| /* SPDX-License-Identifier: GPL-2.0-only */ |
| #ifndef _KERNEL_TIME_MIGRATION_H |
| #define _KERNEL_TIME_MIGRATION_H |
| |
| /* Per group capacity. Must be a power of 2! */ |
| #define TMIGR_CHILDREN_PER_GROUP 8 |
| |
| /** |
| * struct tmigr_event - a timer event associated to a CPU |
| * @nextevt: The node to enqueue an event in the parent group queue |
| * @cpu: The CPU to which this event belongs |
| * @ignore: Hint whether the event could be ignored; it is set when |
| * CPU or group is active; |
| */ |
| struct tmigr_event { |
| struct timerqueue_node nextevt; |
| unsigned int cpu; |
| bool ignore; |
| }; |
| |
| /** |
| * struct tmigr_group - timer migration hierarchy group |
| * @lock: Lock protecting the event information and group hierarchy |
| * information during setup |
| * @parent: Pointer to the parent group. Pointer is updated when a |
| * new hierarchy level is added because of a CPU coming |
| * online the first time. Once it is set, the pointer will |
| * not be removed or updated. When accessing parent pointer |
| * lock less to decide whether to abort a propagation or |
| * not, it is not a problem. The worst outcome is an |
| * unnecessary/early CPU wake up. But do not access parent |
| * pointer several times in the same 'action' (like |
| * activation, deactivation, check for remote expiry,...) |
| * without holding the lock as it is not ensured that value |
| * will not change. |
| * @groupevt: Next event of the group which is only used when the |
| * group is !active. The group event is then queued into |
| * the parent timer queue. |
| * Ignore bit of @groupevt is set when the group is active. |
| * @next_expiry: Base monotonic expiry time of the next event of the |
| * group; It is used for the racy lockless check whether a |
| * remote expiry is required; it is always reliable |
| * @events: Timer queue for child events queued in the group |
| * @migr_state: State of the group (see union tmigr_state) |
| * @level: Hierarchy level of the group; Required during setup |
| * @numa_node: Required for setup only to make sure CPU and low level |
| * group information is NUMA local. It is set to NUMA node |
| * as long as the group level is per NUMA node (level < |
| * tmigr_crossnode_level); otherwise it is set to |
| * NUMA_NO_NODE |
| * @num_children: Counter of group children to make sure the group is only |
| * filled with TMIGR_CHILDREN_PER_GROUP; Required for setup |
| * only |
| * @groupmask: mask of the group in the parent group; is set during |
| * setup and will never change; can be read lockless |
| * @list: List head that is added to the per level |
| * tmigr_level_list; is required during setup when a |
| * new group needs to be connected to the existing |
| * hierarchy groups |
| */ |
| struct tmigr_group { |
| raw_spinlock_t lock; |
| struct tmigr_group *parent; |
| struct tmigr_event groupevt; |
| u64 next_expiry; |
| struct timerqueue_head events; |
| atomic_t migr_state; |
| unsigned int level; |
| int numa_node; |
| unsigned int num_children; |
| u8 groupmask; |
| struct list_head list; |
| }; |
| |
| /** |
| * struct tmigr_cpu - timer migration per CPU group |
| * @lock: Lock protecting the tmigr_cpu group information |
| * @online: Indicates whether the CPU is online; In deactivate path |
| * it is required to know whether the migrator in the top |
| * level group is to be set offline, while a timer is |
| * pending. Then another online CPU needs to be notified to |
| * take over the migrator role. Furthermore the information |
| * is required in CPU hotplug path as the CPU is able to go |
| * idle before the timer migration hierarchy hotplug AP is |
| * reached. During this phase, the CPU has to handle the |
| * global timers on its own and must not act as a migrator. |
| * @idle: Indicates whether the CPU is idle in the timer migration |
| * hierarchy |
| * @remote: Is set when timers of the CPU are expired remotely |
| * @tmgroup: Pointer to the parent group |
| * @groupmask: mask of tmigr_cpu in the parent group |
| * @wakeup: Stores the first timer when the timer migration |
| * hierarchy is completely idle and remote expiry was done; |
| * is returned to timer code in the idle path and is only |
| * used in idle path. |
| * @cpuevt: CPU event which could be enqueued into the parent group |
| */ |
| struct tmigr_cpu { |
| raw_spinlock_t lock; |
| bool online; |
| bool idle; |
| bool remote; |
| struct tmigr_group *tmgroup; |
| u8 groupmask; |
| u64 wakeup; |
| struct tmigr_event cpuevt; |
| }; |
| |
| /** |
| * union tmigr_state - state of tmigr_group |
| * @state: Combined version of the state - only used for atomic |
| * read/cmpxchg function |
| * @struct: Split version of the state - only use the struct members to |
| * update information to stay independent of endianness |
| */ |
| union tmigr_state { |
| u32 state; |
| /** |
| * struct - split state of tmigr_group |
| * @active: Contains each mask bit of the active children |
| * @migrator: Contains mask of the child which is migrator |
| * @seq: Sequence counter needs to be increased when an update |
| * to the tmigr_state is done. It prevents a race when |
| * updates in the child groups are propagated in changed |
| * order. Detailed information about the scenario is |
| * given in the documentation at the begin of |
| * timer_migration.c. |
| */ |
| struct { |
| u8 active; |
| u8 migrator; |
| u16 seq; |
| } __packed; |
| }; |
| |
| #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON) |
| extern void tmigr_handle_remote(void); |
| extern bool tmigr_requires_handle_remote(void); |
| extern void tmigr_cpu_activate(void); |
| extern u64 tmigr_cpu_deactivate(u64 nextevt); |
| extern u64 tmigr_cpu_new_timer(u64 nextevt); |
| extern u64 tmigr_quick_check(u64 nextevt); |
| #else |
| static inline void tmigr_handle_remote(void) { } |
| static inline bool tmigr_requires_handle_remote(void) { return false; } |
| static inline void tmigr_cpu_activate(void) { } |
| #endif |
| |
| #endif |
