is only used during the period where not all of the
> + * region handers are upgraded to the new interfaces.
> + */
> +#define ACPI_REGION_MANAGED 0x80
> + acpi_adr_space_handler handler;
> + acpi_adr_space_setup setup;
> + void *context;
> + /* Invoking references */
> + atomic_t refcnt;
Actually, why don't you use krefs?
> +};
> +
> +static struct acpi_region acpi_regions[ACPI_NUM_PREDEFINED_REGIONS] = {
> + [ACPI_ADR_SPACE_SYSTEM_MEMORY] = {
> + .flags = ACPI_REGION_DEFAULT,
> + },
> + [ACPI_ADR_SPACE_SYSTEM_IO] = {
> + .flags = ACPI_REGION_DEFAULT,
> + },
> + [ACPI_ADR_SPACE_PCI_CONFIG] = {
> + .flags = ACPI_REGION_DEFAULT,
> + },
> + [ACPI_ADR_SPACE_IPMI] = {
> + .flags = ACPI_REGION_MANAGED,
> + },
> +};
> +static DEFINE_MUTEX(acpi_mutex_region);
> +
> /*
> * This list of permanent mappings is for memory that may be accessed from
> * interrupt context, where we can't do the ioremap().
> @@ -1799,3 +1835,191 @@ void alloc_acpi_hp_work(acpi_handle handle, u32 type,
> void *context,
> kfree(hp_work);
> }
> EXPORT_SYMBOL_GPL(alloc_acpi_hp_work);
> +
> +static bool acpi_region_managed(struct acpi_region *rgn)
> +{
> + /*
> + * NOTE: Default and Managed
> + * We only need to avoid region management on the regions managed
> + * by ACPICA (ACPI_REGION_DEFAULT). Currently, we need additional
> + * check as many operation region handlers are not upgraded, so
> + * only those known to be safe are managed (ACPI_REGION_MANAGED).
> + */
> + return !(rgn->flags & ACPI_REGION_DEFAULT) &&
> + (rgn->flags & ACPI_REGION_MANAGED);
> +}
> +
> +static bool acpi_region_callable(struct acpi_region *rgn)
> +{
> + return (rgn->flags & ACPI_REGION_REGISTERED) &&
> + !(rgn->flags & ACPI_REGION_UNREGISTERING);
> +}
> +
> +static acpi_status
> +acpi_region_default_handler(u32 function,
> + acpi_physical_address address,
> + u32 bit_width, u64 *value,
> + void *handler_context, void *region_context)
> +{
> + acpi_adr_space_handler handler;
> + struct acpi_region *rgn = (struct acpi_region *)handler_context;
> + void *context;
> + acpi_status status = AE_NOT_EXIST;
> +
> + mutex_lock(&acpi_mutex_region);
> + if (!acpi_region_callable(rgn) || !rgn->handler) {
> + mutex_unlock(&acpi_mutex_region);
> + return status;
> + }
> +
> + atomic_inc(&rgn->refcnt);
> + handler = rgn->handler;
> + context = rgn->context;
> + mutex_unlock(&acpi_mutex_region);
> +
> + status = handler(function, address, bit_width, value, context,
> + region_context);
Why don't we call the handler under the mutex?
What exactly prevents context from becoming NULL before the call above?
> + atomic_dec(&rgn->refcnt);
> +
> + return status;
> +}
> +
> +static acpi_status
> +acpi_region_default_setup(acpi_handle handle, u32 function,
> + void *handler_context, void **region_context)
> +{
> + acpi_adr_space_setup setup;
> + struct acpi_region *rgn = (struct acpi_region *)handler_context;
> + void *context;
> + acpi_status status = AE_OK;
> +
> + mutex_lock(&acpi_mutex_region);
> + if (!acpi_region_callable(rgn) || !rgn->setup) {
> + mutex_unlock(&acpi_mutex_region);
> + return status;
> + }
> +
> + atomic_inc(&rgn->refcnt);
> + setup = rgn->setup;
> + context = rgn->context;
> + mutex_unlock(&acpi_mutex_region);
> +
> + status = setup(handle, function, context, region_context);
Can setup drop rgn->refcnt ?
> + atomic_dec(&rgn->refcnt);
> +
> + return status;
> +}
> +
> +static int __acpi_install_region(struct acpi_region *rgn,
> + acpi_adr_space_type space_id)
> +{
> + int res = 0;
> + acpi_status status;
> + int installing = 0;
> +
> + mutex_lock(&acpi_mutex_region);
> + if (rgn->flags & ACPI_REGION_INSTALLED)
> + goto out_lock;
> + if (rgn->flags & ACPI_REGION_INSTALLING) {
> + res = -EBUSY;
> + goto out_lock;
> + }
> +
> + installing = 1;
> + rgn->flags |= ACPI_REGION_INSTALLING;
> + status = acpi_install_address_space_handler(ACPI_ROOT_OBJECT, space_id,
> + acpi_region_default_handler,
> + acpi_region_default_setup,
> + rgn);
> + rgn->flags &= ~ACPI_REGION_INSTALLING;
> + if (ACPI_FAILURE(status))
> + res = -EINVAL;
> + else
> + rgn->flags |= ACPI_REGION_INSTALLED;
> +
> +out_lock:
> + mutex_unlock(&acpi_mutex_region);
> + if (installing) {
> + if (res)
> + pr_err("Failed to install region %d\n", space_id);
> + else
> + pr_info("Region %d installed\n", space_id);
> + }
> + return res;
> +}
> +
> +int acpi_register_region(acpi_adr_space_type space_id,
> + acpi_adr_space_handler handler,
> + acpi_adr_space_setup setup, void *context)
> +{
> + int res;
> + struct acpi_region *rgn;
> +
> + if (space_id >= ACPI_NUM_PREDEFINED_REGIONS)
> + return -EINVAL;
> +
> + rgn = &acpi_regions[space_id];
> + if (!acpi_region_managed(rgn))
> + return -EINVAL;
> +
> + res = __acpi_install_region(rgn, space_id);
> + if (res)
> + return res;
> +
> + mutex_lock(&acpi_mutex_region);
> + if (rgn->flags & ACPI_REGION_REGISTERED) {
> + mutex_unlock(&acpi_mutex_region);
> + return -EBUSY;
> + }
> +
> + rgn->handler = handler;
> + rgn->setup = setup;
> + rgn->context = context;
> + rgn->flags |= ACPI_REGION_REGISTERED;
> + atomic_set(&rgn->refcnt, 1);
> + mutex_unlock(&acpi_mutex_region);
> +
> + pr_info("Region %d registered\n", space_id);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(acpi_register_region);
> +
> +void acpi_unregister_region(acpi_adr_space_type space_id)
> +{
> + struct acpi_region *rgn;
> +
> + if (space_id >= ACPI_NUM_PREDEFINED_REGIONS)
> + return;
> +
> + rgn = &acpi_regions[space_id];
> + if (!acpi_region_managed(rgn))
> + return;
> +
> + mutex_lock(&acpi_mutex_region);
> + if (!(rgn->flags & ACPI_REGION_REGISTERED)) {
> + mutex_unlock(&acpi_mutex_region);
> + return;
> + }
> + if (rgn->flags & ACPI_REGION_UNREGISTERING) {
> + mutex_unlock(&acpi_mutex_region);
> + return;
What about
if ((rgn->flags & ACPI_REGION_UNREGISTERING)
|| !(rgn->flags & ACPI_REGION_REGISTERED)) {
mutex_unlock(&acpi_mutex_region);
return;
}
> + }
> +
> + rgn->flags |= ACPI_REGION_UNREGISTERING;
> + rgn->handler = NULL;
> + rgn->setup = NULL;
> + rgn->context = NULL;
> + mutex_unlock(&acpi_mutex_region);
> +
> + while (atomic_read(&rgn->refcnt) > 1)
> + schedule_timeout_uninterruptible(usecs_to_jiffies(5));
Wouldn't it be better to use a wait queue here?
> + atomic_dec(&rgn->refcnt);
> +
> + mutex_lock(&acpi_mutex_region);
> + rgn->flags &= ~(ACPI_REGION_REGISTERED | ACPI_REGION_UNREGISTERING);
> + mutex_unlock(&acpi_mutex_region);
> +
> + pr_info("Region %d unregistered\n", space_id);
> +}
> +EXPORT_SYMBOL_GPL(acpi_unregister_region);
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> index a2c2fbb..15fad0d 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -542,4 +542,9 @@ static inline int unregister_acpi_bus_type(void *bus) {
> return 0; }
>
> #endif /* CONFIG_ACPI */
>
> +int acpi_register_region(acpi_adr_space_type space_id,
> + acpi_adr_space_handler handler,
> + acpi_adr_space_setup setup, void *context);
> +void acpi_unregister_region(acpi_adr_space_type space_id);
> +
> #endif /*__ACPI_BUS_H__*/
Thanks,
Rafael
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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